I'm getting ready to do a complete boiler re-pipe and tie in a wood boiler. My current domestic water is heated by an indirect. I acquired an 80 gallon AO smith electric water heater that I intend to temporarily install while I resume the project.

I assumed the water heater was 3 wire 208v and required 10/3 & a 30A breaker. The heater didn't come with instructions and I cannot find them online. I pulled the wiring cover off and discovered red & black 12ga. wire, a ground lug & no neutral. 120v comes to mind. Am I correct?

 

Most water heater are 240 volt wired with two hots and a ground on a 30 amp breaker.

Just use the black and red in your cable and cap the white.

 

Can't I still wire it to 120v? It will only take longer to heat & recover? Only reason is I have a 120v/20A dedicated circuit right next to it's temporary location and I would love to splice an extension cord for the time being....rather than running the 10/3 wire and adding the 30A breaker to my panel.

 

It will take 4 times as long to heat the water.

Do not use an extension cord to feed the WH.

 

If you could find an extension cord that would handle the load, that cord plus the special receptacle would probably cost as much as the water heater. And how would you connect it at the heater anyway?

You don't need 10-3/G, just 10-2/G. Plus a 240V 30A breaker:Temporary wiring must meet every applicable section of your locally adopted code, plus some more just because it's temporary.

Electricity is an equal opportunity killer. Wire everything as safely as you can.

 

Not going to risk it.... 10/3 & a 30A breaker will be installed.

 

OK, but what are you planning to connect the neutral wire to?