Impact of Airflow on Refrigerant Measurements and Performance
HTML-код
- Опубликовано: 31 июл 2021
- In this class, Bryan teaches the Kalos techs about airflow and how it impacts system performance. He explains the factors that affect airflow and how those contribute to the overall state of an HVAC system. We use training equipment and MeasureQuick to demonstrate these concepts.
On a typical no-cooling call, many techs start with a visual inspection to look for restrictions. These techs will likely check the cleanliness of the filter, blower wheel, and evaporator coil inlet. Some techs also check the return grille, as it may be dirty or have an extra filter. Frozen evaporator coils are also a symptom of poor airflow (frozen evaporator coils also cause even worse airflow).
On the auditory side of inspection, listening for abnormal motor sounds can clue you in on the static pressure, especially when high static pressure affects ECM motors. Alternatively, strange motor noises can tell you about the motor or blower wheel’s health. For example, PSC motors won’t ramp up under high static pressure; abnormal noises indicate bearing wear or a loose hub on the blower wheel.
Customers may cause low airflow in their HVAC systems. For example, customers may close supply air vents to force more air into another room. (To force more air into rooms effectively, an HVAC contractor can cut a duct board so that it flexes and has a small hole, and then they’d insert it into the supply duct to act as a secondary damper. However, this practice may increase static pressure along the way and negatively affect airflow.) Customers may also move furniture in front of the return and obstruct airflow. Pet hair can also plug returns and filters.
Other causes of poor airflow include collapsed or disconnected ducts. Insulation in the unit can also suck up against the blower. (Don’t pull panels off while the unit is running to avoid letting the insulation cause a restriction.) Water in the return can also cause airflow restrictions, especially in flex duct systems. Fire dampers may cause poor airflow in commercial applications. Slipping belts or poorly adjusted sheaves can also contribute to poor airflow.
Before taking any measurements, make sure your gauges have been zeroed out and calibrated against each other. When you have poor airflow, your typical measurements will be either normal or low. You can expect your superheat to be normal to low. Your suction pressure, head pressure, and delta T will also be low. Static pressure is NOT a measure of airflow, but it can tell you about the airflow; you can have poor airflow if the static pressure is good, but the motor may not be producing enough airflow. However, the ULTIMATE indicator of low airflow is a low suction line temperature; any suction line temperature lower than 50 degrees (F) with normal indoor temperature is a likely indication of low airflow.
Some tools that measure airflow include TrueFlow grids, vane anemometers, and hot wire anemometers. However, these are advanced tools, and each one has its limitations. So, the best way to spot a system airflow problem is to perform those inspections with your senses and take your standard measurements.
As air moves over the evaporator coil, it comes into contact with the fins. Heat moves from the air to those fins, as heat moves from warm air to the colder fins. That heat transfer is critical for moving heat from a space, and fins help the evaporator maintain pressure.
When you have low airflow, the compressor amp draw will drop. The reduced pressure indicates that the refrigerant has less mass. The compressor does less work, but it doesn’t get cooled off as easily, and flooding is also possible.
In our class, we used the training equipment to simulate various low-airflow conditions. We also used the MeasureQuick app to profile the equipment, determine our ideal measurement ranges, and display our data. The MeasureQuick app determined that our superheat was hunting and that we were overfeeding our evaporator.
After troubleshooting the unit, we reduced our supply airflow. Our suction line pressure sharply decreased. We then jammed cardboard in the return duct, and our TESP sharply increased. Overall, our suction line temperature decreased sharply, TESP increased sharply, and subcooling increased slightly. MeasureQuick determined that we were running 249 CFM per ton, which indicates very low airflow.
Check out information on the 2022 HVACR Training Symposium at hvacrschool.com/symposium/.
Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschool.com/.
Great training video. Thanks
Hvac school is a gift from god for hvac techs all over
Brian’s got a real passion for this he is a real asset to the industry
thanks for the hard work Brian keep spreading your knowledge it helps a lot Cheers
That dude in the front just eating pizza kills me everytime
That’s not just any dude
That's Jesse, Bert life! He's basically a celebrity.
