Paralleling 8-gauge wires to a 220V Subpanel for Tankless Water Heater

edwardtx · Aug 4, 2022

Hello,

Question is regarding a recently purchased property in Central Texas, which includes a 27KW tankless electric water heater. It is four years old and working fine.

What the prior owner installed is surely not code compliant, but the county does not require permitting for "renovations made within the original square footage of buildings".

The subpanel breakers next to the water heater are essentially nearby cutoff switches. The main panel is 80 feet away.

Aside from the code, is there anything electrically wrong with this setup that it would make good sense to (1) replace the wiring to subpanel or (2) remove the subpanel completely?

[ElectriciansForums.net] Paralleling 8-gauge wires to a 220V Subpanel for Tankless Water Heater

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James · Aug 4, 2022

I would be looking at removing the sub panel, it looks to be reducing safety rather than improving it.
have you spoken to any local electricians?

edwardtx · Aug 5, 2022

James said:
I would be looking at removing the sub panel, it looks to be reducing safety rather than improving it.
have you spoken to any local electricians?

Thanks. I spoke with a couple of experienced electricians in a large electronics manufacturing plant I work at. Neither saw anything "wrong" per se with the setup from a purely electrical circuit point of view. Just looking to see if anyone has a solid argument beyond "doesn't look right"

James · Aug 5, 2022

The thing wrong is someone could expect that turning off one of the outgoing breakers in the main panel would make the outgoing terminals dead, in this case they would remain live.

in the U.K. if you are running cables in parallel then they need to be fed from the same circuit breaker. (Amongst other requirements)

Megawatt · Aug 10, 2022

B

edwardtx said:
Hello,

Question is regarding a recently purchased property in Central Texas, which includes a 27KW tankless electric water heater. It is four years old and working fine.

What the prior owner installed is surely not code compliant, but the county does not require permitting for "renovations made within the original square footage of buildings".

The subpanel breakers next to the water heater are essentially nearby cutoff switches. The main panel is 80 feet away.

Aside from the code, is there anything electrically wrong with this setup that it would make good sense to (1) replace the wiring to subpanel or (2) remove the subpanel completely?

View attachment 100096
t

By Code you are not allowed to parallel nothing under 1/0 wire, and that’s a big tankless water heater. You wire size needs to be # 3 at a minimum. My mission is to tell you the correct answer to your question by code. You live where you live and if code enforcement doesn’t care then all I can say is good luck with your project