How the squirrel cage blower works

This one describes how these blower wheels are put together, their rotation and what they are capable of.

[@RedeyeRaccoon]

Thank you for the vid. My fan was rotating the wrong way and I needed reassurance. I found it here! I've got air! Thank you again!

[@jediclint]

Having watched a few of your HVAC instructional videos, I would like to thank you for not only presenting relevant and important information but also for the way in which you present that information. I think you are a very competent technician and an excellent instructor. Again, Thank you. Sincerely.

[@grayfurnaceman]

Welcome, Merry Christmas GFM

[@rj.parker]

Actually a squirrel cage blow can be made with forward curved, backward curved or straight (radial) blades. Each has its advantage and each will have the same direction of air flow. But an ac front curved version is quieter, has good static pressure handling but exhibits relatively lower cfm than a backward curved version. A radial blade will have reduced particle buildup and is often used for vacuum cleaners. The ac front curved blade does buildup particles so it must be used with good filters in a relatively clean air application. The blower housing is a key component of a squirrel cage (centrifugal) assembly as it limits the direction the air can go, provides pressure buildup needed to overcome ductwork restrictions and directs the flow to its outlet. Unlike a propeller blade, a squirrel cage motor and wheel is useless without its housing. Another interesting discussion is how an ecm motor can sense airflow and adjust output without any direct pressure or airflow sensors.

[@rj.parker]

@Shep VanDelay A refrigeration textbook like "Modern Refrigeration and Air Conditioning" Althouse

[@InspiredScience]

@Shep VanDelay - Those are amazing projects. I'm curious how you've modified a window unit to run as your 5th-wheel RV AC unit. Can you explain in more detail? Also, if you are interested, I have the book mentioned above and can upload it for you, if you like.

[@rdymond1]

Fantastic. After installing a new blower motor and testing it, air started coming out of the cage backwards into the duct. I assumed the direction was incorrect. Then the limit switches kept shutting off the furnace because it was getting way too hot. After watching your video I undid my direction change so from the motor side the cage is spinning counterclockwise. Air was spilling out all over as I ran another test, and it works! Driving far more air now, the furnace isn't overheating and the new blower motor is quiet and powerful.

[@kj7ym]

Finally! As soon as you mentioned the blades air an airfoil, it all fell into place. The same pressure difference that lifts a plane into the air.

[@grayfurnaceman]

You got it. GFM

[@chuckswenson8044]

Thanks your video helped me solve my problem,my fan was running backwards, looking at the stupid thing it jus doesn’t make sense, but I reversed it and it works fine now,thanks again

[@mitchdenner9743]

Makes sense, leading edge of the blade toward rotation scooping air and throwing it towards the discharge all while creating negative pressure on the back side of the blade to pull more air in to take the place of the discharged air. Positive to negative, like hot to cold.

[@aideniridescence1437]

That's what I took from it. they're like spoons or just curl your palm, then throw. They're like a bunch of curled, scooped hands throwing air at that direction.

[@jesseamc6548]

Great content as always! Thank you for the videos and knowledge to keep us techs sharp in the field.

[@jaimimcentire99]

it's a centrifugal fan. It spins the air, and then the force of the spin pushes it outward. Like those old carnival rides.

[@kj7ym]

Always teaching about the questions others miss. You Rock man!

[@jimgill5706]

I haven't seen any videos from you in a while but maybe I didn't look hard enough. Thanks for all time and effort that you put in to share your HVAC/R knowledge and experience.

[@grayfurnaceman]

I publish one video per week on Monday at 2:00 PM Pacific time. Sometimes I add one during the week. GFM

[@nodnarb4162]

So glad that I'm not the only person who thinks the blade angle looks backwards. Even with the high power aircraft liquid pumps I used to assemble & bench test, it seemed like the impeller blades were backwards, but they work! ;+)

[@jm219723]

Thanks for posting. I wish you could continue on this subject regarding maintaining a constant pressure across the coil, and what a worn belt or pulley, or broken ductwork might cause in the refrigerant cycle.

[@DavidHemingway]

Thank you so much! I was trying to get the hub off and I just pushed the motor out the back which seems perfect now

[@skerlone]

each blade creates a negative pressure behind it that is puling air from inside the wheel and pushing it to the outside because of centrifugal force. each blade is like a air foil and the force exerted by the blades can move more air by suction behind then by pushing with positive pressure in front of the blade.

