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#79965 - 02/10/02 09:32 PM Overkill?
NoShorts4Me Offline

Registered: 01/14/02
Posts: 35
Loc: southern california
I'd appreciate some feed back on this.
Friend of mine owns a custom racemotor shop.He recently bought what I think he called a "shore-pac" unit. Basically a rolling unit with a 480v 3-phase motor ( 8 amps) which drives a large fan for ventilation, for use when welding certain metals. (some osha requirement). The unit would need to be rolled around the shop close to wherever the welding was done.The 480v service panel is located in his shop, but you must exit is shop and walk around the other side of the building for access.All he wanted was advice as to what to suggest to or expect from the E.C. he hired.
My suggestions off the top of my head was..
-3/4" emt (approx.75') w/3- #10's+ grounding conductor on a 15 amp breaker.

- a 30 amp fusible disconnect with integral twistlock plug where the plug can not be removed with out de-energizing the load side of the disconnect. ( I believe Hubbel makes these...."circuit-locks" ??)

-50' of 8-3 w/g cord with the proper Pin/Sleeve connectors ( not sold on this with 480, but I couldnt come up with a safer way considering the mobility need)

- strain reliefs on the cord at the disconnect location and "shore-pac", to hold the cord secure.

Now, what WAS installed a week later ( by a NATIONAL known electrical contractor) ..

- 75' of 1/2" emt with 3-# 12's ( no ground)
- a 480v twistlock plug ( not pin/sleeve) in a 5-square box with raised cover.


Was I way of base with this? (overkill) ???

At the very LEAST a disconnect.
Sorry for being so long winded.


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#79966 - 02/11/02 04:41 AM Re: Overkill?
Redsy Offline

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
A few thoughts--
Does the unit have a starter or combination starter on it? Although the plug may qualify as a disconnect for the motor, a switch would be nice. In an emergency, I would not want to unplug it under load.
The 3 #12s don't seem to be a problem, but at 480 volts, an EGC would certainly provide a much safer installation.
Also, depending on the size of the shop, more than one receptacle would be nice. This would minimize cord length, and the likelihood of it being damaged.

#79967 - 02/11/02 11:42 AM Re: Overkill?
bob3232 Offline
Junior Member

Registered: 02/10/02
Posts: 4
It sounds like this is a 5 hp motor.If it is you have to size the conductor for about 9.5 or 10 amps.With motors you can use the amperage from table 310-16 A #12thhn is good for 30 amps.


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