I've been doing research on static pressure to understand it better, and this is the best video I've seen on the subject. Highly recommended to HVAC people.
33 year HVAC guy, who started in Air Balance for 3 years. Your videos rock, and you're an effective communicator. I've attended many classes with brilliant instructors who couldn't instruct. That's not you.
I paid thousands of dollars to go to college for HVACR in order to become an HVACR Technician, and my instructor didn't teach us any of this. We either learned (almost) everything from an online educational program (Cengage Learning) or our book. Our teacher often took days off in order to go fishing. I'm pissed; I learned more from this guy about static pressure (and other sections of HVACR from other people here on RUclips) than I have from my 'teacher'. 🤬🤬🤬 Thank you, Corbett. I actually just watched this video about five times back-to-back. After all, repetition is the basis of all teaching. 😏
@@HomePerformance I agree. I think the teachers' philosophy at school is, "We're just giving you enough to get you started. If you really want it bad enough, you'll go get it." And that alone cost $10,000. Next time, I'll just rely on Google and RUclips, and treat myself to another brand new bike.
As a retired service and training manager for a major brand and an instructor of manual J & D, I ground your video to be excellent, correct, and very well explained. Great job! Airflow and air duct testing is so important as many system failures are traceable back to a faulty duct system. A “ tip” if I may. When drilling into a furnace or air handler beware that there’s insulation ( in many cases) that’s only glued on and any excess pressure from the drill may loosen the insulation causing an eventual failure of adhesion allowing the insulation to start flopping around with some ending up on the evaporator coil. Another way, on furnaces, would be to remove the high limit and go in there. You’ll be between heat exchanger cells right above the blower and get a accurate reading too. This way you will not damage the insulation. Just of course be aware that one leg on the limit is hot with 24 volts, so as not to blow the fuse on the board. Real bummer 😖 This video has very valuable information guys, please use it.
Thanks Wayne! And yes, limit switch hole is better than nothing, but the reading obtained there will be higher than actual. If they can pass ESP with that spot, great, but in my experience installers need every 0.1” wc they can get to be at .54” and round down.
First: thank you for the descriptive and informative video.it was very helpful. I have been doing hvac for 30 years and believe it or not I never considered evaluating static pressures. UNTIL one day I did a change out and removed a zoned damper system including the bypass per customers request and was unable to get my subcooling or super heat correct. It was a nightmare. I called the manufacturer technician support and discovered just how important static pressure truly is. It's not enough just to replace a system without verifying that the ductwork was seized correctly. Now I ALWAYS check static pressures on every job including surveys for new accounts. Be safe everyone
I've been searching for a good static pressure explanation video all over RUclips and none of them are as thorough and precise as yours has been! Thanks for taking the time to explain this procedure step by step.
My instructor gave us topics to research before discussing it, and static pressure is one of them. This cleared up a WHOLE LOT for me! Great explanation! Thank you!
Well done SIMPLE video. We use this in our training (for a few years now) when we are onboarding new team members. Thanks for the content, keep it coming brother.
This is invaluable… I want to incorporate this because very few tradesman take this into consideration in the field, and comfort problems are the hardest things for me to solve. I can fix anything that’s broken but when it comes to humidity issues and the refrigerant levels look good… oh boy I start scratching my head
Greetings Just wanted to let you know that I appreciate the video’s you make. I’m sure you get push back from businesses that, in reality, should be thanking you for the information you provide but instead “they” just want things how “they” want them and not to be checked or questioned. Please don’t get discouraged. Just keep on keeping on. Know that you have thousands of guys that appreciate knowing how things are supposed to be. Hope you and your family are well. Grace and Peace Slick
Great presentation. This helped me get more involved in air flow testing a few years ago. Hence to name, static pressure nerd. I would be interested to see the pressure drops in the return drop!
Awesome! By far the most clear explanation of static pressure I've seen! It's been a while for me and I need to do it next week, so I appreciate the refresher! A few notes: 1. That is a quiet AHU, I couldn't hear it in the video! 2. Don't forget the low limit for TESP, 0.08" WC. I've been finding 0.12" is the bottom on some systems - the second floor doesn't cool for squat below that. 3. The positive/negative thing still messes with me. (I'm a little slow sometimes...) Perhaps talk about the difference or spread between the two? The spread -.38 and +.21 is .59. Like I said, I'm a bit slow sometimes... Thanks again for the refresher, I get to freak out once again while I drill holes in a perfectly good furnace next week!
+Energy Smart Home Performance glad to help my friend. Easiest way to calc the spread is just drop the neg sign at the get-go and add the two together.
Well explained and after watching several times and mapping my system which is different than most, I finally understand the pressures and meanings. Thanks.
Thank you for putting so much effort into what is probably the best and most informative RUclips video of its type. Bravo! And guess what. There's no pre-drilled hole in my system!
Nice video. Very true that most don't check sp. Got a kick out of the 'giant fan' comment! I travelled 9 states for an institutional and industrial sheet metal company living out of a service truck and suitcase. Crane and helicopter picks to get equipment on to rooftops and equipment suites. You could actually crawl into the fans I worked with and pretend you were a gerbil if you were so inclined. Our systems that were designed during the tuberculosis period were set up to bring in 100% outside air, heat it, deliver it to the rooms, and then exhaust it through big vents on the roof. In the 80's and 90's we spent days with saws, Jack hammers, drills, the infamous, back breaking 'wacker', and hammers and chisels opening up primary return air chases, and individual room chases to provide return air - and required smoke and fire dampers. There were variable pitch sheaves and vortex dampers to adjust volume (often upgraded from wooden sheaves and flat belts) Million+ btu burners, oil nozzles (sometimes triplex) that drank gallons per hour, even coal stokers (ever had to clear a coal room to get to an auger's shear pin?), early geo- well water circulated through cooling coils, enormous compressors for DX or chillers, huge pneumatic or motorized outside air, mixing, and exhaust dampers, Chai pull, pneumatic, and now ddc controls, and single draft inducer bearings at power plants that weigh more than an entire residential furnace and dx cooling system combined. Had two boilers in a school in Ashtabula ohio that had come OUT of a great lakes steamer in the 1930's. Had to convert them to gas. The last boiler man in the district that knew anything about coal was retiring-- had that scenario at schools all over as coal was being phased out. Remember back in the 80's when one of our sheet metal guys dropped a tinners hammer from a catwalk from duct big enough to drive through at the Ohio Theater in columbus ohio. Just missed the organ. I was often serenaded by Dennis James on their 'Mighty Morton' while performing pm there (35' × 16' filter area with electronic cells and automatic static pressure controlled feed for oiled prefilter rolls {talk about an itchy job!!}) The low notes on that organ would make your innards quiver like the bass guitarist Chris Squire's low notes in Yes's Starship Trooper!! We subcontracted companies that came in to confirm the balance numbers that our engineers had come up with. Our company had been founded in 1867. After merging with a pipe fitting company it took less than 3 years for the new rape and run business model to run it into the ground. They didn't like that I objected to their business approach. Have worked on that little stuff from time to time-- got cut on one of those itsy bitsy zip screw points or a rough cut sliver of metal just about every time I had to try to squeeze my hands into that stuff or work around that light gauge (aluminum foil!!) duct! Lol. Put some give a damn in your work and you'll build friendships that last a lifetime. Was a great trade.
You got it right! The .59 TESP should and does total your other 4 SP readings. SA duct -.07, Coil - .14, Filter -.19, RA duct -.19 = .59 TESP. As you mentioned, the other readings clearly show where the problem of too high TESP is. Thanks
Very clear demonstration, thanks for posting. I've just determined that my furnace (which was installed by previous owner in 2012) is staved for return air. I found that the heat limit switch was tripping every time the system was kicked into 2nd stage heat. When I remove the panel before the blower the limit switch doesn't trip -- I posit that this allows enough airflow to keep the furnace in operating temperature range. I think the installers never fully tested their installation and now I have to figure out how to solve this inadequate return issue for them. My furnace installation does not have any of the ports you called out as needed in order to make TESP measurements.
