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?
Electrical – How to install this automatic transfer switch
electricalgeneratorswitch
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That does indeed describe a properly engineered 50 amp device.
It is normal for appliances to use slightly lighter gauge wire than would be used in building wiring. You can observe that inside electric ranges, dryers, and water heaters, where you will see the 10 or 8 gauge incoming supply wires to a terminal and then 12 or 14 gauge wire going from the terminal block off to the components.
Because the wire is inside an enclosed box, and is not tightly bundled or surrounded by thermal insulating materials, its elevated temperature will not cause any danger. It will run a little warm at peak current, but be far below "hot". The same is not acceptable inside dwelling walls were it will be in contact with wood, fiberglass, cellulose insulation, etc.
As for standards, I have determined this is beyond the scope of the NEC and falls into the domain of the National Fire Protection Association (NFPA) standards. That seems to cost $$ to view.
You could simply pull a properly sized cable from the transfer switch, out to the garage. Then install a generator input receptacle in the garage.
There's likely a knockout in the bottom of the transfer switch to allow for this. If not, you may be able to add your own (check with the manufacturer).
Moving the transfer switch, and migrating circuits is is likely going to be a huge headache. It's much simpler to pull a single new cable.
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Best Answer
According to the Manufacturers Installation Guide (PDF)...
Page 4
Page 7
According to National Electrical Code (NEC)...
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).