transfer switch - wire gauge


Old 11-26-11, 06:25 PM
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transfer switch - wire gauge

We're installing a transfer switch (general electric TC10323R) Transfer Switch-TC10323R for a 7000W generator. The specs for the switch say it can accommodate "12 - 1 AWG/kcmil". Does that mean it's supposed to fit from #12 gauge to #1 gauge? The specs also say "Single-phase, 3-wire SN, 100 Amp , 120/240 VAC". That would seem to imply that each lug could take up to 100A (#1 gauge) wires. However, our #2 gauge wires were too big for it and it seems only #4 gauge could fit.

Our breaker box has 2 #2 gauge wires going into the main breaker. The main breaker has 2 breakers tied together and says "150A" on it. I assume this means that each half can take 75A?

We were thinking of using a split bolt connector to splice the #2 gauge from the meter down to a #4 gauge to the transfer switch. Then running the #4 gauge back to the main breaker.

Wondering what the codes might be for this and also if there would be any problems from the insurance companies.

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Old 11-26-11, 08:30 PM
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The specs should be correct. The wire size the lugs fit is #12-#1. Sometimes, it can be challenging to get the wire to fit if all the strands are not straight, your not inserting the wire straight, or you have not backed the lug screw out far enough. The lugs, and switch, is rated for 100 amps.

It is odd that your main is fed with #2 wire (assuming copper) Code requires a minimum of #1 copper for 150 amp. You might have an issue here. You need to fix this or have somebody fix it.

Your breaker is rated at 150 amps. This is not divided between the legs of the service. You may have one leg drawing 150 amps before the main will trip.

You may not under size your wires by splicing a smaller wire so it will fit. Doing so can cause the wire to get too hot and start a fire.

Lastly, Your service is rated at 150 amp but the switch is only rated 100 amp. If you are planing on carrying the entire load of your house, through the transfer switch off the meter, you need to install some 100 amp fuses before the switch. That, or install a larger rated (at least 150 amp) transfer switch. Maybe a more detailed description of your layout is in order. You will need an inspection for this project. Your insurance company will like to see this.
Old 11-26-11, 10:37 PM
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That would seem to imply that each lug could take up to 100A (#1 gauge) wires. However, our #2 gauge wires were too big for it and it seems only #4 gauge could fit.
If you look very closely at the lugs you'll probably find each individual lug is also marked with the range of sizes they will accept. GE doesn't make lugs and probably buys them out from another manufacturer.
Old 11-27-11, 12:30 AM
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Are you sure that your "# 2 gauge" conductors are not in reality 2/0 conductors? Number 2 would be pretty small for a 150 ampere service whereas 2/0 would be the proper size.

Also, as has already been mentioned, you cannot use a 100 ampere transfer switch on a 150 ampere service.

Lastly, the service conductors are always energized so it is necessary to get the utility (or a licensed electrician if allowed in your area) to disconnect the meter in order to install the transfer switch. This job needs to be permitted and inspected.

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