# #12 to water heater



## TOOL_5150 (Aug 27, 2007)

Xknob&Tube said:


> 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.


In colorado huh? maybe they were trying to keep warm with that circuit. :laughing:

~Matt


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## Dennis Alwon (May 9, 2009)

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.


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## Electric Al (Mar 13, 2010)

We usually use #12 for 3000 watt and 20 amp breaker OR #10 for 4500 watt and 30 amp breaker. 240 volt.


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## Dennis Alwon (May 9, 2009)

Electric Al said:


> We usually use #12 for 3000 watt and 20 amp breaker OR #10 for 4500 watt and 30 amp breaker. 240 volt.


That would also be appropriate for Nec rules.


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## Xknob&Tube (Jul 30, 2008)

Dennis Alwon said:


> 4500 watts divided by 240 is 18.75 amps


Since 310.16 says #12 THHN is good for 30 amps, I figured the connection had been loose since that is where it burned into.
http://www.houwire.com/products/technical/article310_16.html


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## NolaTigaBait (Oct 19, 2008)

It's good for 25 amps, you derate from 30 amps.


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## Dennis Alwon (May 9, 2009)

NolaTigaBait said:


> It's good for 25 amps, you derate from 30 amps.


Well it could only be good for 20 amps depending on the application.


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## NolaTigaBait (Oct 19, 2008)

Dennis Alwon said:


> Well it could only be good for 20 amps depending on the application.


True, if it's under 13.3 amps....


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## Dennis Alwon (May 9, 2009)

NolaTigaBait said:


> True, if it's under 13.3 amps....


Nola I am confused by your posts. What does 13.3 amps have to do with anything? And please explain the 25 amps on #12.


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## NolaTigaBait (Oct 19, 2008)

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?

Is #12 limited to 20 amps on a water heater circuit?..I guess it is...


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## Dennis Alwon (May 9, 2009)

NolaTigaBait said:


> 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


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## NolaTigaBait (Oct 19, 2008)

I assumed that water heater fell under that exception...guess I was wrong(not that I have ever used #12 fora 4500w water heater) even though theres probaly never going to be a problem with #12


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## MDShunk (Jan 7, 2007)

In the days before all water heaters were "quick recovery", most electric water heaters were fed with #12.


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## jwjrw (Jan 14, 2010)

Dennis Alwon said:


> 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.


 

Yep see #12 on old water heaters everyday here. I like to see it because I get to pull another circuit and set a disconnect which is usually not there also.


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## nikolongdong (Jun 8, 2010)

*wire size*

as mr wielden would say you can refere to page 310.16 in your nec books


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## Dennis Alwon (May 9, 2009)

nikolongdong said:


> as mr wielden would say you can refere to page 310.16 in your nec books


Mr. Wielden knows nada about the NEC..


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## Shockdoc (Mar 4, 2010)

I'm a cheap bastard, I wired my own 40 gal tank w/ #12.......It works fine. My customers however would get #10.


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## oldtimer (Jun 10, 2010)

Shockdoc said:


> I'm a cheap bastard, I wired my own 40 gal tank w/ #12.......It works fine. My customers however would get #10.



The capacity of the tank does not determine the size of the feed. The wattage of the element does! E.G. 3000 watt # 12 .... 4500 watt # 10. (It's in the book) as prof. Irwin Corey would say !!! :laughing:


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