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Thread: 240V electric water heater on 120v circuit

  1. #16
    Plumber jimbo's Avatar
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    I am sure our electricians will chime in on this; my impression was that a water heater was classified as a continuous load and therefor you could not put 19 amps on a 20 amp breaker. Certainly in my experience, I have seen 30 amp breakers on 4500 watt units. I suspect the manufacturer calls for 25 amps, and due to those being scarce, the installer usually does 10 guage wire and a 30 amp breaker. I think your only out would be to replace the elements with 3500 watts, but that is low for a 50 gallon. And that may not comply with code either, due to the fact that the unit was factory built as a 4500 watt.

    Let's wait and see.
    Last edited by jimbo; 11-27-2007 at 03:26 PM.

  2. #17
    Retired Defense Industry Engineer jadnashua's Avatar
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    You basically have no margin. A little glitch, and the breaker may trip.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #18

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    I certainly do not want a fire while I am here, but I also do not want to have a future tenant to have a fire. I don't need that on my conscience and I do not want the legal headaches that could be involved.

    Can you get by with it? Yeah but....... In theory the breaker will protect it but I wouldn't suggest it.

    When you sell your house be sure to disclose IN WRITING that the W/H needs to have a proper 30 amp circuit run to it.

    If you want to be 100% safe just have it done now (200-600 dollars)

    Do it

  4. #19
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by Alectrician View Post
    When you sell your house be sure to disclose IN WRITING that the W/H needs to have a proper 30 amp circuit run to it.
    Yeah, but in today's world of home inspectors they'll surely demand YOU pay for it.

  5. #20
    In the Trades Bob NH's Avatar
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    The circuit will work but is a violation of the National Electrical Code. I have copied the relevant parts below.

    422.10(A) . . . "The branch circuit rating for an appliance that is continuously loaded, other than a motor operated appliance, shall be not less than 125% of the marked rating, . . .

    422.13 Storage Type Water Heaters. A fixed storage-type water heater that has a capacity of 450 L (120 gal) or less shall be considered a continuous load.

    The heater element will draw 4500 Watts/240 Volts = 18.75 Amps.

    18.75 x 1.25 = 23.44 Amps. Therefore it must be operated on a circuit rated for at least 23.44 Amps. The available wire size is 10 AWG so you need a 10 AWG wire. It may be protected by a breaker up to 30 Amps.

    12 AWG wire has a current rating of 25 Amps at 60 C (Table 310.16) so it should not overheat at the rated load. However, other provisions of the code prohibit using it above 20 Amps.

  6. #21
    Moderator & Master Plumber hj's Avatar
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    USe it as it is now set up. There is no fire danger. If the circuit breaker starts tripping, then have a plumber install small wattage elements. That is how Sears and others make their heaters "energy efficient".

  7. #22
    DIY Senior Member Mike Swearingen's Avatar
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    Listen to these electrical pros. (I'm not one, just a long-time DIYer and a 20+year NC real estate broker.)
    You may get by with what you have now, but you most definitely WILL have a problem when you or your heirs sell this house (with a buyer's licensed General Home Inspection or licensed Electrical inspection).
    GHI's are usually very thorough around here, especially on the electrical systems, and they would promptly flag this as a "code violation and safety hazard", which a buyer (and their lender if they're made aware of it too) would require that this be re-wired to code, most likely at seller expense.
    A seller may legally refuse to do any corrections, but that gives the buyer a free "get out of the contract with my earnest money back" walk, if you don't.
    Also, if you ever have a house fire due to this circuit, guess who's insurance can refuse to pay any damages whatsoever?
    If it were me, I would have this done properly, perferably by another electrician. Your call. "Pay me now, or pay me more later".
    Good luck!
    Mike

  8. #23

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    Yeah, but in today's world of home inspectors they'll surely demand YOU pay for it.

    Of course.

    Like Mike said, "pay me now or pay me later".

  9. #24

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    Stated another way: a 30 amp circuit can supply a single appliance at a maximum of 80% times the rating. 30 x 80% = 24 amps
    20 x 80% = 16 amps So #12 will not work for a 18.75 amp load.

    I think this applies to any single appliance, continuous load or not.

  10. #25
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by ked View Post
    Stated another way: a 30 amp circuit can supply a single appliance at a maximum of 80% times the rating. 30 x 80% = 24 amps
    20 x 80% = 16 amps So #12 will not work for a 18.75 amp load.

    I think this applies to any single appliance, continuous load or not.
    Why 80% twice?????????????????????????????????????????

  11. #26
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by ked View Post
    Stated another way: a 30 amp circuit can supply a single appliance at a maximum of 80% times the rating. 30 x 80% = 24 amps
    20 x 80% = 16 amps So #12 will not work for a 18.75 amp load.

    I think this applies to any single appliance, continuous load or not.
    The only reason that the water heater can't be served by a 20 Amp circuit is the explicit code restriction that apply:

    422.13 Storage Type Water Heaters. A fixed storage-type water heater that has a capacity of 450 L (120 gal) or less shall be considered a continuous load.

    AND the additional code requirement that says:

    422.10(A) . . . "The branch circuit rating for an appliance that is continuously loaded, other than a motor operated appliance, shall be not less than 125% of the marked rating, . . .

    The circuit will work fine but 422.13 and 422.10 make it non-compliant with the code.

  12. #27
    DIY Junior Member miscmail1560's Avatar
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    Default Everything finally fixed

    I have to say it again, I have never found a more responsive or helpful board on the Internet. You guys are great. I will definitely be tuning in and even chipping in my opinions if I think I can help anybody else like you have helped me.

    So, I have good news about my installation. I got my local building inspector to come and look at the setup and they concured with all of you. I also called the estimator for the company that did the work and told me that he would not recommend that setup. I went to the owner of the company and told him both of those facts. Not only did he state that he woudl resolve the issue, but he did so without charging me any additional money. So I have a 30A breaker and 10 gauge wire tip-to-tip. I feel a lot better about it.

    Again, thank you all so very much for your input. I learned a lot, and am very glad that I visited this site!!!

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