does a 1HP 120VAC/1ph motor need a starter for an industrial application?

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emiller233

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pittsburgh, pa
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Controls-Automation engineer
For a 1HP 120VAC/1ph motor for an industrial application
Does it need a starter(fuse, contactor, and overload relay), or can we get away with just using a fuse and a switch rated for the motors amperage to start/stop it?

its running a small hydraulic pump on a test bench
 
Typical 1 phase motor has built in thermal (running overload) protection, so you do not need to add it, in a starter, if yours does. You also need the short circuit protection which for a motor load is a time delay fuse at 150% to 175% of fla or thermal magnetic breaker at 250% of fla. That's the old code rules. Current code you have to use the motor hp rating and then the table values, but the result should be similar.

Short circuit protection is not sized right at fla for a motor load.

Switch has to be hp rated.
 
I've never dealt with single phase motors before obviously, so I appreciate the guidance! I am still unsure of everything after reading that article. Everything im looking up is generally dealing with 220vac single phase motors, not 120vac..

The motor will not be automatically started, manually with a disconnect switch, mentioned below

I'm assuming the motor will have the integral thermal protection that you mention , as it will be a Rexroth motor (don't know exact model # yet) .
I shouldn't have to follow 430.32 according to that article article it is 1hp or less.

I was looking at using a fused (class J - time delay) disconnect switch with a thru door handle to turn the motor on/off. It's 30A max, but I'd fuse it at your recommended 150-175%, whatever that is...
That would give me short circuit and overload protection(even tho not required at 1HP) with provision for a Lock Out Tag Out locally right at the motor. Am I wrong here?

Eaton # R9C3030U
It is HP rated but not for a 120Vac motor...?
(Page 17)
http://www.eaton.com/ecm/idcplg?Idc...veAs=0&Rendition=Primary&dDocName=PG00802002E

Would it be better practice to use a non fused disconnect switch and a single pole circuit breaker such as Eaton faz-d20/1-na-sp (assuming 20A is 150% of the motors FLA)
https://www.google.com/url?sa=t&sou...FjADegQIChAB&usg=AOvVaw2DM0VdfrFzoqPAJqnjQQvR



There will also be another control circuit inside this enclosure if there's any relevance to a good design here. It's just a 120vac solenoid that I will put a single pole CB with a selector switch to control it
 
I think you’re over analyzing it. If the motor has integral overload protection, simply use a HP rated switch and you’re good to go. The fuses only need to protect the branch circuit conductors.
 
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