Anemometer + Flow Hood: Discovering a Grille's K-Factor for HVAC Airflow Testing
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- Опубликовано: 14 июн 2015
- Performance testing guru Corbett Lunsford shows you how to find the grille K-factor for every supply register in the house, by using a CFM measuring device like a passive flow hood on just one. Learn to use a $500 large vane anemometer to the fullest by pairing it with a bigger, more expensive instrument selectively.
Tools shown are Testo 417 large vane anemometer and TSI residential flow hood. 
Наука
I appreciate your short videos and have both the flow hood and anemometer but have never used the tools to their full potential Thank You
So glad to have helped! Thanks for watching, James!
Thanks for the video. Stepping into the world of air balancing and your videos are very informative!
Glad to be helping you Jay!
@@HomePerformance Same here. Learning.
I'm so glad you pointed that short coming of the anemometer out for me. I watched a True Tech tool webinar on airflow ,that didn't really explain much about the opening angle and cfm relation. It emphasised that a fan moves a consistent amount of air. No density correction was needed when you test with that Testo anemometer that you had. I internalized that as being the perfect testing method. So I raise my hand..."I am an idiot !" There now I can learn lol
Joseph Quattrocchi HA! So glad my idiocy is rubbing off- and by that I don't mean wearing away. If anything, it's growing on me. More to rub off on other people. All airflow testing is fatally flawed by the fact that air is squirrelly and refuses to be measured. Almost like it's laughing at us. Maybe air is the idiot.
@@HomePerformance Hello Corbett! I have a question about the K factor. In situations where you can’t find the engineering data, could I take a measurement with and without the register in place to find the K factor? Thanks in advance!
it s really important details which you have imparted. i like you show video with formulas
Very well explained. Thank you for the tutorial. I learned alot
+Alexander Gomez so happy to hear!
Great educational video.Thank You
I like the video :) Nice & clean way of explaining
Thanks Naveen
Very detailed information and it is really appreciated. Good Job.
Glad you found us, Randi!
Hi
Heya
Very educational !
I have more knowledge now about it Thanks to You
So glad to hear it- thanks for following!
Good lecture, thanks for your explanation on the k factor and I will like to know how to use the flow hood
You’re welcome, and I recommend starting with the CPS Easyhood.
this is wonderful explanation
Thank you Sam
Good video. I was wondering how you got that vent surface figure. Now my calculations are getting closer. Thanks
solid video. been debating on what tool to get for CFM readings
Thanks for video, based on your experience where you recommend installing the volume dampers, close to the diffuser or closer to the branch take out (Noise related)
Right at the takeoff, if it’s accessible- there’s always the register damper at the end.
أكتر حاجة عجبتني ،
إن حضرتك شبه فؤاد المهندس
بالتوفيق يا هندزة
That’s exactly what I was thinking
Had to subcribe. This information is useful 😎
Great! Glad you found us.
Thank you for the nice demo! I'm not sure it's accurate to assume flow is identical (enough) at two different grille locations to calculate the grill K-factor this way, however. Best to measure velocity AND flow rate on that once ceiling mounted grille - and hope that a variable speed system (if applicable) hasn't changed rates in the meantime. Thanks - MB
He didn’t assume anything. He measured the volume and velocity from one grille and calculated his k factor. He then read the other grille using the k factor already established to get a volume. And you never just hope a fan doesn’t change speeds you make sure that a fan is forced to a constant speed if it is a variable system, otherwise you are just chasing your tail.
Thanks for video
👍🏽
Excellent very helpful
Awesome video
Thanks Steven
I really appreciate it all
Glad you found us, Justus
well demonstrated...! Many a time the Contractors are smart manipulating K factor & work out what suits them & not the design.
Very possible- it's more technique than tool, in my experience
Good stuff !
V informative video. Thanks
Most welcome
Except explanation. Thank you
Thank you to be so helpful with your video tips
Very helpful
Great video
Thanks Jon
what about back pressure compensation? I would take two measurements at a fixed position so with those grilles if using a vane anaemometer and then get the average in m/s. If you then measured one of the slits and multiplied it by how many there were you would get the free area in meters squared. If you then multiply the two together that would give you the flow going through the grille. I've seen so many bodged jobs where people have just assumed that a K factor works for all grilles but it depends totally on the type of grille.
