Motor Starter & Disconnect

horsegoer

Senior Member
Location
NJ
Two questions regarding this FWP-2-5( deaerator for boiler).
  1. Panel schedule calls for it to be fed with 3#12’s but they are using a 3P/60A disconnect switch. Disconnect switch incorrectly sized IMO.
  2. Mechanical schedule calls for the equipment to come with DOL starter furnished by mechanical. Some starters can me a combo starter/disconnect. Do you think the disconnect shown on the electrical is a separate loose disco or the disco is part of the starter? Or could the starter just have overloads and still have a separate disconnect provided by electrical?


Thanks.
 

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augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I would think the disconnect shown would be the 430.102 "in sight from"disconnect.
The #12 conductors would make sense for a 10HP 480v motors.
A 60 amp disconnect would not be required (30 amp would work) but would be allowable.
 

DrSparks

Senior Member
Location
Madison, WI, USA
I would think the disconnect shown would be the 430.102 "in sight from"disconnect.
The #12 conductors would make sense for a 10HP 480v motors.
A 60 amp disconnect would not be required (30 amp would work) but would be allowable.
Disconnects for motors go by horsepower for interrupting capacity. You would need one rated for more than 10hp. So that might have bumped it up to a 60.

I would simply connect with the GC or architect/ engineer for clarification. Would hate to see you guess wrong and have to go back and fix it!

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Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I would think the disconnect shown would be the 430.102 "in sight from" disconnect.
The #12 conductors would make sense for a 10HP 480v motors.
A 60 amp disconnect would not be required (30 amp would work) but would be allowable.
I agree. I've not seen a 30A disconnect that is not rated for at least 10HP. In fact most 30A disconnects are rated for 20HP @460V.
60A does seem like overkill, but maybe they want "room to grow"? If they are willing to pay for it, why waste time arguing?
 

DrSparks

Senior Member
Location
Madison, WI, USA
I agree. I've not seen a 30A disconnect that is not rated for at least 10HP. In fact most 30A disconnects are rated for 20HP @460V.
60A does seem like overkill, but maybe they want "room to grow"? If they are willing to pay for it, why waste time arguing?
Yeah some engineers like to overbuild. But yeah, I mean they're paying for it why argue?

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horsegoer

Senior Member
Location
NJ
Ok, thank you. But what about the DOL(starter) being a separate piece of equipment form the disconnect or is the disconnect switch shown the starter indicated on the mech schedule?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
It appears that the disconnect shown at the motor is simply a motor disconnect. The DOL would be a seperate piece of equipment.
 
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