I agree with so many others on here that this was one of the best, easy to understand explanations and demonstrations for basic testing of static pressure with some great references to industry standard measurements such as drop across filter and A-coil etc. Thanks for sharing! I'm actually trying to determine airflow in CFM for my 3-ton heat pump system to see if it is meeting the required 400cfm per ton which would be a total of 1200cfm to work properly & efficiently. I'm finding that determining airflow accurately without expensive testing equipment can be a very difficult thing. And the results of low cost instruments can vary widely. So, what I might share for those on this elusive hunt, are 2 things: 1 is figuring airflow by using a similar probe but with additional tubing connection (Pitot tube). It works the same but collects 2 measurements simultaneously static and velocity. To get an accurate test a series of holes (travers) are drilled across a section of ductwork at predetermined spacing and a timed and averaging is done and then a bunch of tedious conversion mathematics which seems like a lot of trouble. The alternative using this instrument is a single hole in center and an averaging multiplier of .9 is used to get within +/-5%. Another method listed below blew me away and I'd like to hear comments on this. It utilizes a simple formula using volts, amps draw and temperature rise to determine airflow. I've included a link to the article library.coburns.com/HVACTechTips/Calculating%20CFM%20Coburns.pdf
We always did static pressure, temperature rise and gas pressure tests on all of our start ups, then recorded the readings and put them in a customer file. If you don’t do this you are not determining if the furnace is running properly and under design conditions
We do it on every start up, every single maintenance just to ensure the system is operating properly and nothing has changed within the system. I love it
I have been doing this for years in the memphis area, I am not only a contractor, but an Instructor at a tech school as well. I try to teach my students these principles to commission units and use a blower performance chart to set proper airflow for A/C. The sad part is the majority of homes run .8 or higher. Those 1" pleated filters are horrible for static. I recommend nothing less than a 2" pleated for single filters at the furnace base. Jack Rise from ACCA taught a class here years ago and called Memphis the land of no return. He was right! After seeing very nice homes with 2x4x16" wall stacks and builders trying to get 2 tons of return in two cavities! The installers in the area have no clue, the builders want the cheapest, and the homebuyers say look at the granite countertops and saltwater inground pool. Next thing I'm telling them the ductwork was done by a doofus because they aren't comfortable.Keep educating! I just replaced a 7 year old system on a new house because the plenum had a 4"x22" hole in it in the attic where it was never sealed! Keep calling out the shoddy work! It's not opinion if there is verifiable performance! Oh, sometimes I can't drill an old furnace in a closet, I normally take out the limit switch for my probe, not ideal, but works!
+Jesse Johnson you rock brother. Keep up the great work in TN- the world needs you calling out doofus work! See you around I hope- we're not far, in Atlanta now!
PS +Jesse Johnson : my 6-week mastermind course might be useful to your students or colleagues HomePerformance.training Starts 4/1 and registration begins 3/1
Jesse Johnson I'm in Nashville and I see a lot of the same. I actually got cussed out the other day by another inspector of all people because I wrote up a 5 ton system pulling from one 20x30 return filter and a 10x15 run. The static pressure on the return alone exceeded .5" which is the max on the system allowance. You just have to walk away and shake your head at some people.
If you study anything from ACCA, you will know now in 2022 with the Air handlers, furnaces and package units, the static pressures can exceed 0.5 without causing any issues. Is it ideal to be 0.5 or below, sure I suppose so. But I have seen systems run just fine at 0.9-1.1 without an issue. Variable speed ECM blowers were practically designed for that. But a properly built system with the right amount of return air, a large filtration system 4-6" filters with good air flow, a good variable speed system properly matched with the ducting design and system functions with be most likely below 0.5 but can safely run much higher. For the homes that are completely finished, and ducting cannot be upgraded, the HVAC system can still be spec'ed properly that could be running 0.5-0.9 without a single hiccup. There are just too many variables to say 0.5 is the maximum these days, but this is a 6-7-year-old video and the 80%-98% units have come a long-ways. This is an outdated video but still has some validity for older systems. Like, don't put in a Filtrete 1900 1" in a single stage 20-year-old 80% system, sure you will have problems. But anything with an ECM blower will run fine but I still don't recommend that ridiculous filter. But also, stop putting on those no MERV rated filters that you can see through that cannot even stop flour. Depending, a MERV 8 is a good average for older systems. If you want to pay a $1 a filter and change it monthly with very little filtration, so be it. It is your stuff, but a MERV 5-6 would be fine for that use. Anyone can add a 5" filtration box to their system and have reduced static pressure and better filtration, no matter what year it was built. Just make sure you have good return air, good intake air and generally you will have a pretty healthy system, if serviced yearly and cleaned properly on your coil, condenser and blower. Maintenance is just like a car, after all, they do cost as much to replace! But these days, you can get some amazing systems for a decent price. I sell my clients the best system possible at the best price. Find a small HVAC company that has good reviews, and you will get better service than some big-name company who advertises on TV or mailers. You get to pay for all their advertising, fancy vans/trucks etc. Make sure they do a full manual J, S and D and get 4-5 quotes and ask neighbors and friends on social media for referrals to friends and family. I promise, if you follow some of these rules, you will have success and be happy. Have a great day!!
@@wojtek-33 Do you mean your furnace or AHU is in the attic? You can buy Honeywell, AprilAire, Trion Bear and many other filter boxes. Or are you talking about return air ducts. You can buy filters that have a lip and the filter extends up into the cavity. One brand is Flow Right. And you get get filters at Filterbuy in the custom sizes. So many options available but I am not sure of your setup.
@@Balticblue93 yeah I'm Texas and a lot of homes have the whole system in the unfinished attic with a ceiling filter box in the living space. Of course mine is on a 10ft ceiling so need a ladder to change. It's a pain and it's an odd 24x36. Just found the ones with the lip but they are pretty expensive and almost none for my size. I look into one of the replacement boxes after taking some measurements on my system, maybe it's fine.
Thanks for your clear, concise explanations! I am a residential remodeling contractor. I am having trouble explaining some of these concepts to a client, who thinks that simply closing off vents to half the house in the winter will save energy, that the furnace burns less fuel/gas when vents are closed, and that static pressure can/will damage the furnace components. They have a single stage unit, no AC. Do you have a video that might explain these concepts? My analogy of "getting 10 pounds of sugar in a 5 pound bag" is not getting the point across 🙂 Thank you!
You might try this one first, Scott- it’s shorter and simpler: Static Pressure Testing for Home HVAC: What, Why, and How in 2 Minutes ruclips.net/video/Ks55DcS1ZgQ/видео.html
I know isn't it crazy how slow the growth is working for someone compared when going out on your own. Thats why I'm out here learning a few things, my employer refrained from me to keep me from fully independent lol well here I come! 😂
To clarify, all A/C is just refrigerant and airflows. The refrigerant PERFORMANCE is affected by airflow, but the pressures in the lines and the ducts don't talk directly to each other.
Great video. Thankfully it confirms they way I test static. That is typically ow I test TESP. One slight difference I usually pullout the high limit switch to get the post-blower pre-coil number.
Thanks, Nate! The high limit switch is not ideal- you get a higher than actual TESP. You will pick up some of the pressure induced by the top half of the heat exchanger- which they do not want you to include in the TESP.
Usually I'll pull the limit if the hole is too big I'll put metal tape to make up the space for the magnetic static probe and of course for accuracy . Not all but alot of times in California at least drilling on the side is a real task sometimes the limit is the only answer . Great video
I tell what man. You're a mentor to industry! Dang ole truth is we're all idiots! What we know we inherited. Inheritance requires discern you know what I'm saying man. Calling out the kind from the swag and tossing the bunk under a bus. There may have been a TESP performed on an AH w/out a hole. Some techs remove the limit switch, and testing from there, but doing this will give you a higher reading because of resistance (top of heat exchanger) I try to replace the filter before I test. 4" media filters w/higher or lower merv values also tweak your #'s. Dang ole beer can cold vets deserve respect, but after 20yrs thinking your right when you were actually wrong. I'd respect the man who pointed out this reality proving to me why I had been mistaken. Corbett I think in the future your name may be as recognized as Bob Vila's was 10yrs ago. So if you become the TV host for this new house? I'm applying for a job!
Hey, just a heads up from someone who checks static pressure often on gas furnaces, there is a hole into the heat exchanger available after the blower that the manufacturers make for us, just remove the primary limit switch, I prefer NOT to drill holes into equipment if it is unnecessary.
+Sightthrough, if you test at the high limit switch hole you will get a higher than actual TESP reading, since you're also picking up the top of the heat exchanger.
Great job Corbett! You are extremely articulate and able to convey complicated subject matter in an easily understandable manner. You could easily be a TV personality on one of the DYI channels! I’m assuming the drilled holes should be sealed using metal tape?
People, it seems like many people struggle with where to probe to measure the coil drop. I would like to share what I have done which is very easy to do. You do not need to drill anything and you do not need to buy the special probe either. Just use the screw hole by taking out a screw. To measure underside of the A coil, I unscrewed one of the easily accessible screws from the triangular A coil cover blocking the underside. To measure the top side of A coil, I unscrewed one of the A coil housing cover screws and measured there. In both cases, I pressed the open end of tubing from the manometer ($35 from Amazon) right against the screw hole tight and read the meter. In my case, I measured 0.16 (top side) and 0.25 (underside) which gives me drop of 0.09 WC. I was afraid my A coil would be clogged up a lot after 26 years of use without cleaning at all but this measurement tells me it is wide open for which I am so happy not having to do the big job of disassembling the whole A coil and cleaning it up and reassembling it. Just for sanity check, I also bought Anemometer ($16) from Amazon and it measured anywhere from 550-800 ft/m air speed out of all the vents which seem very reasonable based on what others measured on brand new system. This sort of confirms that my A coil is pretty clean even after 26 years of use without cleaning at all, which is quite surprising. I did not even replace the filter either. I simply vacuumed the filter every year. I hope I am not dreaming.
@@HomePerformance Hi, thanks for the reply. I understand the probe has holes on the side rather than at the tip to prevent picking up velocity pressure. So, in effect, it is measuring the pressure at 90 degrees from the direction of the air flow, is it not correct? If so, if you press the open end of the manometer tubing right against the screw hole which is on the side of housing, aren't you doing the same thing? It is picking up the pressure at 90 degrees from the direction of the air flow. Is that not right? This is what I figured. If you disagree, I can always verify this by buying the probe and remeasuring.