Awesome, can’t ever beat the video content
That guy is the real deal that’s why he’s allowed to eat pizza how he pleases
Probably the first time he has sat down all day. Too busy until now to eat. Bryan’s face tells you it’s a hot, humid day.
I feel like I m sitting in with all of you guys remembering the good old days when we spend a great 2 hrs..,.talking bout nothing else than AC situations n issues that I had encounter in 20 yrs in so FL fields....great class I got to say this qualifies as a 2 hr of Training School Credit. I got bout 1800 in 5 yrs of Tech Vo School and Union School.Those were the best yrs of my training experience. Being in the field all this yrs I remember the only reason I joined AC Trade.....Was because my wife say to me one day. What you are giving me is not Enough ......so I Joined night School...while doing Bldg. Maintenance during the day.Thanks God I did I never regret this great career and Decision...hope my Testimony help the Newbies. Tnks and Blessings to all.
I was an electrician by trade for twelve years before becoming a computer geek. Landed a job at a university running a Novel NetWare network for its campus libraries student workstations, then moved to the Chemistry Department (knowing _nothing_ about chemistry) to work in electronics repair of research instruments. When the Chair of the Chemistry department offered to send me to refrigeration school, I said, “Not only Yeah, but . . . “ This is the best trade ever! And I’ve learned more from Brian in his videos and others like it (HVACR Videos for one and “Love the burgers” Nor-Cal Dave for another) that keeps on adding to tech school training! Like you, it was the best decision of my career. Keep learning. There’s so much to learn beyond the basics (keeping the basics at your core, of course)!
Just came across a situation like this and now everything makes sense especially the compressor amps. Thank you sir for all that you share and do for the hvac community especially for new techs like me.
Always enjoy your videos thanks for opening up your company to us.
Great class and expert instructor.
I love these informal classes.
Way better than most AC-videos. Covers relevant issues for most air-flow problems, among many obscure others. We've seen at least a dozen of these. We had obscure problem where fan did not work in cold, and eventually discovered an intermittent electrical connection to the evap motor. Very hard to diagnose.
Training classes for your techs it’s definitely a good investment. The better trained they are the more thorough they’ll be and will take them less time to troubleshoot an issue and have it fixed. The company will eventually make more money because of its good reputation. Your employees will be more valuable and better paid. So everybody’s happy.
51:57 - I finally got my head around this concept by thinking of the SH and SC relationship in this way: High SubCool means higher volume of liquid (stacking) in the condenser and high SuperHeat means higher volume of vapor (less room for liquid) in the evaporator.
me too friend! simplicity rules!
I enjoy this, I am on the go all the time and I have no wiggle room to go to class, wathiching this has made me a more efficient tech,
I love to see a company sponsored technician training that is about doing quailty work and theres no mention of SALES! This is so rare and refreshing. Most companies train on selling more crap to homeowners and the guys know very little technical stuff about doing the actual job real well. I traineda bunch of techs in MN about boiler basics and none of them knew the basics! The company owner got frustrated because I didnt go into selling tequniques with the techs. I told the owner none of his techs are competent to run boiler service calls and have no business selling anything to anyone, relating to boiler systems, until they at least know the basics. Needless to say his profit orientation and my quality/competency orientation were enough at odds that I no longer work there.
Or when you ask for technical training and they instead give you an IWAVE sales training 🙃
Really good videos about hvac
Arron has a valid point on bulb , came across a Ruud with it just chillin outside the cabinet homeowner said systems been rocking fine for years 🤙
not an hvac tech, but watching these videos clued me in to filters overly restricting airflow. i had been using merv 13 filters as they were claimed to capture germs, smoke, very small particles. however they were way too restrictive. i tried exhaling air through it, too difficult. so switched to merv 4, and rely on a stand alone air cleaner unit to get the really small stuff.
