Is 12 AWG ground wire adequate for a 60 Amp water heater circuit

grounding

A tankless water heater I bought arrived with a pig tail with 3 6 AWG wires. Black, Red, and Yellow with Green stripe ground. The black and red go to a 2 pole 60 amp breaker with the yellow/green going to ground/common on a very old Cutler-Hammer breaker box.

I went to the local box store and they didn't have the 3 6 AWG wire but did have a two 6 AWG with a 12 AWG ground. I was told that it would work just fine with the Black 6 AWG, White 6 AWG and 12 AWG ground.

I connected everything and the heater works great. However, I'm concerned that the 12 AWG wire is a huge mistake and it might actually be a fire hazard and I should remove that wire and replace with a 3 6AWG wire.

Should I be concerned or not?

Thanks in advance.

Best Answer

NEC allows safety ground conductors to be smaller than active conductors.

Neutral carries current under normal conditions, however your appliance does not use neutral. Thus, you MUST re-mark both ends of your white wire with black electrical tape to connote that it is a hot wire. This is mandatory; you are no longer allowed to skip this marking "if the usage is obvious".

Neutral is not ground. Ground carries current only under fault conditions, i.e. long enough for the breaker to trip, so it doesn't need to be sized for continuous use.

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