@@HomePerformance As you recommended, I bought the probe and remeasured the static pressure again today. I had to drill the side of the plenum right above the evaporator because the probe was too thick to fit into the screw hole. I measured 0.15 with the probe and also measured exact same 0.15 without the probe, with the end of the tubing pressed against the hole. This is only 0.01 lower than at the screw hole of evaporator cover I measured previously. This difference could be due to manometer tolerance as well. In conclusion, it seems that measuring at the screw hole just by pressing the tubing against the hole is just as good as using the probe. Anyway it was good experiment to see if there was any air turbulence effect you were concerned about if probe is not used. This proves there was none at all.
@tommason5689 ok, in this specific case with this specific geometry- but can’t really generalize that all systems will test the same way. Good work sleuthing!
I disagree with the idea of not calling those companies back whose stickers are on the furnace. Those companies may be perfectly respectable companies. The problem is the individual technician that came out.
I'm curious. Why do you have a $1500 manometer, but only a Ryobi drill? (Kidding.) Thanks for the video, I'm new to the field, just finished A/C season and I'm heading into furnace season.
Haha, and I still have a few shirts from 15 years ago too. Welcome to the whole house practice, hope you get your hands on a blower door and start showing up the competition!
Brian - estimating total airflow based on static pressure and then comparing it to measured flow with a hood sometimes works. However, there's a lot of inherent inaccuracy which greatly reduces the confidence, and the tighter the ducts the greater the duct leakage inaccuracy. The problem is that whenever you subtract one BIG number from another BIG number, minor % errors in either value get magnified in the final result (estimate). Essentially inferring leakage is not the same as measuring it. A duct airtightness test (duct blaster or aeroseal) is the only way to accurately measure duct leakage. Its referenced in all the codes and is how SMACNA standards do it in commercial ducts.
Hello Corbett, First off, way to nail it, great presentation, period! Please bear with me on my question... I hope it does not appear ignorant. How would I check down flow ( mobile home furnace ) filters are attached to backside of door and in this particular case, this unit is about 22 yrs old and does not have central air. There is an exterior independent a/c unit. The back of the Furnace obviously is in the cabinet ( closet ) all ignition, flame sensor, are internal and completely enclosed. Blower is in your face and completely exposed. Thanks, Jerry
Wow, Jerry, good question, but I don't have an answer for you. No experience with this type of unit. Check out this vid to find a way that might work: ruclips.net/video/9vwmP1T2ReI/видео.html
Thank you, bravo , excellent job at explain in layman's terms so our consumers can get a better understanding of what should be done on every installation. It's too bad the majority of technicians installing furnaces do not even know this, at most they just seen pictures in literature but never had their bosses actually run them through it and explain it to them so it never gets done and the customer usually ends up with an inferior install. Thank you for all your effort and passion to educate people about the subject.
So I am all for static pressure testing and agree, many guys don't take the time. But to tell "homeowners" if there isn't a hole drilled in the side of the furnace you shouldnr call them back is EXTREMELY ridiculous. Let alone a hole drilled into the blower door! Call any manufacturer, your warranty is void by drilling hole. Take coil door apart, add hole in A frame part of coil metal, run probe tubing out through lineset hole, like a professional. Put door back on and then remove air filter(always) and place second probe in duct near air filter by drilling hole in ductwork. DONT DRILL A HOLE IN YOUR FURNACE!!
Thank you for this most informative video. I am NOT hvac saavy,but my understanding of it's basic principles,has now been thoroughly upgraded from OH?,to I understand what your saying. Life is good! Be well,friend.
I disagree with the point you made about not calling a company just because there are not holes driven into the furnaces.There are a static pressure readers into the new furnaces
There are a lot of hard working companies that have been providing exceptional service and hard work and you are telling people not to call them back.It not true
Not well said at all. He's bitten off more than he can chew with that ridiculous assumption. First of all, most systems are not a furnace/cased coil combination. It's usually furnace first with a coil installed in the ductwork above... In those situations, there's never a need to even think about drilling into the furnace casing since the ductwork is readily available. Second, a good tech wants to avoid drilling an ugly hole in the casing of the system where an extra baffle for primary heat exchanger velocity makes it far less desirable to drill into. They will usually remove the high limit switch and use that opening for their test location. They can then simply put the high limit back in place and it leaves no evidence that you drilled hideous holes in a furnace... I'd hate to have a customer see this video and think I didn't go the extra mile when I really went out of my way to make sure everything is within spec. And for warranty purposes, many manufacturers require a start up sheet to be completed by the installer to show it was within the specs for proper coverage.
High limit will give you a higher than actual reading, fyi, because you’re not outside the equipment. Also, having tested this on hundreds of systems (and with confirmation from others who’ve done the same), I’d say 95% of them are outside spec. Maybe you’re not testing enough systems- if all you’re testing is your own work, and you do stellar work, then I’m happy for you.
Mike Krzesowiak as an hvac owner; I agree with the statement. If we don’t test, we don’t know. DMM, Guages, Combustion analyzers and every other tool we own is for TESTING. Gotta test to get the numbers. If people are sore then maybe they need to rethink their check up procedures.
Great video!!! now i understand a little more. I will appreciate your advice though. So, i have a new air handler and new ac condenser unit (replaced).Since the installation 2 weeks ago, air flow has decreased noticeable in the third level of the house only (it's very weak). I have it checked (no testing as shown here whatsoever) but the response of the technician is that it's normal. Now, i wake up in the middle of the night sweating, and I also have two fans in my bedroom. Finally, another company is coming this Saturday to check the "blower" (after doing some research that's how i explained the problem). Which should i "demand" from this other company in order to have the unit properly inspected and diagnosed? Thanks in advance!
Hi Priscilla- sorry you’re having trouble, but glad you found us! You should try and find a diagnostics company that won’t have an agenda of selling you HVAC equipment. Go to: HomeDiagnosis.tv/pro to learn to find these companies in your area.
Hey Corbett. Great video!! I hope you can answer me this though. Every video on you tube shows how to measure static pressure and that it should be at about .5"wc for most residential units. However, I cant find any material on What just the return pressure should be. Or what just the supply should read. In other words, what if I have a read of total static pressure of .7"wc. All I know is that it's high. What pressure should I target in the return or what pressure should I target in the supply? You briefly touched in that .14 is average for the a/c coil and that the filter should be at .1"wc. And then you mentioned that at .19 the return was high and .07 the supply was low. But again I dont know what to target. If you could help me understand this I would really appreciate that. Or point me to material that I can read to further my knowledge in the matter. Thanks!!
Sure- ductwork is designed to pressurize to 0.1” or .08”, that should be ret and sup. And you don’t want TESP to be .5”, you want it UNDER .5”. So .1 for ret duct + .1 for filter + .1 for coil + .1 for sup ducts = .4”
Thank you for this helpful video. I am a homeowner looking to learn. On those pressure probes, it looks like they just face into the airflow and it doesnt matter if the hole is "sealed" by the base of the probe where it enters the ducts or am i wrong on that?
Great video. I've done some drilling into plenums and ducts before for testing but never into a unit and below the coils. Any rule of thumb as to where the coils sit in most units so hitting them when drilling into the units can be avoided?
Hi Corbett. Thanks again for making this video. I've got a quick question. I've got a standard Payne 90% efficient furnace that was installed a few years ago, replacing an old dinosaur that had not been in use for 20+ years. Anytime the heat/ac turns on there's a large 'whoosing' sound from the ductwork (from the air pressure I suspect) and there used to be a 'banging' sound when the unit turned off - that is until I added a cross brace to the air return duct (just put a piece of wood across the inside to hold it in place). After watching your video I suspect that my pressures are all out of whack. Can you suggest some way to test them for a home user like myself (and an avid handyman DIYer) without spending the big bucks on a digital unit like you show in the video? Also assuming I DO find pressure problems (TSP too high for instance) is the fix to install larger duct work? Or is there another common solution? Thanks again for all you help.
+Bob Britton yes, your pressures are almost certainly too high. To experiment, take the blower cabinet's door off and let the unit start with plenty of air thru the open door (you'll need to press down on the black safety switch) and the difference in sound at startup will convince you to get the system tested and fixed, probably with more return duct girth.
Bob, your system may very well have settings on the control board that will adjust blower fan speeds up or down. On my system it is required to turn power off to the system before changing the DIP switches otherwise the changes will not go into effect. You'll have to find the installation literature for your model to decipher your control board settings.
great info for new installations . but watch out for home owners who zone their central system . They shut down all registers in rooms they don't use and shut the doors . You can inform them and readjust but they close them up the minute your down the road
Thank you and I look forward to getting your book. My other question is when dealing with existing ductwork then when you find problems how would you suggest we correct them without creating a huge cost to the consumer?
The consumer gets what they pay for- if they see the benefit, they won’t need a lot of convincing on cost. Several ways to seal ducts, depending on situation.
Great video, my question is: when you check for static pressure do you run ac or only the blower fan, can it be check when the heat is on?, the reason i’m asking this is because multiple speed blowers won’t work on a full speed if you just run the blower by itself, thanks for your time...
