AIRFLOW TESTING: 8 Ways to Test Residential HVAC Airflows with Corbett Lunsford

[@eddykain4983]

100% legit stuff nicely done. Now why KZbin has failed me by only just now recommending this video is beyond me.

[@HomePerformance]

Hell yeah Eddy! Thanks for the hi five.

[@neilcomparetto5282]

Not my first time watching this video... still one of my favorites of all time!!

[@HomePerformance]

+Neil Comparetto aw shucks brother

[@NatetheHouseWhisperer]

Indeed, super well done.

[@frankgall6]

been watching your videos for a while now and ordering the book now. hope to hear you on hvac school more often. love what you do

[@HomePerformance]

+frank gallina thanks brother! We'll ship your book out first thing this week.

[@bialy100k]

Great idea with the plastic bags - love it :) I spent ~50€ on "better" Chinese anemometer/flow meter and this was horrible un-accurate when measure speed (you can watch my struggles on YT). For range 4-30 mph inaccuracy was up to 5%, but under this number even up to 30%. Above 30mph goes again bad, It was hard to estimate, but no less than 10% around 60mph (for this use car and anemometer on pole+GPS).

[@lakemechanic6930]

That Retrotec DM32 is quite pricey. Can one calculate flow rate from the box & simple manometer pressure drop & save a grand+? If so, what is the equation?

[@jimbergmann3499]

Corbett, Just a few notes/suggestions. The large vane was not used properly or as intended for exhaust fan flow. The vane would be influenced by the rotation of the exhaust fan. There is a flow funnel set made for the vane and a funnel factor that is used when measuring exhaust airflow. In addition, both vanes allow for the input of area to automatically calculate the CFM from the velocity. Second, the reason the first are lower then the last 4 is the last 4 were measured independent of air density or corrected for air density. The Testo vanes actually measure airflow by measuring the number of rotations of the fan which measures airflow independent of air density. The first 4 measurements all measure airflow by measuring the pressure drop across a fixed orifice the fan orifice or a pitot tube array including the powered flow hood. They are all manometers. Air density is affected by barometric pressure, temperature, and relative humidity. I do not believe that any of the instruments you used correct for all 3. What you effectively were able to show is that if air density is not considered or corrected for the airflow readings will be lower than normal. Also while the powered flow hood has been touted as the industry standard, the TAB industry still uses the Pitot Tube as the standard for all airflow measurements. As the ductwork is rarely accessible when testing exhaust fans, a powered flow hood at the exhaust inlet, a vane with a hood, or the exhaust fan flow meter would be the most effective methods for measuring exhaust. The large vane and the small vane used as demonstrated would not be as accurate. The garbage bag while interesting is not an easy or effective method for most applications. Interesting video Jim

[@HomePerformance]

Thanks for the added insight, Jim. We intended for the 75 cfm to be a stand-in for many residential supply ducts and ventilation ducts. Interestingly, we were sent these Testo tools without a very in-depth manual, so it was anyone's guess (unless we have access to you) how exactly they intended the tools to be used. The Pitot is a great choice, I agree, though in residential settings I find there is hardly ever a 8.5 diameter length upstream and 1.5 length downstream free of obstructions.

[@cchurch816]

Tks Jim, was wondering

[@GaiaCarney]

‘...whole house mechanical ventilation device...’ That sounds cool 😎

[@Graham_Wideman]

A collection of methods patiently explained -- nice! Question: After you attached the calibrated downstream fan, you adjusted that fan such that the pressure in the connecting duct was zero in order to get the cfm reading from the resulting calibrated fan setting. OK. But then you left that calib fan attached for all the subsequent tests. I'm pretty sure for all those subsequent tests you could have done them without the calibrated fan in the system, though you might have to make a small adjustment for the air resistance of the short length of duct, right?

[@HomePerformance]

Yes, but the fan provided a sort of termination grille that made the video easier to shoot I guess

[@Graham_Wideman]

@@HomePerformance Fair enough. But in terms of the great value of this video lying in showing several alternative methods using _alternative_ (possibly less expensive) equipment, the fancy calibrated fan is not needed as a prerequisite for the trash bag method, for example .🙂

[@brendahiggins1505]

What if I don’t have option of all this testing equipment?

[@bjs027]

I understand how you are measuring an exhaust fan CFM but why can't you use this to measure CFM at an AC register? Using Retrotec DM32 and a cardboard box.

