3 phase disconnect - correct size rating

[utimgr]

In the midst of a discussion with another PM about this....

System is 3 phase, 480VAC, total HP of motors are 28.166 (25,2,.5, 1/3, 1/3) and 42.3FLC (36,3.5,1.2,.8,.8)

I'm saying that we need a disconnect rated at min of 30HP or 45A....he says its 1/3 of that since each phase carries 1/3 of the FLC. Say it enough times and it starts to make sense..but still doesnt sound right. Each leg is out of phase, but still carries the FLC ?

 

[dpc]

Each phase carries the full load amps.

 

[waross]

dpc said it all. You can't say it enough times for it to make sense.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

He must be a politician. Repeat a lie enough times and someone will believe it.

And by the way, 480V and HP ratings implies North America, subject to the NEC or CEC, both of which have specific code requirements for mimum sizing of disconnects for multiple motor loads. I suggest you read them before moving forward, any other course of action is irrelevant until after that minimum is met.


"Will work for salami"