Thank you man I am ready to get out of that tool but I need to know how to use it because my air flow is not even and all registers
Happy testing buddy
If you don't have access to hood to find the k factor what would be the next step? Do K factors vary from grill to grill hugely ?
Do you ever use a hot wire anemometer? or a Pitot Tube Anemometer to measure at the source? If so, do you use a piezometer ring?
Question about changing k factors!
I saw the video and read a bunch of comments. I'm sitting in Sweden and in a house that collects air from toilet. Bathroom, sleeping rooms - most rooms actually except the kitchen - it has its own exhaust. Anyway, I read somewhere heat pumps are getting a bit more frequent in US? Right? Here in the Nordics they are in every house,unless connected to the city common heat. Or living in the countryside. There are some different versions of these heat pumps - like the one in my house called exhaust heat pump.
Inlet air comes through fresh air vents in most rooms, the cold air heats up in-house and gets eventually into the exhaust air nozzles.
That's my problem. These are setup in a way they regulate the volume flow per second individually. Once adjusted but now completely gone. It is the relation I would like to know. But they have all different k factors. The only thing I see is the total flow. That is in range of changing all air in-house in 2 h.
It's very expensive to hire someone for these measurements. One time sure, but if trying to meet the best fit air change / electricity bill - it would be great with a tool for this.
Like measuring the co2 and adjusting the total flow to this (no one home - lower the flow).
The thing with heat pumps in general is they prefer to use as little heat as possible. Reducing air flow when no one is home decrees then compressor speed and less heat needs to go into the floor heating system - and the conversion electricity / heat will be better. Maybe 5:1 instead of 2:1. We'll, in the range. Since the system also make hot tap water it will control the vent if needed.
Long writing - I just wonder (did not check the other videos) if there is a way to compare the vents. I don't need the exact value but would gain insight in the relation between these exhaust vents. I know the total - I set it in the pump m3/h, about 120-250 in our house.
Anyway, nice see som one discussing this. Looking home it's not a subject. I believe we could do so much more to reduce the fossile exhaust (and save money)
Thanks/Lars
Thanks for teach.
No prob
thanks a lot!
Dear Sir , you did calculations very qucik about the resister , can you please explain..
Hi, good info. So you could actually test the diffuser on the soffit with a piece of cardboard that is 24x24 taped to the top of the capture hood, then just cut out a hole big enough to fit the diffuser inside the hole to let the air come thru the hole in the cardboard. Duct tape and cardboard are a air balancers friend on a capture hood. just sayin...
In my experience the method described is good but the correct way would be to pitot traverse the duct supplying the grille for a true volumetric reading. Use that then to determine the K-factor as the airflow hood itself has restrictions.
Enjoyed your video. I am a multi fuel venting technician. ( chimney sweep ). Includes cleaning and servicing dryer vents. Positive and negative air pressure in a home is a major concern with naturally drafting fireplaces and stoves. If you have any videos addressing these issues, I would be interested. Thanks.
Oh my goodness Roger, yes please subscribe and stay tuned.
+59seank This is just an example scenario- you may find yourself having to measure multiple registers, and taking them off and putting them back on could be tortuous. Also, the grille itself will introduce some backpressure, which will affect the airflow- not sure how accurate you could be with that approach.
👍nice explained🙏
Thanks and welcome
hey Corbett
can you please make a video on air flow test on inveter AC and non inveter AC....
+Abid Ali hmmm, that might be good. I'll keep it in mind, thanks!
Thanks for the reply!! I plan to buy your book from TrueTech after Christmas.
If you don’t mind one more question, it’s been years since I was in school and never have had to deal with duct design or residential.
Do most designers just use 0.1 friction loss for supply and 0.5 loss for return?
I’ve never seen anyone use anything else using a ductulator or slide etc
Thanks again and subscribed
I think you mean 0.1 each for both supply and return- enjoy the book!