Hey man, glad you noticed this, most people don't! Although i'd recommend switching to a Merv 7 or 8 next time your filter change comes around. I find that to be a happy medium that most air handlers can handle gusting thru. Your Merv 4 is certainly way better than the Merv 13 that was present before tho since you probably get crazy air change right now.
Great information 👍
HVAC-R & VRV VRF
Coach from India
Hey great series
Thank you for the great content!
Such a great video. Much more than just air flow in this. Must watch for any tech out there!
Great video
Awesome training videos, would love to attend one in person.
Really appreciate your videos very helpful. I do think you got volume/mass flipped in your explanation, but great way to convey the idea.
Love these vids
I repaired one rooftop unit for HVAC, and a restaurant that technicians had claimed was not repairable and condemned it. Among other faults, the major one was that someone had put on a different blower wheel with the fins facing in the wrong direction.
It was secured at the hub with a square headed bolt, which could only be tightened using a wrench from the open side. So I knew it didn’t come from the factory. From my experience with American air filter blowers I remembered how they always had an allen wrench set screw. So I removed the blower wheel and installed that type of setscrew so I could put it back in in the proper position using the Allen wrench through the fins. Besides having the wrong challenge, quantity of R-22, there were other mistakes. Well monitoring the operation absent of that condenser fan started and stopped intermittently after a while. They had replaced the condenser fan motor but the new replacement motor required a ground wire. I’m not sure at this point if it was the neutral they left off, but it did not run constantly as it should. Eventually, I got the unit to work properly, and they were happy at the diner.
Later on, they needed a new exhaust fan and they got a more powerful one and as result they had to buy another air conditioning unit for the rooftop.
Excellent
I am very impressed with how often you teach your student 🧑🎓 I am very excited to start class soon. I know you're in Orlando, do you have a school nearby in port saint, Lucie?
“See how fast the blowy blows”. Fckn love it 😂
Hey Brian! Could you do a video on zone systems and airflow. Also setting the bypass damper static pressure. I feel a lot of systems that are zoned fail prematurely due to airflow issues. Thanks!
@hvac school the new airflow feature can me modified by going to settings and turning on advanced targets. It was switched to allow for more airflow prediction flexibility. If you set it to 350 400 or 450 and it's too far out of range it locks the airflow gauge
I came across a rooftop packaged air conditioner where the blades were facing the wrong direction.
It could only be put in facing one direction with the square head nut for securing it to the motor shaft. I changed it to an allen wrench type set screw & used an allen wrench that could reach through the blades to reverse the blower wheel’s direction of discharge.
Hi I am learning a lot from your classes of those 20+ video's. I would like to have a sequence from 1 to 20 in term or easy to hard, if it comes a text book ,so of speak. And what text book do you recommend?
Thanks in advance
Min 50.....sensing bulb.Found loose and hanging out sometimes to allow txv overfeeding the Evap Coil you are 100 percent correct. Txv bulb also was missdiagnose
Tnks great video
19:40 - I worked on jobs with power supplied from many companies throughout Florida. I have yet to come across a true sine wave. These waves are very jagged, making the peaks look more like the point of a dagger with chunks of material removed in a bad sharpening session: not the rounded peak of a true sign wave.
So if you’re starting a new system up and you wanted to set the fan speed before charging it, how would you go about doing that. Do you take tesp measurements and set it based on the blower chart or can you just rely on the Mq estimates?
Damn, that in one young tech in the back row.
Hi I just got ducted heat pump installed in my lounge ground level with 4 diffuser 200 and got 2 350 return on upper level ceiling so now heating 80 sq Mt open plan lounge take 2 hours. Should I take return from ground level to make faster heating
I've been waiting on you to make this video. It was helpful to understand how airflow affects superheat and suction line temperature. I was hoping that you would also show conditions that would be affected as you blocked condenser coil as well
Clean the coils inside of it how do you clean the coils inside of the Furnace
Do you require to install if the unit is in closet with the stand with no duct on the return
I am watching this for makeup hours at work for professional development training. I’ve watched a bunch. Enjoy each one. That kid in the back looks like he is bored out his mind tho. Just sayin. He”s probably thinking geez dad. Thanks for the father and son time.great video btw.
