# Thread: Understanding pump "Service Factor"

1. ## Understanding pump "Service Factor"

What exactly is "service factor"?

http://www.electricmotorwarehouse.com/pool_pumps.htm

Comparing the standard pumps to the high efficiency pumps, the high efficiency have higher service factors. But they seem to use more amps, which is confusing me, but my understanding of amps/volts etc left me long ago

I assume a higher service factor is desireable?

2. No, service factor (SF) in and of it's self doesn't matter.

There are several different definitions of HP. You multiply the listed HP by the SF to get the brake horsepower, which is what actually gets applied to the water. It's all a morass of different standards and deciptive marketing. See WikiPedia for some background. Some manufacturers sell motors of various HP that are actually all the same motor, just with different SF.

What you really want to compare is amps vs GPM at the dynamic head you expect to be running at.

3. Thanks.

Originally Posted by JasonLion
What you really want to compare is amps vs GPM at the dynamic head you expect to be running at.
And I assume the lower the amps for the same GPM at the same dynamic head, the less energy used and more efficient the pump?

4. Right, low amps are good, high GPM are good.

5. 'Service factor' is a number that pump manufacuters use to inflate the HP of a particular pump. The brake HP is the important number. For example I will use 2 Pentair Whisperflo pumps, a full rated 1 HP and an uprated 1.5 HP. First, these are EXACTLY THE SAME PUMP WITH THE SAME MOTER, IMPELLER, VOLUTE, etc. and pump EXACTLY THE SAME AMOUNT OF WATER! The only difference is the nameplate and the price! In the 1 HP full rated pump there is a service factor of 1.65. You multiply the service factor by the rated HP to get the brake HP, in this case it's 1.65. Now the upratred 1.5 HP pump. This one has a service factor of 1.1 so you multiply this service factor by the rated HP of 1.5 and you get a brake HP of 1.65!
I picked on Pentair but all major pump manufacurers play this game. Some pump model lines are only uprated, btw (Pentair Pinnicle for example). When buying a pump you want to look at the brake HP and the pump performance curve to see what size pump you need. Also, check prices. Sometimes the equivalent uprated pump is less expensive than the full rated lower HP model in the same product line even though they are exactly the same pump.

High efficiency pumps use a different motor and save about 10% in electricity costs over a standard pump of the same model and HP. They also come in uprated and full rated models in many product lines.

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