Do you have a source in ashrae for static pressure loss per foot of ducting? Are there any losses due to the duct created in the video, however small? Thanks for the very informative video.
+fluterampal not sure what duct you're referring to, but every duct creates pressure loss. There are a ton of pressure loss calculators online, but you can see the equations in ASHRAE Fundamentals duct design chapter.
Hi, arent there smaller flow hoods than the one you showed. Also can you clear up the cfm for each register
The first one was 58cfm and you used the formula. The second one was 100 but you plugged in the k factir into testo. Is that correct?
Very useful. So is this the same "K factor" that is used to calculate the effective ventilation rate for dilution ventilation (Q')? Would I be able to take this approach in an industrial setting using both the rotating vane anemometer and balometer for determination of ACH?
I think you might be meaning another K. There are at least 2.
Hi, I have a condensation issue in my brand new house. I discovered this on our first winter here in Washington state. So far my guess is inappropriate ventilation / air exchange rate between intake net free area through vents positioned in the soffit/overhang (the roof’s lowest edge) and exhaust net free area through vents installed at or near the peak of the roof. I am aware that for proper attic ventilation it has to be a balanced 50% intake/50% exhaust. Having said that, what is the best way possible for to measure exchanges rates on this scenario, particularly when I am not measuring fans. What would be a good anemometer and how should I use it? Thank you.
Gabriel, if you mean condensation in your attic, then do NOT add more ventilation. You should airseal the attic floor. Attic ventilation is very low flow, and you won't be able to measure it with any conventional tool.
ruclips.net/video/fPKt35I4MZ0/видео.html
Corbett, it's been informative going through your videos, thank you! But I have a question: why is there a huge discrepancy between the flow hood cfm (58) and the anemometer measured cfm (100) ? You calculated the k-factor using measured values from those two devices, then programmed that number (0.76) into the anemometer - so as far as I can tell the anemometer should have (essentially by definition) given a cfm value that's quite close to 58. What am I missing here?
I tested a different register, Aram- the first one we tested and used to establish the K-factor, then I tested a register two openings and two 90-degree turns closer to the air handler, and we got 100.
Excellent
+Tbone productions you're so welcome! Thanks for watching!
thank you.good
😎
How do you get 58 cfm? I get 76.78 cfm .... if fpm x Cross sectional area = cfm then 351 x 0.21875 = 76.78 (surely!)
So your Grill K-Factor is 75% of .22 sq ft... Therefore, Is your sq ft on this grill .165... And if so did you program your instrument to .165 sq ft to obtain your CFM.......Cheers Tim
Corbett this might be a silly question but I'm going to ask any way. If you use this on a floor supply register can you just remove the register and forget about the k-factor. I seen you on Matt Moreman's video and have followed you since. Thanks
Hi Richard- no, don’t do that. The register induces some restrictive backpressure, so if you take it off you won’t be taking an as-is measurement. You can alternatively use the new CPS Easyhood which is less expensive than either of these tools- see the review on my channel.
Can you please elaborate more about K factor...?
Hi, If you could please make a video on how much cfm is need for a room. I was told that 1 cfm per 1 sq foot but what if the celling is higher like in new homes. Thank you for much for your videos and I learn a lot from it.
Thanks for following, @Yama Zaheer! The video you’re looking for is this one:
Manual J Load Calculations for Heating & Cooling
ruclips.net/video/aCIrbSFWD20/видео.html
Hi. How to check cfm of home vacuum cleaner? What is the best position/distance between the anemometer fan and the airflow enclosure / vacuum cleaner intake head when taking a reading (ft/min) ? Thanks.
I doubt there has been research on the best way to measure a vacuum cleaner- this is your chance to decide for the world!
Cool video. I noticed you had the cieling register damper partially closed. I'm assuming you did this for even distributing of air. I wonder if your k factor would increase if the cfm was 100-120 through the hood test grille. I will have to review the math again to understand how you did that. And I really don't have access to a flow hood.