[@analogmoz]

It IS sort of hard to explain, so I thank you.

[@hg2.]

Another nuance learned - thank you.

[@sanch068]

Thank you for your knowledge!

[@grayfurnaceman]

Welcome GFM

[@jhh243]

Good explanation! Thank you sir

[@xelaju8]

Great video. I like them a lot.

[@georgetirebiter4343]

Very informative. thank you.

[@rottnlove]

I don't know how the installers were trained or if they had any previous experience at all, but if it could be done wrong, they did it all wrong. I had some problems with the motor and run capacitor which I decided to replace myself. I discovered that the installers used a CCLW motor with a CLW blower fan wheel. The housing shows the rotation to be the same that the motor rotates the fan wheel, but obviously with a CLW fan wheel the blower is not functioning to the capacity that it should be if it were correct. How did the installers manage to get CCLW motor and CLW fan wheel, in a brand new furnace they ordered and installed?

[@chetmyers7041]

Would be fun to see a demonstration of a working SCB running correctly, and backwards. Do it in the case, so you can demonstrate the rate of flow. What happens if it runs backwards? Does it work very poorly, or does it actually move air the wrong way? Hard to believe it could fight against the centrifugal force.

[@twincamspit]

I wired my Smiths heater fan backwards, it still blew air out of the ducts rather than sucking

[@MirAqueelAli]

Nice explanation

[@bigbuddhabelly]

Very interesting, my company does plumbing and heating. I came across a Whalen heating unit and coming from the plumbing side, the fan wheel appeared to be backwards. With water, the blade is curved away from the direction of spin. This cause the fluids to be collapsed into a small area (between the blade and wall of housing) which creates a higher pressure zone. Then, the higher pressure is pushed out into the system, while simultaneously a lower pressure zone is created at the entrance of the pump, which pulls water from the system in. I’m curious as to why engineers have decided to *throw* the air with the forward scoop as compared to with water?

[@grayfurnaceman]

Air and water are quite different. Air is compressible. The wheel acts like a wing. The negative pressure draws the air into the blades. GFM

[@fryncyaryorvjink2140]

So is a squirrel cage a better choice than an impeller, at least for lower rpms?

[@grayfurnaceman]

The squirrel cage blower is used when there is back pressure, as in ductwork. This type of blower will work against fairly high back pressure. The bladed fan will only work in free air. GFM

[@MR_UNOoo]

What's the best way to create back pressure

[@grayfurnaceman]

Back pressure in the HVAC fan is dependent on speed and the design of the fan blade. When reaches its max speed, the back pressure is at its peak. GFM

[@ElzaVizinha]

❤

[@lindamahoney7229]

Squirrel cage fan on Lennox making noise. Can't seem to adjust it to stop noise. Do these wear out or what is the problem?

[@grayfurnaceman]

If the is making a kind of rattling noise, the cage is coming apart. It must be replaced. GFM

[@charlesjefferson2042]

Is the center hub supposed to be stationary?

[@grayfurnaceman]

Yes. If it is loose, the blower must be replaced. GFM

[@brentaudi9354]

Great Subject. Do you remember the Condenser units that had the blower wheels? GE, Westinghouse, Carrier, etc. had them on many Condenser units during the 60s. We had a very large GE unit that had two large wheels in the front that you could see spinning. Both were connected to same motor. The coil was flat in the back of the unit. The heat that was blown out the front was powerful. I think that unit lasted about 40 years in that house and that was Louisiana summers.

[@grayfurnaceman]

I have seen them. They did move a lot of air. They also tended to be noisy. GFM

[@alcaedafiebre]

So it pushes it out like a centrifuge?

[@grayfurnaceman]

To some extent, that is true. GFM

[@1weirddoe571]

Rebalancing or trueing tips?

[@grayfurnaceman]

Replace the wheel. GFM

[@n2daair23]

Where do those little bastards get into these? I actually just had to remove a nest the chipmunks made in my truck!

[@vjjohn7997]

Yeah, oru thengem correct alla

[@ElzaVizinha]

❤