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Thread: Rheem Water Heater has me stumped!

  1. #1

    Default Rheem Water Heater has me stumped!

    Heater 3yrs old
    electric
    30 amp double pole breaker
    120 volts each leg breaker
    120 volts each wire at heater
    new thermostat
    new elements
    120 volts each side thermostat
    120 volts each side of top and bottom element
    reset pushed
    NO Hot Water
    Help

    Thanks
    lizzydog

  2. #2
    Plumber jimbo's Avatar
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    Measuring each leg of a 240 volt circuit, to ground or neutral, will throw you off. You never know when you are reading across an open.

    You need to see 240 across the two terminals of an element. If it is not 240, it will not heat....period. Something is open.

  3. #3

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    Try turning the breaker all the way off and then, all the way back on. Check the top 2 scews of the top thermostat at the same time and you should have 240 volts.

  4. #4
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by lizzydog View Post
    120 volts each leg breaker
    120 volts each wire at heater
    new thermostat
    new elements
    120 volts each side thermostat
    120 volts each side of top and bottom element
    reset pushed
    NO Hot Water
    Help

    Thanks
    lizzydog
    Each 4500w element should read 240/4500 = 13Ω.
    Voltages measured with respect to ground?

  5. #5

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    12.80 you rounding?

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Well, few meters out in the field can read that accurately, plus, the resistance will be different than that when cold verses energized...but, close enough.

    Don't try measuring resistance with the power on unless you like sparks and value the meter (the fuse should blow, but you never know).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #7
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by Cookie View Post
    12.80 you rounding?
    That I be.

    There is also Significant Figures, which is a little harder to 'splain.

    120 could mean between 119.5 and 120.4 [3 significant figures] or it could mean 115 to 124 [two significant figures] in which case the '0' is just a placeholder. I took it to mean two figures and so the answer should be the same number of figures. Since the 120 varies by 5% or 10% this is plenty close.

    We nerds get around this by using scientific notation, so 1.20 x 10 is 3 figures and
    1.2 x 10 is 2 figures and 1.20000 x 10 is 6 figs.
    Last edited by Thatguy; 05-05-2009 at 06:53 PM.

  8. #8
    Plumber Cass's Avatar
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    WoW...were trying to fix a water heater not fly to the moon....

  9. #9
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by Cass View Post
    WoW...were trying to fix a water heater not fly to the moon....
    Rum does that to me

  10. #10

    Default Rheem waterheater has me stumped

    Thanks for all the information. The new 30 amp double breaker was bad.

    lizzydog

  11. #11
    Moderator & Master Plumber hj's Avatar
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    Default heater

    WHO measures resistance? If the element has 240 volts and the amperage is ZERO the element is bad. It it reads in the neighborhood of 18 amps it is good. AND both leads have to read the same amperage.

  12. #12
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by hj View Post
    WHO measures resistance?
    Nah, he's on first

    I figured more people have ohmmeters than clamp-on ammeters and more people prefer to make unpowered measurements.

    240v/18A = ~13Ω.
    Last edited by Thatguy; 05-09-2009 at 09:53 AM.

  13. #13
    Master Plumber Redwood's Avatar
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    I test like HJ does...
    Seems to work for some reason...

  14. #14
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by Redwood View Post
    I test like HJ does...
    Seems to work for some reason...
    What's also is in your favor is that a water heater element doesn't fail in many different ways.

    I doubt that the element resistance changes in value and it's unlikely that the resistance element shorts to the grounded element tube because of all that ceramic insulator packed in there, so your choices for resistance/current flow are 13 Ω/18A or infinity/zero.

    It's pass/fail.

  15. #15
    Master Plumber Redwood's Avatar
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    Oh elements do short to ground.

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