Joe Shearer Way to open the can of worms, Joe! Yes, you're exactly right- in fact, airflow measurement is generally regarded to be the biggest PITA in the universe, and my buddy Bill Spohn of TruTech Tools is going to be on a quest this year to separate what's POSSIBLE from what's PRACTICALLY USEFUL. Big difference, as you pointed out.
Guys, I'm bringing in the Big Guns- Bill Spohn , are you there?
Home Performance I'll give a thorough answer, but it will be a while as I am traveling this week and busy next week.
Whats this
351--> 58 CFM ?
144 aq.in.=1 Sq.ft. makes sense .
Once you discover the k factor and record the average cfm. Will the cfm amout change as you move the grill adjustment. I mean everybody had a preference for the opening angle.
Joseph Quattrocchi Yes, as Joe Shearer pointed out, this is the failing of the anemometer method.
A++ tutorial..
+Zachary Hayes Sr wow, that's over 100% approval! Thanks brother!
Hi! Do you have a video on how to measure static pressure of ducted fans and blowers?
You know it buddy!
ruclips.net/video/45gX7Jb60JM/видео.html
Those grills are a pretty common size. What would happen if you were to remove the grill (2 screws) and make a measurement --then put the grill back on and make another measurement. Would you be able to calculate the K factor from the difference? Why do you need to know the resistance? Just curious.
The grill actually changes the flow when it's installed. Since that's normal state, removing it and measuring actually doesn't tell you much.
Hi, apart from these sensors you have shown, are there other ones that can also be used to measure air velocity and air flow rate in animal buildings?
thank you.
+Ayoola Jongbo you should watch ruclips.net/video/9vwmP1T2ReI/видео.html and if you want more, read my book!
THANK YOU
Cool, I'm a newer controls tech. Been wondering what k factor is for a couple of months now.
👍🏽
so I don't have the same anemometer so do you put in the k type under area? as .768? or do you just put the area of the vent?
It's math you'll have to do on either the area of the vent or on the CFM you get. Either way, hard to determine without another piece of equipment.
Hi Corbett what is the best method to measure Air Flow in Data centers
Especially Air Flow coming out of Tiles and entering into server racks
+Manish Kumar Singh Your lucky day! I did a Building Forensics Mastermind webinar on exactly that topic! ruclips.net/video/nzjeHADgnW0/видео.html
I know this is a old video hope you still comment I’m building a laminar flow table Which essentially is a large hepa filter in a box with a fan blowing into the plenum of the filter box the filter is 18x24 or 3 sq/ft
Can I just use a large vein anemometer in front of the filter to measure cfm since all parts of the filter should have even flow over it ? Or is there still a K factor because it’s it’s passing through the filter ?
I just need to confirm that i am getting that 100cfm sustained flow through the filter
Hey Warweed, I try to keep up with responding to all comments! You only need K-factor on supplies, not on returns. You can experiment with your readings against the filter vs. an inch or two away for an interesting variation, might be more different than you’d expect depending on your instrumrnt.
Nice video but I'm not very good at math to calculate the K-Factor and is that a testo your using?
Thanks, Rodney- ultimately I don't recommend this technique, and yes, it was a Testo.
Good explanation,,,,I have litle question,,,,I have FCU ,,whit 1.600 CFM SUPPLY ,, whit 4x Register ,,how many CFM I should have FILTER GRILL RETURNS ...? Can I use the vane anemometer or Capture Hood ?
Interesting keyboard technique, my friend. If the 4 returns are all equidistant from the blower then 400 CFM each, right? Any tool can generally measure that range. Maybe I misunderstood you.
Hi, I have a Q. I have no return in one bedroom upstairs and was wondering if I can just extend the return inside the wall up from the floor below. The opennings would be facing opposite directions as the downstairs wall opens South, and the upstairs wall opens North. So the idea is to make enough holes through the wall by removing 2x4's so that I can extend the return to 2nd floor. The question is will that have a negative effect on the return and will it have trouble pulling air from the 2nd floor, seeing as it can easily pull air from the main floor. Hope that makes sense.
I am so sorry, I might be on drugs, but I'm having a really hard time picturing any of this
My experience in HVAC is mostly limited to residential and light commercial installations, but my goal is to someday become a service tech. Air balancing is something that we as installers never do, so it's a big gap that I need to fill in my knowledge of how to get residential systems up to snuff.
