Hot water tank tripping reset

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by plumber69, Feb 26, 2020.

  1. plumber69

    plumber69 In the Trades

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    Jun 20, 2014
    Location:
    Prince Rupert, British Columbia
    Tank is 2 years old, elements tested ok for continuity, even drained tank and inspected them. Water gets extremely hot then trips. I changed the bottom element, going see what that does. I heard if an element fails it will still continue to heat water at a lower votage. If thats the case I may have changed wrong element
     
  2. plumber69

    plumber69 In the Trades

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    Don't know if this matters but I was getting 240 at top element before I left and 9 amps on each wire going to the element
     
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  4. hj

    hj Moderator & Master Plumber Staff Member

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    Unless you have 2,000 watt elements, or 480 v. power, 9 amps is too low.
     
  5. plumber69

    plumber69 In the Trades

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    there is 2 wires going to the top element, each wire read 9 amps so im assuming im geting 18 amps to the element. Its 5500 watt element
     
  6. fitter30

    fitter30 Active Member

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    Your amp draw is 9 amps you don't add both wire reading going to 1 element. 5500watts @ 240 vac 22.9 amps
    Watts divided by by volts. Did you check voltage across element?
     
  7. plumber69

    plumber69 In the Trades

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    yes it was 240
     
  8. plumber69

    plumber69 In the Trades

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    So i should get 22.9 amps on both wires. If im only getting 9 amps but 240 volts, what is issue
     
  9. fitter30

    fitter30 Active Member

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    10.5 ohms with wires off is 5500 watt element. Double check name tag on element sounds like wrong voltage. Compare to other element.
     
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    You're getting 9*240= 2160W (more or less depending on your actual voltage), which seems low, but could be okay depending on the actual element used. It's not 18A. All of the current that goes in one side, goes out the other, so they don't add as was said. Essentially, you're measuring along the same wire. It gets a bit more complicated if it's a 3-phase circuit, but essentially, it's a one-phase. 120vac is sort of a fake result of the way the power is supplied. You're actually being supplied with 240vac with a middle tap (neutral) from the transformer.

    Using and understanding test equipment is critical to getting good indications. Heating elements tend to short or open when they're not working right. Their actual cold resistance will change a bit as they heat up, but will give you a good rough idea you can test. Just make sure the power is off and you've removed the incoming wires.
     
  11. gagecalman

    gagecalman Member

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    It sounds like a thermostat issue.
    If the thermostats are working correctly, they will cut power to the element in use when the set temperature is reached.
     
  12. plumber69

    plumber69 In the Trades

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    top thermostat was changed
     
  13. Reach4

    Reach4 Well-Known Member

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    Location:
    IL
    Bad element, or bad meter.

    EDIT: you are clamping around one wire at a time, right? If you clamp around both, you should read zero normally.
     
    Last edited: Feb 28, 2020
  14. gagecalman

    gagecalman Member

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    Baltimore, MD
    Have you checked the lower?

    I don't understand how the elements are getting power if the thermostats are working properly. If they are set to 120° and the water is getting extremely hot and you still have power going to the elements then there has to be something wrong with the thermostats or the way they are wired.
     
  15. JerryR

    JerryR Member

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    Location:
    Florida
    Bad element or bad thermostat.

    With power off and wires disconnected to the elements Ohm out the elements across the screw contacts and Ohm out each screw to the water heater inner case.

    A shorted element WILL heat up water slowly until the overtemp trips.

    Element will always have power to one connection. When thermostat calls for heat the thermostat puts power to the other connection. A shorted element can have a short to ground and therefor be powered with 120 volts and slowly heat up water until the overtemp on the top thermostat trips.
     
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