How the squirrel cage blower works

An explanation of how the blower wheel moves air. Also what happens when the blower runs backwards.
This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

[@airfreightwizard]

Omg you just solved the mystery of why the new blower is only creating a tiny amount of airflow!!! Thank you sir!!!!

[@fireteammichael1777]

8 yrs late but great informative video! Very handy little gem!

[@dangerousdan4184]

A simple way to describe how the blower wheel works is to imagine that each of the fins is a forward-facing cup that holds some air. Air has weight to it. As the wheel rotates, centrifugal force throws that air outward, away from the blower wheel. This creates a void or low-pressure area where that air was, so atmospheric pressure naturally pushes new air from inside the wheel into that space, and the process repeats. If ran backwards, the cups of the fins can't hold the air to get it up to speed, it simply slides off the backside of the fins prematurely instead. Motor horsepower is utilized to get that new air spinning, and therefore, the more air that is allowed to move thru the blower, the more horsepower required to move it. That is why your Shop Vac speeds up when you block off the hose, less load on the motor allows it to speed up. A centrifugal water pump, such as a sump pump, works the same way, and also uses less of the motor's power as the flow is restricted.

[@grayfurnaceman]

Very good explanation GFM

[@grayfurnaceman]

Certifications sometimes tell how well you take tests. I have given many of the cert tests, but I would sometimes not perform as well as a neophyte in the industry. Thanks for the support. GFM

[@edwinmantanico6355]

good simple tips, experience is the king of all certifications. thanks for your share of knowledge

[@slamdvw]

Even the wheel end for end (if it will fit in the housing) but turning the correct way (towards the discharge port) won't move much air. Nice demo!

[@donaldwalls3051]

I have a vintage dual squirrel cage range hood that I removed to clean. I neglected to label the two cages. Now I’m stumped as to which side they should to be mounted. I’ve tried both directions and air is moving. I’ve looked at Google and KZbin but I’m not understanding the information

[@robertsell8717]

Ty you just helped me figure out to switch the powered contracts

[@robertsell8717]

Powered = Pre wired

[@grayfurnaceman]

I will be doing a series on motors and replacement as soon as I get the time. GFM

[@my95vfr]

how do I check the amp draw on these. i have a amp clamp just not sure what wire to clamp it on. i have 3 total fans. 1 is a 110 volt, that one is easy. i have 2 that are 220 volt and im not feeling confident that i am checking them correctly.

[@geojor]

informative video, thanks...

[@alwaysoutdoors7001]

Would you have any idea if it's better to have more space around the squirrel cage or less space?

[@electriccar3253]

inside or outside the blower housing? GFM

[@jimbola77]

Very Very nice!!! Good info thank you.

[@sandykoval3665]

Can the center metal plates come out of the track? And if so, can they be put back in?

[@SombraLocs]

Do you have a video on how to troubleshoot and replace blower motor?

[@jeremyhaag4506]

Where should i place squirrel cage in relation to duct housing inlet for best performance? If i move cage on shaft closer to inlet wall will I get better sealing properties? I have ton air coming out non motor side inlet.

[@grayfurnaceman]

I set it in the center of the housing. GFM

[@mikethemoneymaker]

You know those 1500 Watt Infrared Heaters like Eden Pure....Any idea how many CFM of air they move and what their Amperage draw is?

[@CoolasIce2]

Good shizzle on the bo dizzle.

[@whattodo5416]

Dear GFM, How did you manage to reverse the direction? Did you change the wiring to get capacitor series with running windings instead of starting windings? thnka you..

[@MaryByamSmith]

Vibration/loud noise started after semiannual HVAC maintenance-air conditioning Spring to replace filter and whatever else they do. Serviceman came back and told me adjusted shaft on blower wheel which immediately corrected loud noise when blower running with air conditioner but not with humidifier or heater. This lasted for few days and now sound is back again. They will come back tomorrow. First they said it is because old system-system is fairly new with only 4 seasons of heat/cold use. Is it likely need to replace full squirrel cage/motor?