So is there any way of figuring out the register's k-factor without having access to a flow hood? I do own the same vane anemometer you show in this video, is there a way to figure it out only using the Testo 417?
Watch the video '8 Ways to Test Airflow', and you'll see that a plastic trash bag actually gives very reliable readings. Bam.
The first register was a 10x4 (approx)
And the second was a 12 or 14x6 .. anyways - do different sizes don’t come into play when determining the k factor ?
If they’re the same design by the same manufacturer, they should have the same factor
Hii
Please tell me wich anemometer is more sensitive. With small vane or with bigger vane, what is the difference between them.
I didn't find anywere.
And thanks for video.
Equally sensitive, in one sense, but the large vane accounts for greater user error. You don't have to keep it aligned in exactly the right way to get the reading.
@@HomePerformance Thank you alot, and happy new year.
Have you ever tested the AAB Smart Tools ABM-100 and ABM-200 air flow/balancing meters? What do you think.
+Grant Meyers No, I haven't worked with those tools yet, sorry! Hope to.
has the smaller unit not got a cone with it to surround the vent completely?
+f137ch100 that's for exhaust only, or return registers
134 fpm x 0.75 kf = 100.5 cfm. So the fpm thru the second grille would be near 134 fpm (if your anemometer does not have cfm).
I noticed that those registers have dampers in them. I was taught that velocity changes with the movement of the damper. For an example wide open would be less velocity and as you close the damper velocity increases and the free area of the grill also lesson's. But I'm no expert on air balance just a rookie. But if what i am saying is true don't this mean your k factor will also change meaning a non accurate reading ???
Being that the damper is against the back of the register.now if the damper is back in the duct aways i would totally by into what you are saying
+Kurt Weems bottom line: there are inaccuracies in every test method. What I do typically in a normal balancing once-over is just test the velocities to ensure 500-700 fpm, then pressure balance between rooms. Measuring or calculating actual cfm is challenging. Btw, the details of this vid met technical ok by Bill Spohn of TruTech Tools, who is one of the top experts on measurement devices.
just need to know the CFM, so I should just set up the device on CFM and whatever I got it will be the actually reading???
Unfortunately no- you don’t know exactly how big the cross-sectional area of the opening is. To get CFM, you multiply velocity (FPM) by area- like a 10x5 grill, or 50 sq in. But the vanes and other metal bits take away from that 50 sq in- that’s the K factor.
thank you for the video. but i have question give me headache, cant find answer🤯🤕😵😵😵
my Anemometer give me 5m/s max speed in my aircon, but after check the my aircon SPECIFICATIONS show 11.3 m3/min?!?!?!?!thats not make sense to me🤔🤔🤔
my aircon still brain new, i make max speed in remote control.
hope you have answer for my ⁉️
If you convert the units, 5 m/s becomes 300 m3/min. It's always in the details!
Odd question; can you make a smaller tapered hood with an access hole for the vane anemometer and get the same results?
They sell that, but it’s really only for exhaust applications or returns. Any capture hood induces some amount of back pressure that screws with your reading- the bigger the hood, the better.
Thanks
Can traverse a return grill when you can.
Off the wall question that you may not even respond to. Lol. So here it goes.
I know NOTHING about a balometer except that I can purchase one at an auction for most likely under $50
It’s a Loflo 6200 and it appears to be in perfect condition. My question is do you think I’d be better off renting this thing? And if so what would you suggest I charge for a rental? Or straight out sell for a profit?
Thank you in advance.
$50 balometer?! Yes please.
Going to show my ignorance here
If the TESP is right we have enough cfm for the unit right? So now you’re making sure we’re sending the right CFM to the right areas for comfort and noise level ?
Right on, Chader
since I cannot afford to buy this tool, can I buy a cheaper version of this off amazon and do the same thing? maybe with HOLDPEAK 866B?
Buy an Easy Hood from CPS Products instead- it's a combination of both these tools. $400.