Hey Brian, around 13:40 you talk about a collapsed duct due to a “splice in the wrong direction”. What do you mean by this? I have some sinking feeling that I’ve been splicing duct wrong.
Spiral over collar, tape, zip. Wrap over collar, tape zip. Am I missing something?
No you aren't missing anything. Have you ever seen anyone splice flex without a pipe between them? Slide the spiral inside the other? This can be done but you can't slide the spiral from the feed over top of the spiral its feeding. Because the air will get between the two pieces collapse the duct its trying to feed in to. The feed side needs to slide into the inside where no airflow restrictions can occur.
Direction of motor , strength of the airflow being able to pull the filter back into the return grille , strength of air coming out vents , amp draw blower motor , bearings out in motor can cause noise or wheel broken , evaporator coil cleanliness , all types of possibilities and I was always told KISS “keep it simple stupid” and check all the basics first and usually can figure the issue out while checking basics from context clues
Nice
Secuencial pulsed dc .1, 2, 3, repeat= cw rotation, reverse 1, 3 pin reverses rotation on ecm motor?
Appreciate the tutorial!
🥃🥃🍺🍺🍺🍇🏌🏻♀️
Stay safe.
Retired (werk'n)keyboard super tech.
wear your safety glasses.
I already have the duct work. I just need a new unit.
We tried charging the one I have, and it didn't last long. It runs, but it just produced warm air.
Also, our unit is kind of small for the age of this house and the sq ft. About 1985 and 1500 sq ft. single rancher with finished basement.
I'm thinking 2 stage would be nice, but I'm not sure it will be worth it
there's like a 6-year-old in the back of the class. hell yeah, kid, rock on
i can say we did not go over this much in our class and in our time all those fancy gauges where not available either ,,,now i am sleepy ,,,,old man needs a nap ,,,,,great class though ,,,,,fun to watch
Added comment. A PWM system is NOT necessarily a VFD drive. We used to design these for other applications. For AC-systems, where the motor is typically a simple 60Hz-motor-design, the PWM always has to be coordinated with variable frequency (thereby requiring a variable frequency), otherwise the motor will burn-up. For typical induction motors, there is a V/F constant which has to be maintained to maintain the magnetic-flux at an optimum level, or optimum efficiency. As such, the SPEED of the motor will always be determined by the FREQUENCY of the drive, and the PWM will change the VOLTAGE to the motor, as required to maintain the motor at correct flux. Multi-meters which can measure the frequency of the AC motor, will show this. At low speeds, the motor voltage MUST be lower than normal. Do not be deceived by this, if you are reading the voltages at a very low motor speed. At high speeds, some drives can actually deliver much-higher voltages to the motor, than normal. Also deceptive. Usually this variablilty range is only about 3-to-1, but in some systems maybe as high as 6-to-1.
I don't think this was mentioned, but if you are working on a communicating indoor system, and communicating UI, but non communicating outdoor system ( infinity or ion systems) making sure you have the correct tonnage programmed into the UI can cause airflow issues
What could be the real problem if the refer defrosts every after some time but inside doesn't cool the staffs
HAHA that front row cracks me up one guy just rolled out of bed the other is ready to head to the beach.
Not me yelling answers at the tv lol
What if we increase condensing fan speed??
That is my George Bush voice and it wasn’t very good.. let’s pretend that didn’t happen… too late it’s on RUclips 😂 great video! Learned a lot.
Head Press in this Inside interior Install is low because Cond Unit is working under probably Conditioned Space Temperatures,,,,,keep that in mind that if out temp is 95 degrees versus 75 in temp the Head press. Would be considerable much lower.
Bert is a hungry man. Lol and his hair looks like he came from a FL hurricane
he was hit by 277 volts , just kidding
Please make some videos VRF UNIT RELATED
i wish one of my grand kids was sitting there just like that kid.
