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#12 to water heater

4K views 18 replies 10 participants last post by  oldtimer 
#1 ·
On a service call today to hook up a new electric water heater (they replaced their old one because it stopped working) I found #12 feeding it connected to a 60 amp breaker. The #12 had actually burned into at the connection. I replaced it with #10 on a 30. Amazing what some people will do to save a few bucks instead of calling an electrician to begin with! I advised they get smoke detectors...
Just had to share it.
 
#3 ·
I believe it was code compliant, years ago , to wire the water heaters with #12 but not use a 60 amp breaker. :)

4500 watts divided by 240 is 18.75 amps. Most water heaters don't take but 30 to 45 minutes to heat the tanks but the code does state we must consider it a continuous load-- I just don't know why. #12 will work just fine.
 
#12 ·
I was reading 422.11 E2....I assumed that would apply to a water heater if the max fuse size wasn't marked on the unit. Isn't #12 thhn good for 25 amps on the 75 degree column?
In some instance you can use #12 at 25 amps but not in general. Read art. 240.4(D)(5).

The exception for using 25 amps would be with anything listed in T.240.4(G) -- mostly motors and a/c units is where most of us get to use it.

You are correct that 90C or 30 amps can be used for derating but the end use of #12 would be limited to 20 amp OCPD.

Notice the asterisk in T. 310.16 next to #10, 12 & 14 wire. The note takes us to 240.4(D)

For a water heater #12 is limited to 20 amps
 
#14 ·
In the days before all water heaters were "quick recovery", most electric water heaters were fed with #12.
 
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