The water heater that came with my home when I purchased it is on a double pole 30A breaker and wired with 12/2 romex. The breaker seems to be sized correctly for the wattage (4500W) but should it be using 10/2 wire?

I am in Canada so would be following the CEC. Here is the label on the water heater: Water heater label

Also, is this an acceptable way to secure the wire running down to the water heater? enter image description here

  • Cant really offer much , but in Australia , we cannot run that cable like that , the cable must have some sort of mechanical protection ,much like that metal spiral armor sheath with red zip ties on your ventilation system. Dec 10, 2020 at 0:10
  • Would that cable be considered "accessible", or is it way up high out of reach?
    – Nate S.
    Dec 10, 2020 at 0:35
  • Yes, the wire enters the water heater about 5' from the floor.
    – bzeghers
    Dec 10, 2020 at 1:16
  • Noting the armored cable for the furnace in the background, I'd guess that the water heater cable is not up to code.
    – FreeMan
    Dec 10, 2020 at 14:00

2 Answers 2


Make sure you wait for someone with CEC knowledge. It seems some provinces include water heaters as heating equipment and apply CEC 62-114(6) and (7), which I think eliminates the 125% continuous load requirement for the wire if the wire is at least 80% of breaker. So 18.75A in a residential application would allow 20A wire, maximum breaker of 25A.

In the US the Installation Instructions are part of NRTL Listing, which override the NEC. The Installation Instructions from WHI (Rheem) say 25A breaker and #10, so we would have to use #10.

  • My 2015 CEC says that water heaters are indeed covered under the 62-114 rules thanks to rule 62-404. Dec 10, 2020 at 4:21

12ga wire is too small for a 30A breaker, so yes, it must be 10ga. That wiring method is also illegal, it must be in conduit.

  • Citation needed about needing conduit for a water heater connection -- where I live, I don't believe that's true. Though you're right that that particular install of NM cable is a bit questionable, and the wire is definitely too small, so +1 anyway.
    – Nate S.
    Dec 10, 2020 at 0:33
  • The 12g wire is definitely too small for a 30A breaker but I'm not clear that it's too small for a 240V 4500W load. That only comes out to be 18.75A. I'm not any NEC code expert and I'm sure the wire size depends on some other factors. But it's not clearly unsafe other than the improperly sized breaker. A 20A would be safe.
    – jwh20
    Dec 10, 2020 at 1:20
  • 1
    I'm also unclear where the conduit is required. This method of installation may have been code compliant when it was installed.
    – jwh20
    Dec 10, 2020 at 1:21
  • 1
    @jwh20 NEC 422.15 says storage water heaters are to be considered "continuous load", so branch circuit rated at 125%. Dec 10, 2020 at 2:56
  • I know of no time when any code allowed the use of NM cable in a manner that is not protected from damage. Flex conduit / armored cable, fine, but raw NM strung through the air and strapped to a water pipe is never allowable like this.
    – JRaef
    Dec 10, 2020 at 22:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.