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Old 11-14-2009, 09:12 PM   #1
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Code question, elec. water heaters


A WH is on #14, which is undersized for a 4500w, 240v element.
If the element is changed to 3300w or lesser wattage is there any reason that the 15A breaker feeding the #14 wire cannot stay?
I realize the recovery time will be longer.

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Old 11-14-2009, 09:30 PM   #2
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Code question, elec. water heaters


15a is only good for 1800w
If its 3300w combined between 2 heaters - each 1650w then I'd think so

A 4500w (37.5a) heater actually has 2 heaters = both are 4500w
Only one works at a time
Mine is on a 30a breaker & #10 wire (I think - have to check)
Yup....30a 240v breaker

And that is what was called for in the installation instructions

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Old 11-14-2009, 09:36 PM   #3
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Code question, elec. water heaters


15A is 3600 watts at 240V.
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Old 11-14-2009, 09:40 PM   #4
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Thank you....must be tired

That's why 30a 240v works for mine
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Old 11-14-2009, 09:46 PM   #5
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Originally Posted by Scuba_Dave View Post
Thank you....must be tired

That's why 30a 240v works for mine
Yep. It's late. If you could get the WH down to 2880 watts, I guess you could use a 15A. But, 110.3(b) may work against you.
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Old 11-14-2009, 10:02 PM   #6
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Originally Posted by jerryh3 View Post
But, 110.3(b) may work against you.
Thanks, I'll look it up.
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Old 11-15-2009, 02:42 PM   #7
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Code question, elec. water heaters


We changed the incoming voltage to 120 when we encountered a similar setup a few years ago. It was impractical to change out the wiring.

That meant the water heater operated at 1125 watts. If starting from a dead cold tank, it would take 8 hours to heat the whole thing. AFAIK, there never was any complaint about not having enough hot water ....
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Old 11-15-2009, 04:44 PM   #8
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I've fed a 4500 watt 240 volt water heater with 120 as well. Like KB stated, it's a bit slow, but it does work.

#14 is OK this way, the actual current is about 10 amps.

I'm sure this violates hundreds of codes, but here's the bottom line; it works, and there's absolutely zero compromise of safety.

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Old 11-15-2009, 05:24 PM   #9
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Thanks, folks. . .
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Old 11-15-2009, 08:09 PM   #10
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Code question, elec. water heaters


Quote:
Originally Posted by Yoyizit View Post
A WH is on #14, which is undersized for a 4500w, 240v element.
If the element is changed to 3300w or lesser wattage is there any reason that the 15A breaker feeding the #14 wire cannot stay?
I realize the recovery time will be longer.
Using the formula I=P/E you arrive at a usage of 13.75a.; Even if it's considered a continuous load, you'll arrive @ 13.99a.; You should be OK with a 15a. breaker or Cartridge Fuse; But I would still use a #12 wire if it's not too much trouble to rewire. (No matter what) Don't drink and Drive, Ever!!!
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Old 11-15-2009, 08:40 PM   #11
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Code question, elec. water heaters


It IS considered a continuous load, and 3300w load would require a branch-circuit rated at 17.1A. For the 14AWG circuit, the limit is 2880w as jerry said.

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Last edited by williswires; 11-15-2009 at 08:42 PM.
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