Nuisance electric water heater over temp trip

Discussion in 'Water Heater Forum, Tanks' started by rshackleford, Apr 15, 2012.

  1. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    My hot water heater has a mind of its own.

    It used to only happen when we went on vacation but now it's about every three weeks.

    The water will get really hot and the over temp safety will trip. I will have to wait for it to cool and then reset. This will go on for five or six days and then stop. It will then work normally for several weeks.

    It is a dual element electric.

    How do I fix?
  2. nukeman

    nukeman Nuclear Engineer

    Messages:
    709
    Location:
    VA
    Sounds like a defective t-stat. If it isn't detecting the temperature correctly or thinks the setpoint is higher than it is, the elements will continue to run and heat beyond the temperature setpoint. What ballvalve is saying is that the parts are cheap and easy to replace on an electric WH. You aren't out anything but a little time and money to replace the t-stat(s). It will probably fix it. If it doesn't, you at least know that it wasn't the cause.

    An electric WH is nothing but a power supply feeding it, a couple t-stats to control the elements, usually a pair of elements for heating, and an overtemp limit trip (for safety). They are simple devices and are cheap to repair (outside of a failure of the tank itself).
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    Have a plumber test ALL the components. A failing element can cause the problem, but so can a loose screw on the thermostat. IF you just start replacing parts, you may still NOT cure the problem.
  4. rshackleford

    rshackleford New Member

    Messages:
    284
    Location:
    Eastern Montana (The Bakken)
    How should the two thermostats be set? should they be the same or one higher than the other?
  5. Hackney plumbing

    Hackney plumbing Homeowner

    Messages:
    1,174
    Location:
    Alabama
    If the element is grounded it can run all the time until it fails. This can/will cause the heater to over-heat and the high limit to trip. I doubt thats ur problem.

    The thermostats should fit tight against the tank. The insulation should be in place over the thermostat and the exterior cover panels should also be in place.

    I suggest the upper and lower thermostats match in temp settings.

    You probably have a bad upper or lower thermostat.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    quote;
    dying elements do not overheat, they underheat, and leak electricity into the water until they fail totally. Loose screws might cause an arc and a melt, but again it will not overheat the element itself.

    Either you do not repair many heaters or you just replace everything. IF an element burns out NEAR the terminal controlled by the thermostat, it will use the water as a neutral source and heat continuously, although at a diminished rate, which is why it take longer for the high limit to trip and shut off the power. IF the screw/bolt on the high limit control is loose, the added resistance WILL overheat it and cause it to trip, regardless of the water temperature. When this happens the guilty bolt will usually change color.​
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    It's not uncommon for one leg to be connected to the heating element at all times and the other through the thermostat, and if it is working properly, no current will flow unless the thermostat calls for it. But, if there is a path to ground or neutral because it is holed, or damaged, you'll get current flow from that one leg to neutral. As said, it won't heat as fast, but it sure will overheat since it won't shut off.
  8. JerryR

    JerryR Member

    Messages:
    235
    Location:
    Florida

    WRONG. WRONG. WRONG.

    Look at the wiring in the link you provided.

    There is ALWAYS a hot leg at each element (red and blue line in the diagram in your link) unless the OVERTEMP BREAKER POPS i.e. ECO reset trips.

    In the diagram in your link;

    If WH is not up to temp setting, then upper thermostat only switches left leg through T2 to upper element left screw or through T4 to lower element left screw to complete a 240 Vac across the element.

    Unless overtemp reset trips, you WILL have a 120vac phase at one of the element lugs ALL THE TIME.

    BE CAREFUL OUT THERE.
    Last edited: Apr 23, 2012
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    quote; "blown elements" heat at a reduced pace until they trip the breaker BECAUSE they are 2 pole switches that break both wires. Wanna work on a water heater with one hot wire always on the element?

    If you work on a water heater, (and I assume from your statements you have NEVER worked on, or tested, one), which has power to it, one hot wire to each element will ALWAYS be hot, because the thermostats ONLY break one leg. Other than the high limit which IS a DPST switch. I would advise you to NOT give advice regarding water heater repairs, because you WILL get someone electrocuted.
  10. JerryR

    JerryR Member

    Messages:
    235
    Location:
    Florida
    You don’t have to get rude you know....

    My GE Dual Element water heater is wired exactly like the one in your link, wire colors and all.

    I just put a meter across the upper element with water heater up to temp and not calling for heat.

    Across the two lugs on the upper element I read 0 VAC, i.e. element is NOT heating the tank.
    BUT, When measured from either element lug to GROUND the meter reads 121 VAC...BECAUSE terminal "L4", where the BLUE and RED wires are connected, is HOT ALL THE TIME!!!!



    The upper element and lower element thermostats in your link and in my Water Heater are Single POLE, Double Throw, SPDT Look at the attached diagram of the upper element thermostat you linked to and compare it to this SINGLE POLE Double Throw.
    http://en.wikipedia.org/wiki/File:SPDT-Switch.svg

    A Double Pole single throw has two sets of contacts that are switched like this one:
    http://en.wikipedia.org/wiki/File:DPST-symbol.svg

    Jerry

    Attached Files:

    Last edited: Apr 25, 2012
  11. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    First, you have to know how to use a multimeter! When not calling for heat, even though there is voltage applied, there is no continuity, so no current. The thermostat only opens or closes one leg of the heating element. Since it is a 240vac device, measuring across it will read zero UNLESS you connect one probe to ground, which then creates a circuit and reference for the meter to actually measure the voltage...since there's no current when off, there is NO voltage difference between the two legs of the element, but definately IS voltage from (either) leg to a ground point. And, that was the whole issue...if for some reason the element became grounded, if it didn't short out and trip the breaker, the current would always flow from the hot side to ground, increasing the water temp until the overtemp safety switch removed power from BOTH sides until reset.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    quote; First, you have to know how to use a multimeter!

