I purchased a Reliance Q510-C transfer switch to use with a 50 amp generator at my house. The transfer switch is rated at 50 amps. I have wired it into my main electrical box.
I also wired a 50-amp power inlet box into the transfer switch so I can plug the generator into that (rather than run the cord into the house). I used 6 gauge wire to connect the inlet box to the transfer switch.
The transfer switch and the inlet box are both rated at 50 amps. Everything is installed and works fine.
There's just one thing that bothers me. The transfer switch has a terminal block to connect the inlet wires. So the four wires coming into it (from the inlet box) are 6 awg wire. Two hot wires, one neutral and one ground. The four wires coming out of the terminal block are 10 awg wire. So it goes from 6 awg to 10 awg at the terminal block. Red 6 goes to red 10, black 6 goes to black 10, etc.
Here is my question…
Why would the manufacture use 10 awg at the terminal block? I expected the wires to be 6 awg (the same size coming from the generator power inlet). The 10 awg wires are only about 8 inches long and they run into the main bar where all the breakers connect. I assume the manufacture knows what they are doing and that 10 awg will carry the load, but I have never seen 10 awg used in 50 amp applications.
Is this OK, should I call and ask the manufacture if they made a mistake (they sell 30 amp boxes exactly like this… maybe this is a 30 amp box mislabeled as a 50 amp box) or should I not worry about it and just use the box as is?
The neutral wire they use at the terminal block is 8 awg. The others are 10 awg. I'm really only concerned about the two hot wires (red and black) that go from 6 awg to 10 awg at the terminal bolck.
Best Answer
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.