[@cafedarwin]

I’m setting up a duct for orchid growing and see people use corrugated pvc/aluminum. Will schedule pvc hard pipe (6”) have less turbulence leading to higher cfm down a 12-foot stretch with 400CMF 6” in-line fan? Would a film with dimples adhered to the inner side of pipe cut turbulence at the boundary wall?

[@HomePerformance]

Yes. Good thinking.

[@ucanoe]

Thank you Corbett, excellent video, I would like to know what the proper CFM values are for some house hold appliances…for example I have a range hood that is super noisy and does not seem to draw much air up. Is there a way to test it? and what should a reasonable range hood exhaust CFM be? I can test from the kitchen under the hood or go on a ladder outside and test the output vent?

[@HomePerformance]

Great q, Rob. My book goes into several more detailed bits on this front, but here’s the gist of what you’re aiming for: kzbin.info/www/bejne/r2GbeYKkr8aZg5o

[@umuthevaldogantan1937]

So the Panasonic ventilator is smart and changes its speed depending on the resistance. How can you assure that the ventilator stays at constant cfm with every measurement method. Without the ventilator having a constant cfm I assume you can not compare these measurements because the ventilator will adjust its cfm based on the resistance?

[@HomePerformance]

Great point. None of these methods introduces the kind of static pressure the fan would react to.

[@HomePerformance]

Great point. None of these methods introduces the kind of static pressure the fan would react to.

[@tednor]

Great video! Thank you 🙏

[@mclordhelmet]

I'm trying to verify the CFM based on your cardboard box example. I think you said it was reading 10.5 Pa for the pressure. Was 10.5 Pa the velocity pressure?

[@mclordhelmet]

I was looking at the video and saw the reading of 71.7CFM and 10.9Pa. I'm using equation Q = VA -> A = Q/V = 71.7CFM/837FPM = 12.34in^2. I got 837FPM from V = 4005*Sqrt(0.04376inWC). 0.04376inWC is 10.9Pa converted to inWC. I can't seem to get 20in^2 for the Area of the box hole. Am I doing something wrong?

[@grooveneedle7615]

can anyone provide the dimensions of the RO(s) of the E1 E2 E3 on the TEC Minneapolis Exhaust Fan Flow Meter. i know there "BOX" IS 13 X 16 X 8. wondering if i had a similar sized "TOTE" could i save $$$ ? im not down with walking around with a pizza box and a garbage bag.. Thanks!!!!

[@petermanoj9048]

Dear Corbett, I need to measure air flow in a corrosive channel and it has a temperature measuring from 150oC to 300oC. Can you recommend Fluke or Testo instruments for the same? or give your inputs. Thanks

[@HomePerformance]

+Peter Manoj thanks for reaching out. Unfortunately, my expertise is residential, and your application is very industrial- I have no useful advice to offer. Best of luck!

[@chronic420514]

Sorry to keep troubling you but also could you tell me what model is the ventilator/fan you are using, trying to recreate your test setup. Thanks

[@HomePerformance]

This was a Panasonic WhisperGreen

[@colleend2977]

Thank you so much!

[@HomePerformance]

Quite welcome

[@ThaylorHarmor]

Great video. Anyone know of a solenoid that will divert airflow between two PVC tubes?

[@HomePerformance]

Check out Dwyer Instruments, they may have just what you need.

[@cchurch816]

Like a Honeywell bypass ?

[@robertriho6541]

2:15 wrong. Fan with restricted airflow will increase rpm because you lower motor resistance without lowering motor power. The fan themselves don't have any sensor to registered pressure drops.

[@illustrations7076]

Hi what's happens on amps draw if I restrict suction side of any fan or blower and if I restrict discharge side of blower .bc if we restrict suction it will increase rpm results in increase in amps drawn

[@illustrations7076]

Hi what's happens on amps draw if I restrict suction side of any fan or blower and if I restrict discharge side of blower .bc if we restrict suction it will increase rpm results in increase in amps drawn

[@illustrations7076]

Hi what's happens on amps draw if I restrict suction side of any fan or blower and if I restrict discharge side of blower .bc if we restrict suction it will increase rpm results in increase in amps drawn

[@HomePerformance]

Actually, some fans do- like this one

[@chronic420514]

what model is the that highly calibrated duct testing fan he is using in this video?

[@HomePerformance]

Retrotec Duc Tester 200

[@chronic420514]

@@HomePerformance Thank you

[@PaulLadendorf]

Thanks. Great video. What kind of meter are you using for the pitot tube?

[@HomePerformance]

Paul Ladendorf Any digital micromanometer will do, Paul, but this one is a Retrotec DM-32 Smart Gauge. About $1000.

