Estimating Electric Motor Heat Production

[bekirk]

Does anyone have a quick calculation method for estimating the heat generated by an electric motor? I'm curious if I can provide sufficient heating from a pump motor to keep a pump house above freezing while the pump is running.

 

[Clyde38]

Watts_loss=I²R

 

[bekirk]

That's concise, but is there an easy way to estimate the resistance for a pump motor?

 

[speco]

Bekirk,

If you have the motor efficiency, it is pretty safe to assume that the rest of the input power is lost to either friction or I^2R losses. Either one comes out in the form of heat.

Say you have a 10 hp motor with a full-load efficiency of 90%, and operating at full load. The heat generated would therefore be the remaining 10%. Converted to heat, that would be 2544 BTU/hr (1.0 Hp).

Regards,

speco

 

[bekirk]

Speco,

Thanks for explaining. That's pretty simple. The complicated question then becomes how much heat is transferred to the water being pumped vs. the air around the pump.

Thanks!

Bekirk

 

[IRstuff]

That depends on who built the coolant system. If the manufacturer did, and it requires water cooling, we use a 90/10 rule, i.e., 90% of the heat goes to the water.

TTFN

FAQ731-376

 

[bekirk]

IRstuff,

As far as I know, the centrifugal pump used in this case was designed to be air-cooled, and that heat transfer to the product being pumped (i.e. water) was intended to be minimized. So I was guessing that in this case heat transfer to water was much less than 90%, but to be honest, I really don't know.

 

[IRstuff]

Sorry, I read your description as if there was a separate water cooling system.

In your case, the heat rejection into the air should be at least 90% of the motor heat load.

TTFN

FAQ731-376

 

[bekirk]

Great! I think in total that pretty much answers my original question enough for what I need it for.

Thanks,

Barton