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I currently have a Gentran 3028 subpanel connected to a 12,000 watt generator over a 30 AMP branch and the utility/main panel over a 60 AMP branch. I want to replace the Gentran with a APC UTS10BI. I would like to mount the APC more than the recommended one foot distance away from the utility/main panel. The APC can use a UPS as an alternate power source until I can get the generator running. This is also the reason I need to mount the APC away from the utility/main panel. There isn't enough floor space for a rack mounted UPS system near the main panel. My question is how much of a gauge drop do I need to make to cover the 18 to 20 foot distance? The installation manual recommends a utility line of "Circuit: 12 AWG Two Neutral:10 AWG". If I drop the circuit to 10 AWG and the two neutral to 8 AWG would that be safe?

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There's a lot of different max. amperages going on there. Do you know the actual max. amps through this particular line? Also, sure it's not 2-#12 with 1-#10 neutral? I don't get the over sized neutral, much less two of them. So... anyone know why the over sized neutral? –  bcworkz Feb 2 '13 at 21:04
    
Is the one foot distance a recommendation, or a requirement in the manufacturers documentation? –  Tester101 Feb 2 '13 at 22:06
    
@bcworkz It's not a single #12, it's a #12 per circuit. It's a 8 circuit transfer switch, so it would be 16 #12 ungrounded (hot) conductors and 2 #10 grounded (neutral) conductors. –  Tester101 Jun 6 '13 at 14:25
    
Is this for a home or a data center? –  BMitch Jun 6 '13 at 14:29
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1 Answer 1

According to the Manufacturers Installation Guide (PDF)...

Physical - install the UTS within one foot of the building circuit breaker panel

Page 4

Caution: The UTS must be installed within one foot of the building circuit breaker panel. If the UTS must be located further than one foot from the circuit breaker panel, a licensed electrician must extend the wiring using standard electrical wiring conduit and junction boxes.

Page 7

According to National Electrical Code (NEC)...

National Electrical Code 2011

ARTICLE 110 Requirements for Electrical Installations

110.3 Examination, Identification, Installation, and Use of Equipment.
(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

I'm guessing the unit has permanently attached wires in a raceway, which is of a limited length. So mounting the unit further from the panel would require you to extend these wires and raceway, which requires knowledge of wiring methods to do properly. It's not likely you'll have to upsize the wires, but you will have to understand basic wiring methods (Chapter 1-4 of NEC).

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