+Diego Lopez great Q. In the appendix of my book, there are a few methods for tricking the blower to run in AC mode, which you’re right is generally the highest speed. Important in my opinion to know the performance at different speeds, but if your goal is TESP no higher than 0.5, then yes, always test on high speed.
good question everyone, so if you have a roof top packaged unit and want to calculate its external static pressure, do you consider internal pressure drops due to filters and coil? Or do you only calculate the pressure drop due to duct system?
You need to do this with a wet coil. The wet and dry coil static pressure drops are very different. Also a used filter will have a higher drop. A used 5 (4 3/8) inch filter and wet coil, can often equal more that 0.5 on a large number of furnace and coil arrangements. Fan coils usually include the coil in the internal and therefore provide more headroom. I can provide recommended coil and furnace combination data sheets that will shock you on this topic.
I've been in the industry for a year, I was told that yes you shouldn't have more TESP than what the manufacture says but was told by my seniors that you're allowed a little wiggle room (.1-.15 more than the static pressure) because of the filter. Some customers prefer certain types of air filters that will increase the static pressure. Are my seniors right and what do you do to compensate for the thicker filters?
+Kyle Rae great question! Just think about the fact that it’s a pass/fail test. If you’re over .5 even a little, you risk another pro telling your client you don’t know what you’re doing. The old school guys are used to nobody checking their work, but once your client thinks you lied to them one time, they will never hire you again. Remind them that TESP includes the filter- the filter doesn’t get added later as fudge factor. If a homeowner wants a higher MERV filter, they have to go wider media or upsize the return. Keep up the great work challenging the old rules of thumb!!!
I am working on a tenant complaint about AC cooling not being good enough. This is for a an upstairs duplex apartment unit. The evap is getting nice and cold-maybe too cold. I think the fan speed for the cool is too low. Right now the cool for the motor is on the BLUE (Med-Low). And the heat is on YELOW (Med-High). I alway heard that the cool speed should generally be faster than the heat speed, so Im going to switch the two so the cool is Med-High and the heat is Med-Low. Will this help solve my cooling issue?
Good q, but you have only one data point. I’d want to know temp and RH in the apt, actual airflow thru the indoor coil, whether the unit is sized properly, air leakage of the apt walls, ceiling and floor. You could mess around there for years, or solve the problem in one visit if you test. Check out my interview on the HVAC School Podcast: www.hvacrschool.com/blower-door-testing-building-performance-w-corbett-lunsford-podcast/
Great video but the sad reality is that 90% of homes new or old are running twice that static plus the irritating thing is that all the new higher efficient coils are causing a relatively high static drop out of the box. The manufactures are making it difficult if not Impossible to achieve .5"esp. most of the issues are with furnace and coil applications. Airhandlers usually are easier to keep a .4,.5" esp because there rated with fan and evap coil out of the box.
What a terrific video. That was an excellent explanation. I have a question for you. My ductwork is too small for the furnace that was installed. Would it be acceptable to put an additional return and supply in my basement to help compensate for the inadequate ductwork above? It's an old house and it's literally impossible for me to add any additional ductwork at this point. The only place I can access is the basement and that's where all of the ductwork is easily accessible. Thank you and I look forward to your reply.
+Rick think of it like veins and arteries: if you have high BP because there’s constriction close to your heart, adding another vein and artery isn’t going to lower your BP. You need to enlarge the smallest duct. Upsize the plenums, which are the big trunk lines the ducts branch off from.
The trunks taper after the main trunk in the basement. I want to put these new ducts before they taper. As it is, the basement has no return or feed. I have a 400 cfm deficit, going by simple calculations... Both in return and supply
+Rick just identify where the pressure drops using this mapping technique. Make sure what you add will actually fix the problem, then get proof that it did what you thought it would.
I am planning to use the pressure drop across my air filter to determine when the correct time to change it is. I have a set of pitot tube and required hardware to install them. I plan to but 1 on each side of the filter. That said, this mean one pitot tube will be located in the blower assembly of my HVAC system. Based on where I have seen in your video and others, the static pressure should be somewhat constant. Since this is a home unit, I do not expect a large variation in pressure across the duct and plan to use only 2 pitot tubes. With one on each side side of the air filter, located in the center (side-to-side) of the duct and about 6" into the air flow. Other than ensuring I am on the correct side of the blower fan, is the location of the pitot tube in the blower compartment important for measuring the static pressure?
+Grover D first, I assume you mean just static pressure probe when you say 'pitot tube'- a pitot tube also measures total pressure, which you won't need. I'd sample a few places in the cabinet and all different directions for pointing the probe, but yes, it shouldn't matter much.
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You're the first person to actually explain what static pressure is clearly. Thank you.
High praise- thanks man
I've been doing research on static pressure to understand it better, and this is the best video I've seen on the subject. Highly recommended to HVAC people.
Hey, thanks David! Nice to hear!
Same here & I agree!
Thank you other David!
Great for non hvac professional too
Can the testo be use without the probes.
Such a great video of clearly explaining static Pressure. We get static pressure readings on every call our techs go on. Keep up the great work!
33 year HVAC guy, who started in Air Balance for 3 years. Your videos rock, and you're an effective communicator. I've attended many classes with brilliant instructors who couldn't instruct. That's not you.
WOW, thanks a lot my man! Really appreciate it! You know I get trolled for this stuff sometimes too, so it’s nice to hear the opposite.
I paid thousands of dollars to go to college for HVACR in order to become an HVACR Technician, and my instructor didn't teach us any of this. We either learned (almost) everything from an online educational program (Cengage Learning) or our book. Our teacher often took days off in order to go fishing.
I'm pissed; I learned more from this guy about static pressure (and other sections of HVACR from other people here on RUclips) than I have from my 'teacher'. 🤬🤬🤬
Thank you, Corbett. I actually just watched this video about five times back-to-back.
After all, repetition is the basis of all teaching. 😏
Hey man, sorry to hear. I suspect your experience is not uncommon.
@@HomePerformance I agree.
I think the teachers' philosophy at school is, "We're just giving you enough to get you started. If you really want it bad enough, you'll go get it."
And that alone cost $10,000.
Next time, I'll just rely on Google and RUclips, and treat myself to another brand new bike.
@@ParabellumXdefinitely not uncommon it's crazy how little real life education you get from these schools
This guy does the best Tutorial I've ever experience, and I have been watching him for a good while...
Aw, geez, thanks Yozy!
As a retired service and training manager for a major brand and an instructor of manual J & D, I ground your video to be excellent, correct, and very well explained. Great job!
Airflow and air duct testing is so important as many system failures are traceable back to a faulty duct system.
A “ tip” if I may. When drilling into a furnace or air handler beware that there’s insulation ( in many cases) that’s only glued on and any excess pressure from the drill may loosen the insulation causing an eventual failure of adhesion allowing the insulation to start flopping around with some ending up on the evaporator coil.
Another way, on furnaces, would be to remove the high limit and go in there. You’ll be between heat exchanger cells right above the blower and get a accurate reading too. This way you will not damage the insulation.
Just of course be aware that one leg on the limit is hot with 24 volts, so as not to blow the fuse on the board. Real bummer 😖
This video has very valuable information guys, please use it.
Thanks Wayne! And yes, limit switch hole is better than nothing, but the reading obtained there will be higher than actual. If they can pass ESP with that spot, great, but in my experience installers need every 0.1” wc they can get to be at .54” and round down.
@@HomePerformance - What is the best way to deal with the holes after you have run all the tests?
@darriuscole8544 they make metal plugs, or plastic if you prefer.
First: thank you for the descriptive and informative video.it was very helpful.
I have been doing hvac for 30 years and believe it or not I never considered evaluating static pressures. UNTIL one day I did a change out and removed a zoned damper system including the bypass per customers request and was unable to get my subcooling or super heat correct. It was a nightmare. I called the manufacturer technician support and discovered just how important static pressure truly is. It's not enough just to replace a system without verifying that the ductwork was seized correctly. Now I ALWAYS check static pressures on every job including surveys for new accounts. Be safe everyone
Keep on rocking, William!
I've been searching for a good static pressure explanation video all over RUclips and none of them are as thorough and precise as yours has been! Thanks for taking the time to explain this procedure step by step.
So glad it helps you, +Cesar Aquino !
helped me too. thanks!
+Jose Marcano glad it helped!
Home Performance hey so is a wet coil .07? Or is that dry?
Def dry
My instructor gave us topics to research before discussing it, and static pressure is one of them. This cleared up a WHOLE LOT for me! Great explanation! Thank you!
+mike martinez wonderful! So glad to have helped.
There are a lot of videos and web sites that address static pressure. This video is the best of all of them.
Damn, Louis! Thank you buddy.
Well done SIMPLE video. We use this in our training (for a few years now) when we are onboarding new team members. Thanks for the content, keep it coming brother.
Hell yeah man, thanks for the high five!
This is invaluable… I want to incorporate this because very few tradesman take this into consideration in the field, and comfort problems are the hardest things for me to solve. I can fix anything that’s broken but when it comes to humidity issues and the refrigerant levels look good… oh boy I start scratching my head
Well done 👏
The pressure drop of coil + filter called internal static pressure .
The pressure drop of the duct called external static ptessure .
