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elements burning out prematurely

foxm
foxm Member Posts: 1
I am new to this. Using a 36 litre HW tank single element (4500w) lasts about 2 weeks, then burns out(3). Basement floor 1 1/2-2" Styrofoam with 6 mil vapor barrier underneath. 4 zones 180-190' lengths, single pump. Brings floor temp up to 64 F before it burns out. Not used as a main heat source, just to warm up the slab. I purged each zone 30-45 min each with last element. Any advice or suggestions or if further details needed? 

Comments

  • icesailor
    icesailor Member Posts: 7,265
    Burn-Outs:

    So, you took a 9 or 10 gallon electric water heater and tried to use it as a hot water boiler.

    Some here might have said that it might work for you. We haven't seen it work well for anyone else but it might work for you.

    Sounds like it didn't. Electric water heaters aren't boilers and are designed to heat potable water. They make electric boilers that are designed to be used as boilers.

    Water heater elements burn out for one main reason. Lack of cooling fluid (water) around the element. The two biggest ways I see this happening is by turning on the power with an empty tank (devoid of water). The elements burn out in a very short time. Like a minute or two with a 4500 watt element. The other way is by the fact that there are a lot of dissolved solids in the water that precipitate out of the water when heated by the element and the solids form on the element. Insulating the element from the cooling water.

    IF, after some period of use, the now used element sounds like it is sizzling inside the tank, and after it blows, it will look either one of two ways. The element is hanging down and shiny bright (it can be broken in the middle) or it is all encrusted with iron or some other foreign substance and somewhere on the encrustation, you will see a hole where the electricity blew through.

    If you are using this water heater as the ONLY source of heat energy for your floor warming and NOT in any way for potable water, there are metals breaking down in the system, causing the fouling of the elements.

    If you are using the water heater to also heat potable hot water for human use, disconnect it immediately from the potable water system because you can make yourself and anyone else that comes in contact with the water extremely sick and die.

    One other issue that you face with using electric water heaters for boilers is system pressure. If you run the system at 12#, there isn't enough system pressure to stop overheating of water around the element. Water heater elements don't overheat with 50# tank pressure. They might at 12# where the boiling point of the water is 245*.



    You probably got the information on how to build your system on a DIY forum. It isn't working. Tell that forum and it isn't working and see what they say. I'd be interested to hear their responses as to why it isn't and how to resolve it.

    If the water is rusty, there's your start. Have a Cast Iron circulator in the loop? There's another place. Steel piping mixed with copper and PEX?
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    elements

    When you say burning out - are they melted looking or just won't heat up?

    If they are melted then I would say you are somehow running them dry.

    If they are just not heating up then check to make sure that you have the right element for the voltage you have.
  • icesailor
    icesailor Member Posts: 7,265
    Elementry, Elements.

    I'll bet I have replaced over 200 elements in my career. They were all replaced because they overheated from calcification around the element, causing over heating. Or someone turning on the power to an empty tank.

    If I find a water heater that isn't heating, I first check for voltage at the element, then put my "Wiggy" on it. If there's voltage there, and no amp draw, it has ALWAYS been the element. If the voltage is on one side (not 220), I check the thermostats and the HTC. If the HTC is popped, it is the bottom element running and the bottom thermostat stuck closed. If the bottom element has one side, its the lower thermostat stuck open.

    Even a 10 year old element that fails is caused by corrosion through the outer covering and a short or the element becoming encrusted and overheating locally on the element.

    The amount of elements he has gone through suggests that his open radiant system has a Cast Iron circulator pump and steel piping and copper piping.

    The water is probably a nasty brown.



    As far as element voltage is concerned, he said that he was blowing 4500 watt elements. They don't make a 115 volt element that is rated at 240 volts. It would require a 60 amp breaker for protection. He may have a 110 volt heater (if it is 10 gallons) but if you connected it to 220, it would blow somewhere in the heater and the wiring would melt down. If he connected it to a 4500 watt element in a 110 volt heater ( a possibility for a DIY'er,) the amp draw to a 110 volt breaker would probably trip it.

    Its my experience that when what is happening to him is happening, under the conditions he describes, it's a serious case of oxygenation,  causing the steel piping and cast iron to return to its powdered state.
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