[@singhmaster4]

Would I be able to use this system to test the air flow for something way more pressured? Like the force of a car or semi truck exhaust? Or can anyone recommend something different?

[@HomePerformance]

Retrotec makes a commercial version that can pressurize up to 20” wc. Or you can use a leafblower ;)

[@singhmaster4]

@@HomePerformance No what i'm looking for is something that can measure the air pressure of a truck exhaust. Something not expansive but simple. I want to measure the flow after cleaning the exhaust filters. But don't want to spend 20 thousand for a machine.

[@HomePerformance]

Just a simple digital manometer and a straight or static pressure probe should be all you need then

[@mauriziob5944]

Out building presented us with a document that showed our extraction EXACTLY reached the minimum for the building regulation, in l/s is 27 cfm. I am so dubious the installation had even been balanced out.... they used the exact vane anemometer in this video, 417. Which I am going to rent to take my own measurements. However i think using the vane with the duct is more accurate and doesn't have to account the profile of the duct. How to enforce the test results to the building company if I find out the building breaches regulations? Thanks

[@HomePerformance]

Great Q, Maurizio. Don’t have a suggestion for you legally, but knowledge is power.

[@11ccom]

Good stuff.

[@HomePerformance]

👌🏽

[@renzmariontorres4470]

Hi. do you have an affiliate program for your products?

[@HomePerformance]

Used to, but not anymore. Would still appreciate your referrals of course!

[@kasonkoelsch6305]

Do you have any videos of pressure pan diagnostics using the DM-32? P.s. Thank you for all the great videos!

[@HomePerformance]

+kason koelsch yes, search for the Home Diagnosis tv show sizzle reel!

[@kasonkoelsch6305]

Hey I appreciate it. I actually realized after asking that it was a stupid question and I already knew the answer. Just had to ask to figure it out i guess lol. Big thanks for the reply!

[@HomePerformance]

No, HerGatiox, that's not how it works- this fan was designed to maintain airflow at a range of static pressures. That's what HVI certification means.

[@flyonbyya]

Great info and presentation...As always Only detail I’d disagree with is: Unless I’m mistaken...motors themselves don’t produce appreciable sound, it’s the design and size of the fan and various methods of sound attenuation that reduce the sone rating.

[@HomePerformance]

Sounds like you might know more about it than me

[@tacoontanadechsittipat5540]

thank you

[@HomePerformance]

👍🏽👍🏽

[@lukeskywalker354]

Don't you think your test would of been more accurate using the flex ducting that most contractors use. What you're using is HVAC ducting. There's going to be less resistance when using that HVAC metal ducting. There are no ridges inside, so inturn there's less air drag. On the flex ducting that most houses have have lots of ridges inside. This will restrict air flow just a little. Also most new houses have the ducting exiting the soffit vents. That also puts a slight bend into the ducting. You need to consider these things.

[@HomePerformance]

Thanks Luke, but none of that actually matters to the test techniques- you can use any of these methods on flex duct too.

[@HerGatiox]

Gearing up? i smell bullshit. I thought that the fun just moves less air which cause less resistance on the rotor, which let the fan to move faster..

[@softhvac3861]

Calculation of aerodynamics on android: www.softhvac.com/hvac-calculator-for-android

[@isotac7789]

Not a law no jail time for not having continuous ventilation in one's home.

[@HomePerformance]

Excellent point, everyone. You also cannot currently be put to death for not having intermittent bath fans, even in the state of California. Forewarned is forearmed.

[@JG-ln1nc]

And I was going to waste $1,000 $ when I can use a trash bag

[@HomePerformance]

You really have to explain yourself though, so it costs you in time spent

[@kinnikunky]

@@HomePerformance LOL! Just don't let the customer see it.

[@becumfreeky]

Mr. Lunsford do you think using a mathematical formula to calculate CFM on a heating appliance has a viable use. For example: gas furnace Output BTU ÷ 1.08 * T∆ Electric Furnace Voltage * Amperage * 3.41 = BTUs BTUs ÷ 1.08 * T∆ I'm fairly new in the HVAC trade and I really want to understand airflow better because moving air is often overlooked and I didn't learn as much about airflow in trade school. Great channel btw.

[@HomePerformance]

+Kevin Carter EXCELLENT QUESTIONS. You CAN calculate for CFM, but there are weaknesses. For instance, don't take for granted that a 60k furnace is eating 60kbtu of nat gas. Clock the meter to be sure. Also, how to test for delta T? Dead center of the ducts? Average? Mean? How many samples? You see what I'm getting at, I hope.