[@grayfurnaceman]

You may have lost a blower wheel weight during the service. Means a new blower wheel. GFM

[@MaryByamSmith]

Turns out blower motor was culprit-where wheel attaches to shaft in motor. They replaced both motor and wheel as it was in warranty.

[@ProjectDreamCatcher]

Great video. I have a related question. If the squirl cage is turning backwards, how does it affect the in- house air intake where the filter is? In other words, I'm not getting much stregnth out of the cooling vents but a LOT of suction where the filter is? (pretty much grabs it out of my hands!)

[@grayfurnaceman]

If the cage is turning backwards, it will move no air. On the suction, if there is high suction, there is no problem with supply. Either the filter is plugged or a new filter has excessive pressure drop. GFM

[@ProjectDreamCatcher]

@@grayfurnaceman Thanks for the reply. I had a feeling that suction was GOOD news. The system is for a 1990 mobil home (all-in-one outside unit) with air vents in the ceiling (Florida). Since I've never checked the duct work, that's probably it (not much room up there!). My squirrel cage makes a different kind of buzzing hum every now & then only when it starts. And then after many on & off tries (as if warming up) finally kicks in full. But I'm afraid to shut it off because it will probably do it again. I replaced the dual capacitor and seemed to do the trick for about 3 days until I heard the problem again? Is there a way to check the capacitor wilth only a multimeter that doesn't have a capacitor setting? I just have an ETEC 10709. I'm about to spring for a new motor (save the old one & make an exhaust fan!!!). Thanks for your video & time sir.

[@TheEDFLegacy]

Here's a good question for you; I've got a small squirrel cage fan that's working fine. However, I'm attempting to hook it up to a small tube, and get some significant output of wind through it. However, when I attach it to the smaller pipe (after using a funnel shape to reduce the size), I noticed that a good part of the air will go out of the top, while the wind blowing through the pipe is relatively minimal. It seems to be 'backfiring', so to speak. Do you know how I can do what I'm attempting?

[@grayfurnaceman]

These fans are capable of working against a specific amount of back (static) pressure. When you exceed the pressure, the air simply stops. Unfortunately, there is really not much you can do except find a fan that works with higher back pressure. Hope this helps. GFM

[@hoodelves]

Is it the same theory for amp draw on a backwards incline fan? I service kitchen exhaust fans , and find many are spinning backwards.

[@grayfurnaceman]

No, the propellor fan will run with reduced amp draw but not as much as the squirrel cage fan. GFM

[@Cjt99]

Could you use this type of blower in a home made dust collection system? Would the intake restriction stall or over heat the motor? What HP motor would you suggest?

[@grayfurnaceman]

You can. The wheel is not designed for dust collection so you will have to clean the wheel periodically. Intake restriction will reduce the load on the motor. HP depends on the size of the system. GFM

[@arthurcipolla8469]

You mention that they seem a little "backwards". Do you mean that the direction of rotation should be where the convex part of the blade is on the leading direction of rotation?

[@grayfurnaceman]

Sorry about being so long in getting back to you. Yes. I know why they do what they do because the blade is a wing and it pulls a vacuum behind the bulge, but it just looks wrong. GFM

[@albertbrown1433]

which is the best company on the internet to order parts for you air handle like a blower motor for a american standard air handler

[@grayfurnaceman]

I can't say I have any good recommendations. GFM

[@romanmartinez3873]

Hello so theres a swamp cooler on a mobile home im working on however when turned on. Shaking occurs and the ceiling underneath shakes as well. What can be the issue and resolution?

[@grayfurnaceman]

Probably either a bearing problem or the blower wheel is out of balance. You can check the wheel for dirt or trash. GFM

[@wayneparham5542]

How do you know the blower wheel is on the shaft in the right direction.

[@grayfurnaceman]

If you can tighten the set screw without going thru the wheel blades, you are ok. GFM

[@TheRattleSnake3145]

You need to reverse the shroud if you also reverse the rotation, of course the way you reversed didn't work as well.

