Is 40 amp Breaker Included with ETBC7 Sufficient for Use with 10 Gauge Wire

Question:

I am about to install the ETBC7 on my 2006 Toyota Sienna Limited, and I see from the instructions that the run of grey duplex wire to the rear of the vehicle gets installed with a 40amp breaker. The included grey duplex wire looks like 12 gauge, or maybe 10 gauge at most, so would 40 amps be far too much current for it to travel the 10-15foot to the rear of the vehicle. A web page I saw shows I would need about 6 gauge to support this, so Im wondering if this is a fire hazard. From that chart it looks like it should have a breaker of no more than 20 amps. Thanks!

asked by: Adrian H

Expert Reply:

The duplex cable included with the ETBC7 kit uses 10 gauge wire, which is appropriate for handling a circuit with a maximum of 40 amps with a run of 25 feet or less.

We sell thousands of these kits per year, and have never had a reported problem with the gauge of wire being insufficient. Keep in mind that the primary purpose of this circuit is to maintain (not charge) a trailer mounted battery or to power a trailer mounted accessory requiring limited amperage, such as interior lighting. Trailer mounted accessories like a winch that have greater power requirements would certainly need a larger gauge wire and would be connected using a separate wiring harness. As long as this accessory circuit is used in the purpose it was designed for, 10 gauge wire protected with the 40 amp breaker works just fine.

You could certainly go with a lower amperage breaker if you care to, but the capacity of the circuit would be decreased.

expert reply by: Mike L