NYC videos but there is one thing which I didn't understand is from where this 58 cfm comes from? can you explain olz
Maybe I misunderstand your question, but it's coming from the furnace or air conditioner.
Can you determine the k factor by taking a reading with and without the grill in place?
+Mark E Pugliano no, due to the actual flow changing from backpressure.
Thank you for responding
+Mark E Pugliano anytime
Doesn't the flow hood also have a k factor adjustment? I'm not sure when this is necessary...
Good question, but I believe there’s a key difference- the hood measures the total airflow simultaneously, and the anemometer needs the total flow calculated.
I have AC that was repaired but while blowing cold air does not cool the house now. Professionals can not find whats wrong. It was working amazing for 2 years. Thinking it may not be putting out enough CFM. How about this one? HOLDPEAK 866B Digital Anemometer Handheld
Any test data is better than none! Best of luck- you should also check for disconnected ducts.
Played with Anemometer today. Its confusing that the two return airs total about 1400 ft/ min and most registers are putting out 380 to 400 ft/ min. Just 4 registers exceed the 1400 going in. I was expecting total intake to be dispersed across the balance of registers at different rates based on distance and size.
Feet per Minute is velocity - if you want everything to add up, you need to multiply the velocity (FPM) by the cross-sectional area of the duct or diffuser in square feet (e.g., a 12" by 12" grille would be 1 sq. ft.). You can't really add velocities together.
What type of meter are you using on your hood? We use a shortridge 870, 870C.
+Michael Gonzales this one's an Alnor low flow
can we check side through grill air flow with capture hood?
+Karim Alisha not sure what you're asking
Have you used the 417 with the accessory hoods that they offer? If you have, are they worth the extra investment to get quicker results?
Regards,
Ben
+JBH Energy Solutions Ben, I've been told it works much better for exhaust flows, which is not what I need it for, having a flow pan. Honestly, I'd give it a shot if I was sure I'd know how to use it (Testo's manuals are not known for being in depth).
I have a home in which a proper balancing was never done and they are having severe hot and cold spot issues. So my first step in what will most likely be a long process is to get my airflow to match what my manual j calls for. I thought the flow funnel may help speed the process. Thank you for your input it is much appreciated.
Ben
You should check your Manual D calc, Ben- if that's not matching, you may never achieve what the Manual J calc specifies. Check placement of registers against the map.
Duct sizing matches what is called for, placement and layout is another issue. For instance, I have a full 7" duct supplying the kitchen, that has no exterior walls and no ceiling load! There are some rooms I have already told them are lost causes. But I think we will be able to get much better results with a few modifications to supply, increase returns on the second floor and a balance.
Thanks for your help.
Ben
a lot of companies are asking for paper and air flow data any tips on programs
+ernest garcia my reporting software, Automated Performance Testing (APT) Reports, is what I use: buildingperformanceworkshop.com/apt-reports-software/
I need Techs to check new clean RA filter fpm velocities, starting with a popularly used 16X25 filter of various types so we can divide the velocity in fpm into the CFM flow volume to get the filters Ak (open air area).. Example; 800-CFM / 250-fpm = 3.2-Ak. Most filter areas are way undersized as is a lot of duct systems leading to very poor performance in both heating & cooling modes... Publish the results here, this is very important...! Thank you, Darrell AKA ' udarrell '
It's an awesome...
...thanks!
Excellent video! Why not just make a small collector hood from cardboard that CAN fit over small heat registers? All that air would pass through your anemometer and you could probably figure out a constant to convert fpm into cfm. Just my two cent's worth.
Good question, Paul- any box or hood will create back pressure on the airflow, so you won’t be measuring actual airflow under normal operating conditions.
Good day ,pls show me easy for air balance, thanks
How do I calculate CFM withought having to buy the 2000 dollar tool?
$400 CPS EasyHood
'm very excited 😊😊
But I'm somthing missing
sir your launguage English
I'm don't know this language!!!
Only for Hindi speaking me sir
Sorry my friend, I wish I knew Hindi
Won't the bent fins affect the CFM reading?
Yes, but they’re real life
Is this a requirement for new duct work on residential.
Where?