Nice! I'm an HVAC student and its been a while since my first class. This material is refreshing. Thank you.
That’s great- glad you found us. Hope you subscribe and find all our other stuff too!
Thank you. Finally a Static Pressure video that was clear and concise. Answered all the questions that i should have already known the answers to.
Hey, great to hear- thanks!
Greetings
Just wanted to let you know that I appreciate the video’s you make. I’m sure you get push back from businesses that, in reality, should be thanking you for the information you provide but instead “they” just want things how “they” want them and not to be checked or questioned.
Please don’t get discouraged. Just keep on keeping on. Know that you have thousands of guys that appreciate knowing how things are supposed to be.
Hope you and your family are well.
Grace and Peace
Slick
Hey, thanks Slick- very thoughtful of you to take the time, and always nice to hear.
Much better explanations and demonstration for the layman than most other videos 👍😎
Thanks Bob buddy
Wow think I might actually understand it now. This was much better explanation than others teachings.
Awesome Chris!
Anyone else notice how nice that install is.
Great presentation. This helped me get more involved in air flow testing a few years ago. Hence to name, static pressure nerd. I would be interested to see the pressure drops in the return drop!
Love it! Thanks my friend! More testing courses coming up, both in person and virtual: BuildingPerformanceWorkshop.com
Awesome! By far the most clear explanation of static pressure I've seen! It's been a while for me and I need to do it next week, so I appreciate the refresher!
A few notes:
1. That is a quiet AHU, I couldn't hear it in the video!
2. Don't forget the low limit for TESP, 0.08" WC. I've been finding 0.12" is the bottom on some systems - the second floor doesn't cool for squat below that.
3. The positive/negative thing still messes with me. (I'm a little slow sometimes...) Perhaps talk about the difference or spread between the two? The spread -.38 and +.21 is .59. Like I said, I'm a bit slow sometimes...
Thanks again for the refresher, I get to freak out once again while I drill holes in a perfectly good furnace next week!
+Energy Smart Home Performance glad to help my friend. Easiest way to calc the spread is just drop the neg sign at the get-go and add the two together.
Well explained and after watching several times and mapping my system which is different than most, I finally understand the pressures and meanings. Thanks.
Thank you for putting so much effort into what is probably the best and most informative RUclips video of its type. Bravo! And guess what. There's no pre-drilled hole in my system!
Ha, thank you Stephen, and glad to hear you’ll be installing the first ever test port in your system!
Nice video. Very true that most don't check sp. Got a kick out of the 'giant fan' comment! I travelled 9 states for an institutional and industrial sheet metal company living out of a service truck and suitcase. Crane and helicopter picks to get equipment on to rooftops and equipment suites. You could actually crawl into the fans I worked with and pretend you were a gerbil if you were so inclined. Our systems that were designed during the tuberculosis period were set up to bring in 100% outside air, heat it, deliver it to the rooms, and then exhaust it through big vents on the roof. In the 80's and 90's we spent days with saws, Jack hammers, drills, the infamous, back breaking 'wacker', and hammers and chisels opening up primary return air chases, and individual room chases to provide return air - and required smoke and fire dampers. There were variable pitch sheaves and vortex dampers to adjust volume (often upgraded from wooden sheaves and flat belts) Million+ btu burners, oil nozzles (sometimes triplex) that drank gallons per hour, even coal stokers (ever had to clear a coal room to get to an auger's shear pin?), early geo- well water circulated through cooling coils, enormous compressors for DX or chillers, huge pneumatic or motorized outside air, mixing, and exhaust dampers, Chai pull, pneumatic, and now ddc controls, and single draft inducer bearings at power plants that weigh more than an entire residential furnace and dx cooling system combined. Had two boilers in a school in Ashtabula ohio that had come OUT of a great lakes steamer in the 1930's. Had to convert them to gas. The last boiler man in the district that knew anything about coal was retiring-- had that scenario at schools all over as coal was being phased out. Remember back in the 80's when one of our sheet metal guys dropped a tinners hammer from a catwalk from duct big enough to drive through at the Ohio Theater in columbus ohio. Just missed the organ. I was often serenaded by Dennis James on their 'Mighty Morton' while performing pm there (35' × 16' filter area with electronic cells and automatic static pressure controlled feed for oiled prefilter rolls {talk about an itchy job!!}) The low notes on that organ would make your innards quiver like the bass guitarist Chris Squire's low notes in Yes's Starship Trooper!!
We subcontracted companies that came in to confirm the balance numbers that our engineers had come up with. Our company had been founded in 1867. After merging with a pipe fitting company it took less than 3 years for the new rape and run business model to run it into the ground. They didn't like that I objected to their business approach.
Have worked on that little stuff from time to time-- got cut on one of those itsy bitsy zip screw points or a rough cut sliver of metal just about every time I had to try to squeeze my hands into that stuff or work around that light gauge (aluminum foil!!) duct! Lol.
Put some give a damn in your work and you'll build friendships that last a lifetime.
Was a great trade.
Corbett,
This is a rare find! A superior instructional tool...
Thank you much!
Thanks for enjoying it, Romell!
You got it right! The .59 TESP should and does total your other 4 SP readings. SA duct -.07, Coil - .14, Filter -.19, RA duct -.19 = .59 TESP. As you mentioned, the other readings clearly show where the problem of too high TESP is. Thanks
You are very good at explaining and your teaching is very straight forward and easy to understand, thank you very much
So glad to hear, Yama Zaheer
That is the best explanation of this subject that I have heard. Thank you for sharing this excellent video.
Hey, thanks do much Michael! Happy to hear- hope you’ll dubscribe, lots more where this came from.
Very clear demonstration, thanks for posting. I've just determined that my furnace (which was installed by previous owner in 2012) is staved for return air. I found that the heat limit switch was tripping every time the system was kicked into 2nd stage heat. When I remove the panel before the blower the limit switch doesn't trip -- I posit that this allows enough airflow to keep the furnace in operating temperature range. I think the installers never fully tested their installation and now I have to figure out how to solve this inadequate return issue for them. My furnace installation does not have any of the ports you called out as needed in order to make TESP measurements.
Excellent diagnostic work, Greg!!! Once enough homeowners are like you, the HVAC industry will be a different beast!
I agree with so many others on here that this was one of the best, easy to understand explanations and demonstrations for basic testing of static pressure with some great references to industry standard measurements such as drop across filter and A-coil etc. Thanks for sharing! I'm actually trying to determine airflow in CFM for my 3-ton heat pump system to see if it is meeting the required 400cfm per ton which would be a total of 1200cfm to work properly & efficiently. I'm finding that determining airflow accurately without expensive testing equipment can be a very difficult thing. And the results of low cost instruments can vary widely.
So, what I might share for those on this elusive hunt, are 2 things: 1 is figuring airflow by using a similar probe but with additional tubing connection (Pitot tube). It works the same but collects 2 measurements simultaneously static and velocity. To get an accurate test a series of holes (travers) are drilled across a section of ductwork at predetermined spacing and a timed and averaging is done and then a bunch of tedious conversion mathematics which seems like a lot of trouble. The alternative using this instrument is a single hole in center and an averaging multiplier of .9 is used to get within +/-5%. Another method listed below blew me away and I'd like to hear comments on this. It utilizes a simple formula using volts, amps draw and temperature rise to determine airflow. I've included a link to the article
library.coburns.com/HVACTechTips/Calculating%20CFM%20Coburns.pdf
+Tie Dye thanks for sharing! Here are a bunch of other airflow test techniques: ruclips.net/video/45gX7Jb60JM/видео.html
We always did static pressure, temperature rise and gas pressure tests on all of our start ups, then recorded the readings and put them in a customer file. If you don’t do this you are not determining if the furnace is running properly and under design conditions
We do it on every start up, every single maintenance just to ensure the system is operating properly and nothing has changed within the system. I love it
My hero
Keel up the good work!
Great video. Most installers might be aware of the pressure drop from the filter- if that. They don't know about the other factors such as ductwork.
Thanks as always, Matt
I have been doing this for years in the memphis area, I am not only a contractor, but an Instructor at a tech school as well. I try to teach my students these principles to commission units and use a blower performance chart to set proper airflow for A/C. The sad part is the majority of homes run .8 or higher. Those 1" pleated filters are horrible for static. I recommend nothing less than a 2" pleated for single filters at the furnace base. Jack Rise from ACCA taught a class here years ago and called Memphis the land of no return. He was right! After seeing very nice homes with 2x4x16" wall stacks and builders trying to get 2 tons of return in two cavities! The installers in the area have no clue, the builders want the cheapest, and the homebuyers say look at the granite countertops and saltwater inground pool. Next thing I'm telling them the ductwork was done by a doofus because they aren't comfortable.Keep educating! I just replaced a 7 year old system on a new house because the plenum had a 4"x22" hole in it in the attic where it was never sealed! Keep calling out the shoddy work! It's not opinion if there is verifiable performance! Oh, sometimes I can't drill an old furnace in a closet, I normally take out the limit switch for my probe, not ideal, but works!
+Jesse Johnson you rock brother. Keep up the great work in TN- the world needs you calling out doofus work! See you around I hope- we're not far, in Atlanta now!
