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Can I plug my new eemax SPEX3512 Point-of-use tankless water heater with these Specifications Volts: 120V kW: 3.5kW Amps: 29A Temp Rise F at .5 GPM: 48 Degrees Recommended Wire Size: 10AWG

Into a regular house bathroom GFI outlet that is most likely 15A and 12AWG wire?

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    Not if you expect it to work and/or not burn your house down.
    – brhans
    Commented Aug 31, 2020 at 0:47
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    That appliance will need a dedicated circuit....why are you wanting to put a point-of-use heater in anyway? Is this going to be the sole source of hot water for this bathroom, or a booster heater? Commented Aug 31, 2020 at 0:48
  • Thank you for your input. Yes, this bathroom is for an office, and there’s only one sink for hand washing.
    – Michael
    Commented Aug 31, 2020 at 10:04
  • @downvoters - Don't downvote questions just because the answer is emphatically "oh god no" - such questions are somewhat likely to attract great answers, as this one has. Commented Nov 10, 2022 at 17:46

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First off, I can't imagine it came with a plug attached that would fit a 120 Volt outlet. Secondly, if it did, it would trip the breaker very fast, as soon as the 29 Amps hit that 20 Amp breaker. If you're trying to jury rig it, don't.

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  • Thank you for your response. Sorry, I should’ve been clearer. The unit came with no cord. Also, it for a small office bathroom that only has one sink and no hot water. It’s for hand washing only.
    – Michael
    Commented Aug 31, 2020 at 10:08
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    @Michael You'd need a dedicated circuit of #10 AWG and a 30 Amp breaker (or whatever the instructions call for).
    – JACK
    Commented Aug 31, 2020 at 12:29
  • And heaven forbid you connect multiple circuits to that unit to "add up to" the amperage. You will burn down the room down, void all warranties and insurance, and generally have a very bad day.
    – Nelson
    Commented Sep 1, 2020 at 3:47
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The answer is "NO".

Now actually, with GFCI receptacles, it's a little more complicated than that (but not enough to help). GFCI receptacles are not circuit breakers and they don't even know how much current is going through them (unless it's unequal). In fact, due to a UL requirement, that 15A GFCI is rated for 20A through it, e.g. two 10A loads. But 30A is out of the question.

This is a silly unit because it requires a dedicated circuit, but it is only 120V. Normally a 3500W heater is wired 240V @ 15A, (twice the volts half the amps) so you can use the cheaper #14 wire. 30A@120V circuits are far more unusual than 15-20A@240V circuits, do this was sure to be a new dedicated circuit in any case. The rise@flow rate is rather poor, unsurprising given the low power requirements. It is weak even for a hand wash faucet; a shower is out of the question.

This is a classic problem with on-demand heaters. They take A LOT of power, and not grasping this, people far too often spec a too-small unit, resulting in user disappointment and a failed project.

The 120V unit being such an oddity, I imagine you bought it hoping against hope you could plug it into existing wiring. Well, you can't.

You need a dedicated circuit anyway, and the heating elements inside on-demand heaters are the cheap part, so you might as well get a more usefully sized heater of 30A@240V. Nobody ever got fired for buying that one for an office bathroom.

Or if you are willing to sacrifice the existing 120V circuit (commercial bathroom right?), you could convert the circuit to 240V and fit the largest heater it can support.

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    Thank you for your input. I am new to this forum, and this is my very first question. This is fir a small office bathroom that only has one sink for hand washing. It was fitted with a small electric water heater (not tankless) that was plugged into the wall, but that tank died. Black specks started to come out with the water, so we were thinking that a tankless would be a better choice. Obviously I didn’t know that the tankless requires a dedicated circuit. The literature that came with the unit didn’t say that.
    – Michael
    Commented Aug 31, 2020 at 10:21
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The WH you are talking about needs 29 amps at 120 volts. So no way can you connect it to a 15 or 20 amp convenience circuit.

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  • Thank you for your response. I am new to this forum and this is my first question, so I’m sorry if you feel I have not “contributed.”
    – Michael
    Commented Aug 31, 2020 at 10:25
  • @Michael Didn't mean to offend you with that comment, it's one us regulars use a lot here. It's a serious site for questions that people have tried to solve on their own first but need more help or advice. Commented Aug 31, 2020 at 14:57
  • Electrical is a serious business. Bad jobs mean fire, destruction, and sometimes death (yourself or others). Do not ever think "Oh, it's close enough". Don't do weird stuff that you think will work, because by the time you find out it doesn't work, there will be, minimum, fire and destruction, and your insurance will definitely not cover it.
    – Nelson
    Commented Sep 1, 2020 at 3:50

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