    No, first he has to know how to read a wiring diagram, otherwise he is going to electocute himself. He has absolutely NO idea of how water heaters are wired or HOW the thermostats work, therefore, he WILL touch a "live" circuit because he THINKS the thermostat has interupted the power.
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    Maybe this will help: http://eet.canton.edu/~eet/Sequence%20hot%20water%20heater.pdf

    Notice that power from one leg goes to one side of EACH element (after the high temp limit switch which DOES remove power from both legs, but it's the only thing that does). The thermostat determines which element and when it applies power to the other side of the selected element to actually heat the water.
  14. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    quote; Name a 220 volt appliance that shuts off only one leg of a hot circuit. Mexico does not count.

    A water heater, for one, and some baseboard heaters depending on which thermstat they use. I hate to have a battle of wits with an unarmed opponent. As the farmer said, "It doesn't do any good to wrestle with a pig, because all that happens is that you get dirty and the pig is happy". You do NOT know what you are talking about, and if the heater elements are ZERO voltage to ground then you have the only water heater in existence that way, because the upper thermostat would need SIX terminals, in additon to the ECO, and the bottom one would need FOUR of them, and YOUR heater does NOT have them, nor is there any thermostat made which is like that.
  15. JerryR

    JerryR Member

    Messages:
    235
    Location:
    Florida
    Here is the sequence from Jim's link from the State University of New York, Canton, Electrical Engineering Technology Department. I highlighted the description about there ALWAYS being 120 VAC to both elements.

    Notice that while Canton is pretty close to Canada, it is nowhere near either Bangladesh or Mexico. :eek: :p

    This description agrees with my understanding of the circuit diagram and with the readings taken with my Fluke Meter.

    Attached Files:

  16. JerryR

    JerryR Member

    Messages:
    235
    Location:
    Florida
    Imagine this as true, because it is. That is what everyone has been trying to tell you all along. Perhaps now you will believe it.

    See, anyone can learn something new almost every day, no matter how much one thinks he/she knows it all.

    Single Pole Thermostats and are used in dual element GE, Rheem, Ruud, Richmond, AO Smith, American, GSW and Whirlpool heaters AND they meet UL- and CSA listed code.

    I would really like to see a picture of the thermostat in your double element water heater where it is a Double pole device. Is this an Industrial or European water heater or were you just mistaken?
  17. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    I tested an old ray pac commercial, and it has a control box with relays. Now I know that cost is an issue for residences, but we both know a life is worth a little more than a double pole switch. I assumed that engineers would care about the safety at the residential elements.

    Would you install a 240 circuit breaker without the connection between handles so that one line would remain hot? I see a sweet deal from UL to the waterheater guys so that they can make them in mexico of tin cans and up the profit so that the "head" of GE can take home a few billion a year. Nice to have 22 vacation homes for the sake of a 6 cent killer switch.

    Ethical bankruptcy. Hey: send it to China, then no liability need apply.
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    A WH should not be worked on unless you remove power to it...one shouldn't assume it is safe if the thing isn't calling for heat. Same is true with your furnace - it's ready to go - power running around inside, just waiting for the thermostat to call it into action. IOW, it is a system, it works fine, just don't muck around inside unless you know what you are doing. Under normal circumstances, it is totally safe until you take the safety covers off - THEN, you better know what you are doing. Same thing is true with almost anything electric or electronic...it's safe until you break it open.

    Even older table lamps with screw-in bulbs that didn't have a polarized plug could kill you when replacing a bulb if you happend to do things just so.

    There's a reason why there are safety warnings on electrical appliances...read and heed.
  19. JerryR

    JerryR Member

    Messages:
    235
    Location:
    Florida
    Jim,

    BINGO

    Before retiring, I managed a service organization. We seviced all kinds of heavy duty equipment. One device had 3 phase 240 Vac 100 amp supply, and as long as the safety covers are installed it was safe electrically. Also we had some 480 volt 100 amp equipment installed which my reps serviced. Remove the covers on any of these devices and you expose yourself to some pretty hefty live contacts, just like a water heater with covers removed.

    Electric water heaters have historically been exceptionally safe electrically as they are currently designed and manufactured. Of course this assumes that one understands how they are wired and follows proper servicing guidelines. I just did a quick search and found that in a 4 year period there were 12 electrocution deaths directly related to electric water heaters. I would not be surprised if these all were unqualified people trying to service one with the safety covers removed. Reguardless that is a pretty low number. My other hobby is as a private pilot. In that same time period there were almost 1,500 people killed in the US in private aircraft accidents.
  20. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,292
    Location:
    Cave Creek, Arizona
    A "commercial" water heater with "relays" is a completely different device than the standard one or two element water heaters. The thermostat is STILL a single pole device, but the relay will break ALL the conductors. You are trying to tell us that we have to change the wheels and tires as a unit on our cars, but you are referring to a Bugatti Veryon, NOT a Honda Civic.
    Last edited: Apr 30, 2012
Similar Threads: Nuisance electric
Forum Title Date
Water Heater Forum, Tanks Rheem Performance 30 gal. Short 6 Year 4500/4500-Watt Elements Electric Water Heater Jun 13, 2014
Water Heater Forum, Tanks Dielectric / heat stopper failure? May 6, 2014
Water Heater Forum, Tanks Electric water heater in series with boiler Apr 7, 2014
Water Heater Forum, Tanks Which Electric Tank WH Rheem Model at Home Depot? Model Breakdowns Inside Apr 4, 2014
Water Heater Forum, Tanks Need a new electric water heater Mar 26, 2014

Share This Page