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Thread: Single element thermostat on dual element heater

  1. #1

    Default Single element thermostat on dual element heater

    I've determined that the lower element is bad on a 10-year old State water heater (a Franklin, TN model). I plan to replace the heater with a Bradford-White, based on the recommendations here ... but I'd like to wait a few months until the attic temps are more rational (they're in the 100+ range in the summer)!! (Texas summers are HOT, and this summer is abnormally so -- we've had 34 100+ days already)

    My question: Is there anything wrong with the idea of simply replacing the upper thermostat with a single element model, and only using the upper element? This isn't our only water heater -- it only supplies the kitchen and laundry room, so it's not used nearly as much as the one that supplies our bedrooms and jacuzzi. It seems this would let me defer the replacement until Nov/Dec, when it's much more reasonable to work in the attic. Any "bad" things to be concerned about if I do this?

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Default heater

    A new element will cost less than a thermostat, but if you wish to deactivate the element, just remove the wires from it and put wire nuts/caps on the wire ends.

  3. #3
    TROJAN WORLDWIDE SALES RP MACPLUMB 777's Avatar
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    Exclamation Electric water heater

    How would you like to have the space shuttle " CHALLENGER "
    taking off in your house ! !

    All the water heater over heat safety controls are build into

    the upper thermostat ! !

    Google water heater explosions for your self ! ! !

    JUST TURN THE LOWER THERMOSTAT TO IT'S LOWEST THEMPERATURE THE WAY YOU HAVE THE SAFETY CONTROLS

    AND EVERY THING IS OK ! AND YOU CAN JUST TURN IT BACK UP IF YOU DECIDE YOU DON'T LIKE THE SETTINGS
    Last edited by MACPLUMB 777; 07-29-2009 at 08:33 AM.

    MACPLUMB 777

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    35 YEAR MASTER PLUMBER, HEATING, ELECTRIC, DRAINS, FIRE SPRINKLERS, WATER HEATER
    AND BOILERS SINCE JAN, 1989

    281-706-1631 7 DYS A WEEK SALES AND TECH. SUPPORT
    Trojan Worldwide Web Site


     



  4. #4

    Default Replacing the element question

    Yes, I know the safety controls are on the upper thermostat --my question was simply could I just use a single-element thermostat (which also has the safety switch, etc.). It sounds like the answer is Yes ... but I can also just use a dual-element thermostat and not connect the bottom element.

    As for replacing the lower element ==> I was thinking of doing that; but everything I've read (in this forum and others) basically says you shouldn't do that on an older unit -- that it's likely to cause it to start leaking. Is that wrong? I've never replaced an element, but it certainly looks pretty simple -- just buy a new element and the tool to unscrew/screw them, drain the tank, and take out the old/insert the new ... is it really that simple?

    As I noted, the unit's more than ten years old -- would you still repair it? ... or should I simply replace it (as I was assuming I should).

    I want to do what's best -- but don't want to spend unnecessary $$.

  5. #5

    Default Update -- and follow-up question

    Okay, I simply disconnected the two wires that lead from the upper thermostat to the lower thermostat & element and re-applied power to the unit.

    It now works "perfectly" -- but obviously with only the upper element.

    Other than the fact that it now has only half the heating power, is there any disadvantage and/or danger in using it this way? We do NOT use enough hot water from this tank for the longer recovery time to be an issue. It basically supplies the dishwasher (one load per day at most -- sometimes less) and the washer (a few loads per week ... there are only two of us).

    I know a lower element is only $8 or so -- but if replacing it adds to the risk of causing a leak in the tank ... and if it's okay to run with just one element, then I'm inclined to simply leave well enough alone and use it like that until the upper element gives out; the tank develops a leak; or I just decide to replace the whole unit.

    Thoughts??

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    Most electric WH only use one element at a time. It will switch to the upper one (closest to the outlet) to try to extend the useable amount. The bottom one is used to sustain the normal standby. By only using the upper element, you are relying on conduction rather than convection to move the water around an dheat the full tank...it won't react as well since it may need to shut off to prevent overheating th etop before the bottom comes up to temp.

    Ever tryed to boil a pot of water with a torch from the top? It doesn't work as well as heat on the bottom.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #7

    Default

    Yes, I'm well aware that effectively I've turned a 50 gal tank into perhaps a 25 gallon tank in terms of the actual amount of hot water, since it's being heated from the middle.

    But it does seem to be working just fine -- and as I noted we only use the water heater on this side of the house for the dishwasher and laundry room ... so it's very under-utilized (Our other hot water heater is a 2-yr old 80 gallon unit that is used much more ... master bathroom, jacuzzi, guest bedroom).

    My question was really whether it's okay to use like that in terms of safety ... but clearly it is, since the reset switch and thermal cutout are on the top thermostat, which is the only one now being used.

    Based on several comments I've seen r.e. the potential for inducing leaks by replacing elements on older units, I think I'll just leave the bottom element alone and use this with the single upper element until I decide to replace the whole unit

  8. #8
    Plumber Cass's Avatar
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    Default

    The only time a lower element will leak when replaced is if the element is leaking when you replace it...I have never replaced an element that wasn't leaking and had it start leaking...never...

  9. #9

    Default

    Thanks -- that's good to know. I think I'll just go ahead and risk replacing it then in a couple months (when the attic gets tolerable to work in). Might save me the cost of a new heater ... worst case is I have to buy one now instead of in a few months

  10. #10
    Moderator & Master Plumber hj's Avatar
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    Default heaer

    Actually, you have turned a 50 gallon heater into a 12 or 16 gallon one because the upper element is a long way above the center of the tank and it does not heat water below its level.

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