Slightly OT: air cleaner fan/blower pressure drop

[Keith Carlson]

This may sound like an obvious question to some of you, but if a furnace-type blower is overly restricted, so has a higher pressure drop than it is designed for, what would you expect to happen to the blower motor? Eventually fail from over-heating?

Just finishing up a shop-built air cleaner/outfeed table/downdraft table (based on a design by charlie b - thanks), and with it running on low, my manometer readings show almost twice the pressure drop that a typical furnace is designed for.

I'm pretty sure the blower is over-sized for this application. Even on low speed, it moves a lot of air. But there's no reason to change it now; it works. I'll use it unless and until the motor does fail.

Just curious whether I might expect it to run for a long time. Or....... expect to see smoke coming out of it anytime.

Thanks

[bluemax1811-newsgroups]

A centrifugal type pump blower/compressor (as opposed to positive displacement) uses less horsepower as you restrict air flow. As an example, a dust collector uses the least amount of horsepower when you block it completely. Cooling the motor does not depend on whether air is flowing through the blower.

Think of it as your particular blower is "loafing".

Bob

[Greg O]

Depends on how much the air flow is reduced. If you are still moving a fair amount of air you probably will be ok. I would run it and get a feel of how hot is gets. A typical furnace blower trying to move restricted air will over amp, and over heat. How long will it run? It is any body's guess. Greg

[Keith Carlson]

Hmm... if it's just "loafing", that would be great. On the low speed, I measured 2.4 amps current draw. Not sure what is typical for something like a 1400cfm furnace blower, but that doesn't sound too bad.

Definitely will be running it. No reason to actually do anything about it unless it does break, and then it would probably be replaced by a lower-cfm unit if I can scrounge one.

[dwright]

If the unit is an "air over" design (motor is inside the airflow) it might overheat from lack of air movement. Blowers that place the motor outside of the airflow don't have this problem - but then their motors have to have better heat dissipation in the first place so they are typically more expensive.