one circuit or two? - Electrician Talk - Professional Electrical Contractors Forum

goose134 · 09-23-2011, 08:51 AM

I don't do a lot of motor work, so forgive me if this is a 101 question. I have a setup that has two pump motors that will be used alternately through the use of a sequencer. The loads are small (3 A@ 480 v)) and will be protected by individual overload protection. Can I power the two motors with one circuit or do I need a circuit for each?

HARRY304E · 09-23-2011, 08:57 AM

Quote:

Originally Posted by goose134

I don't do a lot of motor work, so forgive me if this is a 101 question. I have a setup that has two pump motors that will be used alternately through the use of a sequencer. The loads are small (3 A@ 480 v)) and will be protected by individual overload protection. Can I power the two motors with one circuit or do I need a circuit for each?

You only need one circuit because they are only 3 amps and they will not be running at the same time.

And even if they were that's only a 6 Amp load.

Jlarson · 09-23-2011, 09:15 AM

I don't see anything there that would make it so you couldn't put both on the same branch circuit.

Although If its a critical app putting them on one circuit could come back to bite of one motor shorts and trips the breaker.

alpha3236 · 09-23-2011, 09:18 AM

Perfectly legal, size the wire at 125% of the largest motor plus the other motor. Do it all the time.

goose134 · 09-23-2011, 01:53 PM

Good point about the critical load. I think in a different case I'd put them on seperate circuits just for a bit more certainty. This is pumps for a air conditioning setup. I didn't think it would be a problem, but I wanted to find out from guys who knew much more than me. Thanks again.

BBQ · 09-23-2011, 01:55 PM

220.60 Noncoincident Loads. Where it is unlikely that
two or more noncoincident loads will be in use simultaneously,
it shall be permissible to use only the largest
load(s) that will be used at one time for calculating the total
load of a feeder or service.

oliquir · 09-23-2011, 02:27 PM

Quote:

Originally Posted by alpha3236

Perfectly legal, size the wire at 125% of the largest motor plus the other motor. Do it all the time.

that rule is ok but don't use smaller than 14 awg

you can even use only one overload protection for the 2 motors if the contactors for the 2 motors are interlocked (similar to a reversible contactor) since only one will run

goose134 · 09-23-2011, 06:37 PM

Bob brings up an interesting point. I'm not 100% sure of the circuit logic, but I think it's designed to run the pumps as alternates. I do know that the sequencer allows for an operation that would ramp one down while running the other up. Now I'm pulling#10 THHN but if the logic is set in the way I just described, would it be a violation?