PS +Jesse Johnson : my 6-week mastermind course might be useful to your students or colleagues HomePerformance.training Starts 4/1 and registration begins 3/1
Jesse Johnson I'm in Nashville and I see a lot of the same. I actually got cussed out the other day by another inspector of all people because I wrote up a 5 ton system pulling from one 20x30 return filter and a 10x15 run. The static pressure on the return alone exceeded .5" which is the max on the system allowance. You just have to walk away and shake your head at some people.
Never thought I'd learn as much from Jeff Goldblum as I've learned today
Life finds a way
If you study anything from ACCA, you will know now in 2022 with the Air handlers, furnaces and package units, the static pressures can exceed 0.5 without causing any issues. Is it ideal to be 0.5 or below, sure I suppose so. But I have seen systems run just fine at 0.9-1.1 without an issue. Variable speed ECM blowers were practically designed for that. But a properly built system with the right amount of return air, a large filtration system 4-6" filters with good air flow, a good variable speed system properly matched with the ducting design and system functions with be most likely below 0.5 but can safely run much higher. For the homes that are completely finished, and ducting cannot be upgraded, the HVAC system can still be spec'ed properly that could be running 0.5-0.9 without a single hiccup. There are just too many variables to say 0.5 is the maximum these days, but this is a 6-7-year-old video and the 80%-98% units have come a long-ways. This is an outdated video but still has some validity for older systems. Like, don't put in a Filtrete 1900 1" in a single stage 20-year-old 80% system, sure you will have problems. But anything with an ECM blower will run fine but I still don't recommend that ridiculous filter. But also, stop putting on those no MERV rated filters that you can see through that cannot even stop flour. Depending, a MERV 8 is a good average for older systems. If you want to pay a $1 a filter and change it monthly with very little filtration, so be it. It is your stuff, but a MERV 5-6 would be fine for that use. Anyone can add a 5" filtration box to their system and have reduced static pressure and better filtration, no matter what year it was built. Just make sure you have good return air, good intake air and generally you will have a pretty healthy system, if serviced yearly and cleaned properly on your coil, condenser and blower. Maintenance is just like a car, after all, they do cost as much to replace! But these days, you can get some amazing systems for a decent price. I sell my clients the best system possible at the best price. Find a small HVAC company that has good reviews, and you will get better service than some big-name company who advertises on TV or mailers. You get to pay for all their advertising, fancy vans/trucks etc. Make sure they do a full manual J, S and D and get 4-5 quotes and ask neighbors and friends on social media for referrals to friends and family. I promise, if you follow some of these rules, you will have success and be happy. Have a great day!!
What is the location of where you work? I'm sure people reading your comment might be interested in your HVAC services.
How would one go about replacing a 1in filter box in the ceiling with a 5in? They dont seem to exist or i'm just not looking in the right place.
@wojtek-33 you can get a 4” Aprilaire I know
@@wojtek-33 Do you mean your furnace or AHU is in the attic? You can buy Honeywell, AprilAire, Trion Bear and many other filter boxes. Or are you talking about return air ducts. You can buy filters that have a lip and the filter extends up into the cavity. One brand is Flow Right. And you get get filters at Filterbuy in the custom sizes. So many options available but I am not sure of your setup.
@@Balticblue93 yeah I'm Texas and a lot of homes have the whole system in the unfinished attic with a ceiling filter box in the living space. Of course mine is on a 10ft ceiling so need a ladder to change. It's a pain and it's an odd 24x36. Just found the ones with the lip but they are pretty expensive and almost none for my size. I look into one of the replacement boxes after taking some measurements on my system, maybe it's fine.
Great Video. You are a gifted speaker and teacher.
Thanks very much, my friend
Great work Corbett, one simple line from you cleared up my head. Thanks.
+Kamal Hassan so glad to hear!
Thanks for your clear, concise explanations! I am a residential remodeling contractor. I am having trouble explaining some of these concepts to a client, who thinks that simply closing off vents to half the house in the winter will save energy, that the furnace burns less fuel/gas when vents are closed, and that static pressure can/will damage the furnace components. They have a single stage unit, no AC.
Do you have a video that might explain these concepts? My analogy of "getting 10 pounds of sugar in a 5 pound bag" is not getting the point across 🙂
Thank you!
You might try this one first, Scott- it’s shorter and simpler: Static Pressure Testing for Home HVAC: What, Why, and How in 2 Minutes
ruclips.net/video/Ks55DcS1ZgQ/видео.html
Thanks, I learned something and I've been doing a/c for 25 years...
Awesome! Thanks for watching and commenting, Steve!
I know isn't it crazy how slow the growth is working for someone compared when going out on your own. Thats why I'm out here learning a few things, my employer refrained from me to keep me from fully independent lol well here I come! 😂
Best video for furnace system. Would be awesome if you did a video for heat pump systems. Thanks for through easy to understand video.
Thanks Chris, I’ve added it to the list.
Absolutely fantastic explanation! Love it!
Thanks +Stephen!
Stephen Rardon hey Stephen can bad total static pressures cause adnormal refrigerant pressures?
IMon Airflow does effect refrigerant pressures, in my opinion "bad static" is high static which means poor Airflow
To clarify, all A/C is just refrigerant and airflows. The refrigerant PERFORMANCE is affected by airflow, but the pressures in the lines and the ducts don't talk directly to each other.
Always thought the probes need to go with the airflow for accurate readings, what are thoughts Steve?
Great video! Thanks for educating! It made all the pieces fall into place! Sometime a video makes sense when the books dont!
Great breakdown of Total static pressure. Thanks for the video!!
Rock on, +Michael Simi !
great video lets see more on static pressure
Great video. Thankfully it confirms they way I test static. That is typically ow I test TESP. One slight difference I usually pullout the high limit switch to get the post-blower pre-coil number.
Thanks, Nate! The high limit switch is not ideal- you get a higher than actual TESP. You will pick up some of the pressure induced by the top half of the heat exchanger- which they do not want you to include in the TESP.
I conformed that in our shop with a live unit.
Its a pretty consistent .18-2 higher in the heat exchanger.
Super clear & enthusiastic presentation!
Thanks man!
Usually I'll pull the limit if the hole is too big I'll put metal tape to make up the space for the magnetic static probe and of course for accuracy . Not all but alot of times in California at least drilling on the side is a real task sometimes the limit is the only answer . Great video
Agreed, if the limit access is the only way, do it!
I tell what man. You're a mentor to industry! Dang ole truth is we're all idiots! What we know we inherited. Inheritance requires discern you know what I'm saying man. Calling out the kind from the swag and tossing the bunk under a bus. There may have been a TESP performed on an AH w/out a hole. Some techs remove the limit switch, and testing from there, but doing this will give you a higher reading because of resistance (top of heat exchanger) I try to replace the filter before I test. 4" media filters w/higher or lower merv values also tweak your #'s. Dang ole beer can cold vets deserve respect, but after 20yrs thinking your right when you were actually wrong. I'd respect the man who pointed out this reality proving to me why I had been mistaken. Corbett I think in the future your name may be as recognized as Bob Vila's was 10yrs ago. So if you become the TV host for this new house? I'm applying for a job!
+MrTommytabasco wow, thanks for the kind words brother! You made my day!
Thanks for this video! Very informative, especially after my boss asked me what external static pressure is 😁
PERFECT FORM, ZAMBONY
Hey, just a heads up from someone who checks static pressure often on gas furnaces, there is a hole into the heat exchanger available after the blower that the manufacturers make for us, just remove the primary limit switch, I prefer NOT to drill holes into equipment if it is unnecessary.
+Sightthrough, if you test at the high limit switch hole you will get a higher than actual TESP reading, since you're also picking up the top of the heat exchanger.
Great job Corbett! You are extremely articulate and able to convey complicated subject matter in an easily understandable manner. You could easily be a TV personality on one of the DYI channels!
I’m assuming the drilled holes should be sealed using metal tape?
+Paul Mac thanks! We actually are releasing a TV show called Home Diagnosis in 2018! Yes, metal tape works, or metal plugs.
People, it seems like many people struggle with where to probe to measure the coil drop. I would like to share what I have done which is very easy to do. You do not need to drill anything and you do not need to buy the special probe either. Just use the screw hole by taking out a screw. To measure underside of the A coil, I unscrewed one of the easily accessible screws from the triangular A coil cover blocking the underside. To measure the top side of A coil, I unscrewed one of the A coil housing cover screws and measured there. In both cases, I pressed the open end of tubing from the manometer ($35 from Amazon) right against the screw hole tight and read the meter. In my case, I measured 0.16 (top side) and 0.25 (underside) which gives me drop of 0.09 WC. I was afraid my A coil would be clogged up a lot after 26 years of use without cleaning at all but this measurement tells me it is wide open for which I am so happy not having to do the big job of disassembling the whole A coil and cleaning it up and reassembling it.
Just for sanity check, I also bought Anemometer ($16) from Amazon and it measured anywhere from 550-800 ft/m air speed out of all the vents which seem very reasonable based on what others measured on brand new system. This sort of confirms that my A coil is pretty clean even after 26 years of use without cleaning at all, which is quite surprising. I did not even replace the filter either. I simply vacuumed the filter every year. I hope I am not dreaming.
