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Thread: 120V 20 Gallon Electric has me stumped.

  1. #1
    DIY Junior Member synack2's Avatar
    Join Date
    Mar 2012
    Springfield, OH

    Unhappy 120V 20 Gallon Electric has me stumped.

    I have a Little 20 Gallon 120V 2000 Watt. Electric with a Single Element. It is only about 3 months old. I have no hot water or maybe just a tiny bit warmer that the cold watter comming in but not much, probably just adjusting to room temp.

    I am an Electrical Engineer so I have a fair amount of electrical Knowledge. Here is what I have done.

    For 120 Volts @ 2000 Watts, I would expect to see 7.2 Ohms of Resistance on the Coil, and about 16.6 Amps of current drawn.

    I removed all the connections from the Element. Measured it, and got 7.23 Ohms (Joy)

    Measured both contacts on the element to the ground wire and the cold water pipe and got Infinite reading (No Shorts - Joy)

    Hooked Element back up and plugged it in. Hear Expansion sounds like it is heating up. Test the voltage to the element and got 120Volts (Joy)

    Waited an hour no hot water. Thought maybe it is plumbing related and the water is hot. I turn off hot water outlet and turn on hot water faucet and no water flows, so I have ruled out a crazy washing machine or something bridging the system. I then trip the pressure release valve a little and the water is cold.

    Hmmm... Well I figure the only other test was to see if the element is drawing current, and how much its drawing. I snap the amp clamp on the black wire and get 16.7 Amps and the white wire and get 16.7 Amps and the Ground Wire and get a .002 Amps (Looks good to me - Joy)

    Wait 2 hours, and test for hot water - still cold (NO JOY)

    When working I would get from cold to hot in about 45 Minutes.

    I am saying at this time if electric is present and flowing at the element and there is no hot water it has got to be the element no matter that all of the readings look perfect. Anyone have any other Ideas?
    Last edited by Terry; 03-02-2012 at 04:57 PM.

  2. #2
    Nuclear Engineer nukeman's Avatar
    Join Date
    Nov 2009


    Are you sure the shutoff is on the hot side? Usually it is on the cold (inlet side).

    The energy has to be going somewhere. We know from Ohm's Law that if we are pulling current and have a voltage potential, that it is going to become heat (or some energy form). From your measurements, you are putting 2 kW into it, so something should be getting warm. It appears that:

    1. The hot water is leaking somewhere (crossover to cold, etc.)
    2. Element covered with deposits and slowing the heat transfer. Doesn't seem likely based on the age of the unit. It would still eventually get hot anyway. The assumes the the t-stat is working correctly and keeping the element going.
    3. Relief valve - can you see where it goes? If it was sticking/dripping and directed into a drain where you couldn't see it, your HW could be leaving that way.

  3. #3
    Test, Don't Guess! cacher_chick's Avatar
    Join Date
    Jan 2008
    Land of Cheese


    Your electrode is hot. The water in the tank will never get hot if water is running.

    Any piping going into a slab?

    Assuming the shutoff valve is on the inlet (where it belongs), if there were a leak, you could shut the valve to stop flow and the water in the tank would heat.

  4. #4
    DIY Junior Member BrianK's Avatar
    Join Date
    Jun 2012
    Calgary, Alberta, Canada


    Is it possible that whoever installed the unit mixed up the hot and cold supply and discharge. I had a plumber come in to install a second HWT and couldn't get any hot water out of it because the dummy installed it backwards. What was happening was that the cold water was coming in the hot side and immediately going to the bottom of the tank where it would just go up the dip tube - so it felt like there was no hot water. I know your symptoms aren't exactly like mine but just thought I'd share my experience.

  5. #5
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    Turn off the water supply to the tank and see if it heats up. It appears you have a hot water leak which is draining the hot water faster than the heater can make it.
    Licensed residential and commercial plumber

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