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Re: hp -> Watts?

To: shop-talk@autox.team.net
Subject: Re: hp -> Watts?
From: <jblair1948@cox.net>
Date: Wed, 2 Jun 2004 14:07:26 -0400
> Our power went out last night, so I ran an extension cord from the little 
> 1000W Honda (EX, not an EU) generator off down to the sump pump, plugged 
> it in, and was dismayed to see the pump not work.  Later on, power came 
> back on and the pump worked fine.
> 
> I can't imagine that pump is anything more than a 1 hp unit, probably more 
> like 1/3 or 1/2 hp...  What size generator do I need to make that puppy 
> work?

Mark,

That depends on the pump.  But the conversion for HP to
Watts is 1hp = 750Watts.  Now for example, a 5hp compressor

5hp = 750watts * 5 = 3750Watts or 3.7 KiloWatts (KW).
For a 110Volt AC line (also called 115 or 120) the current
would be P=IE (Power[P] = Current[I] * Voltage[E])
3750 = I * 110 or I = 3750/110 = 34.1 A with NO safety 
factor.  The max for a typical household 110 circuit is 20A.
So you can see that for a 5HP motor, you would need 220V
service.

So to answer your question, you need to find the data
plate on the motor for the pump, and find out how much
current it draws, and at what voltage.

Again Power[watts] = Current[Amps] * Voltage[volts].
So now you can figure out how much power the pump needs.
If the pump is 220 V and the generator is only 110 then
the pump won't work.

Hope this helps


John






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