Very cool, but that’s not static pressure testing. A 1-hole tube like a hose picks up velocity pressure as well.
@@HomePerformance Hi, thanks for the reply. I understand the probe has holes on the side rather than at the tip to prevent picking up velocity pressure. So, in effect, it is measuring the pressure at 90 degrees from the direction of the air flow, is it not correct? If so, if you press the open end of the manometer tubing right against the screw hole which is on the side of housing, aren't you doing the same thing? It is picking up the pressure at 90 degrees from the direction of the air flow. Is that not right? This is what I figured. If you disagree, I can always verify this by buying the probe and remeasuring.
@tommason5689 yeah, there’s a lot of turbulence in there, I wouldn’t trust it too much. Only $15.
@@HomePerformance As you recommended, I bought the probe and remeasured the static pressure again today. I had to drill the side of the plenum right above the evaporator because the probe was too thick to fit into the screw hole. I measured 0.15 with the probe and also measured exact same 0.15 without the probe, with the end of the tubing pressed against the hole. This is only 0.01 lower than at the screw hole of evaporator cover I measured previously. This difference could be due to manometer tolerance as well. In conclusion, it seems that measuring at the screw hole just by pressing the tubing against the hole is just as good as using the probe. Anyway it was good experiment to see if there was any air turbulence effect you were concerned about if probe is not used. This proves there was none at all.
@tommason5689 ok, in this specific case with this specific geometry- but can’t really generalize that all systems will test the same way. Good work sleuthing!
I disagree with the idea of not calling those companies back whose stickers are on the furnace. Those companies may be perfectly respectable companies. The problem is the individual technician that came out.
Now we're getting somewhere. Excellent explanation. That's the stuff most AC guy's don't want you to know.☺
Thanks Will
I really like the way you teach and explain so clear for us to understand. Thanks!
Glad to have helped you!
Instead of drilling a hole, I just pull the high limit switch and put my probe there.
Sameee, everyone at the company I work for does it this way.
You get a higher reading there. More punishing to you, the tech, but if you can make it pass there, you’re good
Absolutely the best explanation I've seen on RUclips!!!
Thanks Parnell! Glad you found us!
I'm curious. Why do you have a $1500 manometer, but only a Ryobi drill? (Kidding.) Thanks for the video, I'm new to the field, just finished A/C season and I'm heading into furnace season.
Haha, and I still have a few shirts from 15 years ago too. Welcome to the whole house practice, hope you get your hands on a blower door and start showing up the competition!
I’d like to see how to use this static pressure test along with a flow hood to measure duct leakage.
Good idea Brian- those are two pretty different tests, but there are some interesting ways to link them. I’ll see what we can do.
Brian - estimating total airflow based on static pressure and then comparing it to measured flow with a hood sometimes works. However, there's a lot of inherent inaccuracy which greatly reduces the confidence, and the tighter the ducts the greater the duct leakage inaccuracy. The problem is that whenever you subtract one BIG number from another BIG number, minor % errors in either value get magnified in the final result (estimate). Essentially inferring leakage is not the same as measuring it. A duct airtightness test (duct blaster or aeroseal) is the only way to accurately measure duct leakage. Its referenced in all the codes and is how SMACNA standards do it in commercial ducts.
There’s a device called a duct blaster that does that
very good descriptions in common language that help visualize airflow...
+hvac01453 so glad you liked it!
You tart how to test that furnace really good and I thank you for that.
Tanks Tommy
Hello Corbett,
First off, way to nail it, great presentation, period!
Please bear with me on my question... I hope it does not appear ignorant. How would I check down flow ( mobile home furnace ) filters are attached to backside of door and in this particular case, this unit is about 22 yrs old and does not have central air. There is an exterior independent a/c unit. The back of the Furnace obviously is in the cabinet ( closet ) all ignition, flame sensor, are internal and completely enclosed. Blower is in your face and completely exposed.
Thanks,
Jerry
Wow, Jerry, good question, but I don't have an answer for you. No experience with this type of unit. Check out this vid to find a way that might work: ruclips.net/video/9vwmP1T2ReI/видео.html
Hello Corbett!
Thank you for taking time out to respond and thank you even more for taking additional time with further assistance. Have a great day!
Anytime, Jerry- thanks for following!
@@HomePerformance You bet!
Thank you, bravo , excellent job at explain in layman's terms so our consumers can get a better understanding of what should be done on every installation. It's too bad the majority of technicians installing furnaces do not even know this, at most they just seen pictures in literature but never had their bosses actually run them through it and explain it to them so it never gets done and the customer usually ends up with an inferior install. Thank you for all your effort and passion to educate people about the subject.
Thanks so much for your message, +t lech, I'm happy to be helping the world move forward. Back atcha!
So I am all for static pressure testing and agree, many guys don't take the time. But to tell "homeowners" if there isn't a hole drilled in the side of the furnace you shouldnr call them back is EXTREMELY ridiculous. Let alone a hole drilled into the blower door! Call any manufacturer, your warranty is void by drilling hole. Take coil door apart, add hole in A frame part of coil metal, run probe tubing out through lineset hole, like a professional. Put door back on and then remove air filter(always) and place second probe in duct near air filter by drilling hole in ductwork. DONT DRILL A HOLE IN YOUR FURNACE!!
Couldn’t have explained it any better. Thank you!
Hey, thanks Ronald!
Thank you for this most informative video. I am NOT hvac saavy,but my understanding of it's basic principles,has now been thoroughly upgraded from OH?,to I understand what your saying. Life is good! Be well,friend.
Awesome to hear, buddy! Thanks for your feedback!
What a great video, thank you so much. The furnaces in both of my houses had no ports for measuring?? but they do now.
+john clark you are officially one of the illuminati. Welcome.
Wow!What a great teacher you are. Thanks.
Hey, what a nice thing to say! Thanks!
Fantastic job. I now know what to look for to resolve my problem.
So glad to have helped!
Excellent content and delivery! Thanks.
Thanks for watching, Chuck!
Its late 2019, and this video is still wonderful !! Do you plug the little drill holes when not testing so they won't whistle?
Thanks Bruce! Yep, you can get metal or plastic plugs, or just cover with metal tape.
If the whistle, that's another sign you might have static pressure too high!
I disagree with the point you made about not calling a company just because there are not holes driven into the furnaces.There are a static pressure readers into the new furnaces
There are a lot of hard working companies that have been providing exceptional service and hard work and you are telling people not to call them back.It not true
So you’re saying that most HVAC companies are testing and tracking this? Why do almost all readings exceed the limit?
And I forgot to say this is a very good video! Great job!
+Grover D thanks so much! Glad it helped you!
Excellent video!! is ti more important to have a higher static pressure on the supply or the return?
3:16 "....And that means that you shouldn't call them back. It's that simple." Well said. Well said.
Not well said at all. He's bitten off more than he can chew with that ridiculous assumption. First of all, most systems are not a furnace/cased coil combination. It's usually furnace first with a coil installed in the ductwork above... In those situations, there's never a need to even think about drilling into the furnace casing since the ductwork is readily available. Second, a good tech wants to avoid drilling an ugly hole in the casing of the system where an extra baffle for primary heat exchanger velocity makes it far less desirable to drill into. They will usually remove the high limit switch and use that opening for their test location. They can then simply put the high limit back in place and it leaves no evidence that you drilled hideous holes in a furnace... I'd hate to have a customer see this video and think I didn't go the extra mile when I really went out of my way to make sure everything is within spec. And for warranty purposes, many manufacturers require a start up sheet to be completed by the installer to show it was within the specs for proper coverage.
High limit will give you a higher than actual reading, fyi, because you’re not outside the equipment. Also, having tested this on hundreds of systems (and with confirmation from others who’ve done the same), I’d say 95% of them are outside spec. Maybe you’re not testing enough systems- if all you’re testing is your own work, and you do stellar work, then I’m happy for you.
@@HomePerformance You're inside the equipment in the exact same pressure zone as the location you're drilling into.
Mike Krzesowiak as an hvac owner; I agree with the statement. If we don’t test, we don’t know.
DMM, Guages, Combustion analyzers and every other tool we own is for TESTING. Gotta test to get the numbers.
If people are sore then maybe they need to rethink their check up procedures.
No, the high limit is by definition in the midst of the heat exchanger. It matters.
Great video!!! now i understand a little more. I will appreciate your advice though. So, i have a new air handler and new ac condenser unit (replaced).Since the installation 2 weeks ago, air flow has decreased noticeable in the third level of the house only (it's very weak). I have it checked (no testing as shown here whatsoever) but the response of the technician is that it's normal. Now, i wake up in the middle of the night sweating, and I also have two fans in my bedroom. Finally, another company is coming this Saturday to check the "blower" (after doing some research that's how i explained the problem). Which should i "demand" from this other company in order to have the unit properly inspected and diagnosed? Thanks in advance!
Hi Priscilla- sorry you’re having trouble, but glad you found us! You should try and find a diagnostics company that won’t have an agenda of selling you HVAC equipment. Go to: HomeDiagnosis.tv/pro to learn to find these companies in your area.
@@HomePerformance Thank you so much!!!