[@grayfurnaceman]

I just switch the wires that say they are the wires to switch to reverse rotation. lol Not all motors are designed to switch rotation. Most oem motors are not. GFM

[@rob25910]

Question: My original squirrel cage blower wheel lasted 23 years. It separated from the shaft. Anyway, I had it replaced with a new part. It just went today after only 6 1/2 years. The same thing happened. It separated from the shaft. My HVAC repairman says it's pretty rare for this part to go & doesn't know why it broke so quickly. He checked the shaft & said it's not "out of round." He also saw the wheel had been balanced as we could see the weights on it. The motor bearings are fine & are the original ones. What are your thoughts on why the original wheel lasted 23 years & the new replacement wheel only lasted 6 1/2 years?

[@grayfurnaceman]

No real help here. Unless it was vibrating. It is the most common blower failure. GFM

[@rob25910]

OK. No worries. Thanks.

[@4vinos]

Look at my question (4vinos) Hope I can get my question answered.

[@4vinos]

I was told you can only run these in the shop for no more than 2 hours. This is because the blower has no air "restriction" and this causes the motor to over heat. He mentioned a word when this happens but I forgot. Is this true? Can I use this fan as long as I want without "heating" the motor? Thank you for taking time in explaining how this fan works.

[@grayfurnaceman]

The fan is designed to run against some static air pressure. Without that resistance, the fan may overheat. If you want to operate the fan in open air, you can reduce overheat by blocking part of the discharge. GFM

[@4vinos]

You are a breath of fresh air. Your prompt response is appreciated. Many take a long time to respond if they ever do. Keep up the good work.

[@grayfurnaceman]

Thanks for the support. GFM

[@TrueNorthModels]

I am researching building a small hobby airbrush paint booth and I have heard that I can use a squirrel cage blower to extract the paint particles and fumes. My question is, can you have the squirrel cage blower situated so that it creates a draw instead of pushing air. Cheers

[@grayfurnaceman]

Wayne Osborne You bet. Your inlet is at the hub. Depending on the blower, they will pull up 1/2" water column. Hope this helps. GFM

[@TrueNorthModels]

Thanks for the information, just one more option. Cheers

[@luisfernandotorres4354]

the blower wont start what is the problem

[@grayfurnaceman]

Give me make, and model and I will try. GFM

[@TonyStark20]

what is at the purpose of a squirrel cage?

[@grayfurnaceman]

The squirrel cage blower wheel is a design that can supply air flow against resistance to flow. Its called static pressure. The propellor fan will not flow against resistance. Hope this helps. GFM

[@ANtn1969]

its used to train racing squirrels

[@thespiritof76..]

Will an x13 motor run on 24v alone at its rated 1050rpm?

[@grayfurnaceman]

No. The 24 volt is just for controls. It must have either 120 or 240 volts to operate. GFM

[@thespiritof76..]

Thanks man.. Mine is a 220, it seemed to good to be true even though a 100 different professional videos on here claim it to be a DC motor

[@grayfurnaceman]

@@thespiritof76.. It is a 3 phase DC motor. Single phase is changed to DC then is separated into 3 phases by the electronics. GFM

[@thespiritof76..]

grayfurnaceman ok, I have the control that was on the side of the blower, first thing I noticed was the transformer.. that's what starting me to thinking. I work and deal in sound equip, and know that all the tube amps run on DC bc AC is just not an option for power tubes... so you have a Hi side/low side power... I wish I had some of your knowledge on this for just a day. And I would have my buffer/polisher worked out!! Thanks for your advise... I'm still looking for a torquee dc motor, or a 110 would be fine I suppose.. It's the shaft that I need to be at least 5" long... I was given the 'BRAND NEW 51-104358-00 x13 that is complete unit from a friend that runs a Hvac warehouse... 220 is not an option unfortunately.. thanks👍🏻

[@bobby_greene]

How could you make this video without actually showing which way it should spin?

[@grayfurnaceman]

That video definitely needs a redo. It was done early in my youtube experience. A new one will be coming. GFM

[@hg2.]

Not exactly "intuitive". Have to take at face value. Maybe "an airplane wing in reverse"? I.e. the wing uses moving air to make low pressure. The wheel uses low pressure to move air. "

[@grayfurnaceman]

You are correct. GFM