I woke up today wondering what exactly a dirty filter or a broken fan does.
How can I get into a class like this one
Go work for those guys
Awesome video! This content shouof be treated like reading philosophy, one bite at a time, and breaks to allow full digestion. For young'ens at least
"It is my ambition to say in ten sentences what others say in a whole book.”
Friedrich Nietzsche
what would be considered low amp draw for a compressor with low airflow? like 75% of rla? or less?
I was always told 60% or less
Maybe I missed it, and you probably don't have many in Florida, but the secondary heat exchanger on a HE furnace can often be a source of restriction.
If I walked in class with crocks on, my instructor would’ve roasted me lol
👍👍
On perforated ceiling tiles they suck so bad because yes it's a greater area to have air or open plenum return but especially in food courts and malls all that grease from pizza ovens and everything else goes straight up into them and they catch every piece of dirt and then get blocked and in my case you have a operations manager in general manager that's stupid and what do they do they hire in painters to paint the ceiling and they paint right over all of the perforated tiles so therefore there's zero return now
Acomercial refer container is not cooling but defrosts every after some time
unrelated to HVAC:
wtf did the audio editor do to cause the strange reverb?? It's not easy to filter tons of mechanical noises and reverb but those ominous audio artifacts created after every cut are hilarious!
What about when they add more vents in the basement after they decided to finish basement , is this correct to do?
if the system is oversized, yes. Most ductwork is undersized so in reality, no.
Holy shit, spicoli made it to hvac school hahahha
High static pressure can make the compressor go out to
Look like the crew just got done fighting thanos
My observation is that a company needs to pay a trainer and there guys for their time to tech train at least 2 hours a week or the other option is to hire union service fitters who already got all that extra training and just pay the union wages happily because you dont need to do the weekly tech training.
That one guy totally just shows up fir the pizza lol
Wow Eric's head is literally covering me the entire video lmaoooo
Oh also forgot on a p sc fan motor someone set the speed to low
This person making me hungry watching this video.
Check the capacitor on the blower lol
So Marv is trying to break in by posing as an HVAC guy this time?
I heard "very shitty pets" and was like what? Then I realized he said "very sheddy pets" LOL!
Me too lol. But all of the service guys know that there are also some truly shitty pets as well. Love the homeowners who will let the dog piss and shit right next to the condenser and then expect you to kneel right down in it.
25.30 call me sad but I do this. Sorts out the info with Fieldpiece sta2
Like your teaching very much? When you going to talk about mini split
I had a 3 1/2 ton unit with six supplies vents. It was going on defrost every 30 minutes.
16.00. I when to a no cool and found this, so it can happen
These employees totally look like a SNL skit
Low air flow you got a couple times I've come across it where you got dead animals get pulled into the squirrel cage and literally becomes a squirrel cage of death you also get chunks of trash and bags that get pulled down and sucked up and it's on the inside of the wheel you got low air pressure build up where it starts to freeze which then old dirt sticks to it which makes it freeze more there's so many things over 25 years I couldn't even list them on two pieces of paper what I've seen hell I do commercial 200 ton units and my duct works at one time built up static because the turn in veins were under such great pressure because the idiots installed the units incorrectly that it broke off a turn of veins and they went down the ductworking got lodged and we're talking ductwork where you walk down it and then you have to go down onto your knees until you get down to your belly pulling out of 5 ft x 3 ft section of heavy gauge steel is annoying especially for those self-tap screws
Dude in the front eating pizza looks high lol
Guy up front looks like Lucifer from Supernatural
If Bert keeps eating that pizza he s going to get some wet gas in his pants
Your guys statred engaging at min 36.. you keep them.. they got to the point so they can finally say something.
😂😂😂
Hahaaa..dont sue me
Im not even an HVAC tech
Bert wants more pizza
Last ten minute of video was hard to watch. way to many edits adn sound quality suck. Sorry
But don't take lunch breaks lol
There's no shame in a husband who does nothing on weekends? ;)