Hey Corbett. Great video!! I hope you can answer me this though. Every video on you tube shows how to measure static pressure and that it should be at about .5"wc for most residential units. However, I cant find any material on What just the return pressure should be. Or what just the supply should read. In other words, what if I have a read of total static pressure of .7"wc. All I know is that it's high. What pressure should I target in the return or what pressure should I target in the supply?
You briefly touched in that .14 is average for the a/c coil and that the filter should be at .1"wc.
And then you mentioned that at .19 the return was high and .07 the supply was low. But again I dont know what to target. If you could help me understand this I would really appreciate that. Or point me to material that I can read to further my knowledge in the matter.
Thanks!!
Sure- ductwork is designed to pressurize to 0.1” or .08”, that should be ret and sup. And you don’t want TESP to be .5”, you want it UNDER .5”. So .1 for ret duct + .1 for filter + .1 for coil + .1 for sup ducts = .4”
Thank you for this helpful video. I am a homeowner looking to learn. On those pressure probes, it looks like they just face into the airflow and it doesnt matter if the hole is "sealed" by the base of the probe where it enters the ducts or am i wrong on that?
Have you ever watched How It's Made? It would take a lot to add that whole to the manufacturing process.
Exactly!
Great video. I've done some drilling into plenums and ducts before for testing but never into a unit and below the coils. Any rule of thumb as to where the coils sit in most units so hitting them when drilling into the units can be avoided?
Great video!!! :) I'm a new tech and this opened up my eyes a lot :)
+ve3plo so glad to hear! Thanks for the feedback!
Hi Corbett. Thanks again for making this video. I've got a quick question. I've got a standard Payne 90% efficient furnace that was installed a few years ago, replacing an old dinosaur that had not been in use for 20+ years. Anytime the heat/ac turns on there's a large 'whoosing' sound from the ductwork (from the air pressure I suspect) and there used to be a 'banging' sound when the unit turned off - that is until I added a cross brace to the air return duct (just put a piece of wood across the inside to hold it in place). After watching your video I suspect that my pressures are all out of whack. Can you suggest some way to test them for a home user like myself (and an avid handyman DIYer) without spending the big bucks on a digital unit like you show in the video?
Also assuming I DO find pressure problems (TSP too high for instance) is the fix to install larger duct work? Or is there another common solution?
Thanks again for all you help.
+Bob Britton yes, your pressures are almost certainly too high. To experiment, take the blower cabinet's door off and let the unit start with plenty of air thru the open door (you'll need to press down on the black safety switch) and the difference in sound at startup will convince you to get the system tested and fixed, probably with more return duct girth.
Bob, your system may very well have settings on the control board that will adjust blower fan speeds up or down. On my system it is required to turn power off to the system before changing the DIP switches otherwise the changes will not go into effect. You'll have to find the installation literature for your model to decipher your control board settings.
What an amazing video, so easy to understand Thank you
Happy you found it helpful, Gregory!
great info for new installations . but watch out for home owners who zone their central system . They shut down all registers in rooms they don't use and shut the doors . You can inform them and readjust but they close them up the minute your down the road
+Brian Ellsworth homeowner education is gonna make or break home performance, you're right.
Drill were he told you and become a conductor with the heater element on a non gas furnace unit it will be a moment to remember great video over all
Thank you and I look forward to getting your book. My other question is when dealing with existing ductwork then when you find problems how would you suggest we correct them without creating a huge cost to the consumer?
The consumer gets what they pay for- if they see the benefit, they won’t need a lot of convincing on cost. Several ways to seal ducts, depending on situation.
Thanks man for this amazing class it was easy and understandable
So glad it helped you Kamal!
Great video, my question is: when you check for static pressure do you run ac or only the blower fan, can it be check when the heat is on?, the reason i’m asking this is because multiple speed blowers won’t work on a full speed if you just run the blower by itself, thanks for your time...
+Diego Lopez great Q. In the appendix of my book, there are a few methods for tricking the blower to run in AC mode, which you’re right is generally the highest speed. Important in my opinion to know the performance at different speeds, but if your goal is TESP no higher than 0.5, then yes, always test on high speed.
Home Performance Diagnostic book?
+Diego Lopez bingo! HomePerformanceBook.com
good question everyone, so if you have a roof top packaged unit and want to calculate its external static pressure, do you consider internal pressure drops due to filters and coil? Or do you only calculate the pressure drop due to duct system?
Thank you for creating this video! very well explained
Happy to hear it, Luke! Glad you found us. Lots more like this on our channel.
@@HomePerformance Thanks, I will have a look!
Excellent presentation on subject.
Thanks
You need to do this with a wet coil. The wet and dry coil static pressure drops are very different. Also a used filter will have a higher drop. A used 5 (4 3/8) inch filter and wet coil, can often equal more that 0.5 on a large number of furnace and coil arrangements. Fan coils usually include the coil in the internal and therefore provide more headroom. I can provide recommended coil and furnace combination data sheets that will shock you on this topic.
I've been in the industry for a year, I was told that yes you shouldn't have more TESP than what the manufacture says but was told by my seniors that you're allowed a little wiggle room (.1-.15 more than the static pressure) because of the filter. Some customers prefer certain types of air filters that will increase the static pressure. Are my seniors right and what do you do to compensate for the thicker filters?
+Kyle Rae great question! Just think about the fact that it’s a pass/fail test. If you’re over .5 even a little, you risk another pro telling your client you don’t know what you’re doing. The old school guys are used to nobody checking their work, but once your client thinks you lied to them one time, they will never hire you again. Remind them that TESP includes the filter- the filter doesn’t get added later as fudge factor. If a homeowner wants a higher MERV filter, they have to go wider media or upsize the return. Keep up the great work challenging the old rules of thumb!!!
Your fan motor doesn't care about anything other than the TESP, filter or not.
I am working on a tenant complaint about AC cooling not being good enough. This is for a an upstairs duplex apartment unit. The evap is getting nice and cold-maybe too cold. I think the fan speed for the cool is too low. Right now the cool for the motor is on the BLUE (Med-Low). And the heat is on YELOW (Med-High). I alway heard that the cool speed should generally be faster than the heat speed, so Im going to switch the two so the cool is Med-High and the heat is Med-Low. Will this help solve my cooling issue?
Good q, but you have only one data point. I’d want to know temp and RH in the apt, actual airflow thru the indoor coil, whether the unit is sized properly, air leakage of the apt walls, ceiling and floor. You could mess around there for years, or solve the problem in one visit if you test. Check out my interview on the HVAC School Podcast:
www.hvacrschool.com/blower-door-testing-building-performance-w-corbett-lunsford-podcast/
Great video but the sad reality is that 90% of homes new or old are running twice that static plus the irritating thing is that all the new higher efficient coils are causing a relatively high static drop out of the box. The manufactures are making it difficult if not Impossible to achieve .5"esp. most of the issues are with furnace and coil applications. Airhandlers usually are easier to keep a .4,.5" esp because there rated with fan and evap coil out of the box.
You’re right about the sadness, Marco. You can find air handlers that can fight up to .8” for those occasions- just takes planning ahead.
On some you can remove the furnace limit to gain an access for a test port.
What a terrific video. That was an excellent explanation. I have a question for you. My ductwork is too small for the furnace that was installed. Would it be acceptable to put an additional return and supply in my basement to help compensate for the inadequate ductwork above? It's an old house and it's literally impossible for me to add any additional ductwork at this point. The only place I can access is the basement and that's where all of the ductwork is easily accessible. Thank you and I look forward to your reply.
+Rick think of it like veins and arteries: if you have high BP because there’s constriction close to your heart, adding another vein and artery isn’t going to lower your BP. You need to enlarge the smallest duct. Upsize the plenums, which are the big trunk lines the ducts branch off from.
The trunks taper after the main trunk in the basement. I want to put these new ducts before they taper. As it is, the basement has no return or feed. I have a 400 cfm deficit, going by simple calculations... Both in return and supply
+Rick just identify where the pressure drops using this mapping technique. Make sure what you add will actually fix the problem, then get proof that it did what you thought it would.
Thank you for the quick reply and the advice Corbett.
+Rick of course!
I am planning to use the pressure drop across my air filter to determine when the correct time to change it is. I have a set of pitot tube and required hardware to install them. I plan to but 1 on each side of the filter. That said, this mean one pitot tube will be located in the blower assembly of my HVAC system. Based on where I have seen in your video and others, the static pressure should be somewhat constant. Since this is a home unit, I do not expect a large variation in pressure across the duct and plan to use only 2 pitot tubes. With one on each side side of the air filter, located in the center (side-to-side) of the duct and about 6" into the air flow.
Other than ensuring I am on the correct side of the blower fan, is the location of the pitot tube in the blower compartment important for measuring the static pressure?
+Grover D first, I assume you mean just static pressure probe when you say 'pitot tube'- a pitot tube also measures total pressure, which you won't need.
I'd sample a few places in the cabinet and all different directions for pointing the probe, but yes, it shouldn't matter much.
With all of these tests, would you have pressed the “diff” button on the manometer to see the pressure drop from any one location to another?
By pointing the pitot tube into the flow you are measuring velocity pressure.
No- a static pressure probe cannot measure velocity pressure, that’s why you use it instead of a full blown pitot tube.
I'm one of the few techs that actually do this
Good!