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burning out transformers

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ruralman
ruralman Member Posts: 5
in THE MAIN WALL
We have replaced the transformer 4X on a Weil-McClein spark ign hot water boiler but it only works for a day or so. Checked wiring according to manual, checked for any irregular/stray voltage on 110v power supply, therm wiring and grounds, also replaced the power module, still can't stop trans from cooking. Anyone run across a problem like this?

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  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,544
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    amp meter

    I would put an amp meter on the load side. Something must be overloading the transformers. You have to find out what that is.
  • Techman
    Techman Member Posts: 2,144
    edited December 2013
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    xformers

    Ohm out both sides of the bad xformers. How about installing a lo volt/lo amp fuse or circuit breaker in the lo volt side ? In the power leg of the 24v xformer.
  • ChrisJ
    ChrisJ Member Posts: 15,706
    edited December 2013
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    Homeowner

    I'm a homeowner and not a pro so keep that in mind.

    However the first thought I had was does the thermostat have a common going to it and have you inspected the thermostat wiring and the thermostat?  If it has a common I see no reason the thermostat and or its wiring couldn't randomly cook transformers. 



    Just an idea I figured it couldn't hurt to offer.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Zman
    Zman Member Posts: 7,569
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    Fuse

    For starters, put a fuse on the LV side. Fuses are cheaper than transformers.

    Did something else change in the system?

    A new t-stat?

    Carl
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Tinman
    Tinman Member Posts: 2,808
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    Is the...

    transformer being used specifically flor the controls within the boiler? Not any external zone valves or relays? The fuse idea is really a must and you need to find out what the amp load is on the secondary. Any water drips within the boiler cabinet? Solid wire connections on the primary and secondary circuits?
    Steve Minnich
  • ruralman
    ruralman Member Posts: 5
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    burnt transformers

    Thanks for the advice and suggestions. There have been no changes to the system according to the home owner, no zone valves (single zone), and no voltage coming back from the t-stat. Should I  install fuses on both wires coming out of the lo-volt side of trans? What would the ohms tell me?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
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    Ohms law...

    See this



    http://commons.wikimedia.org/wiki/File:Ohm's_Law_Pie_chart.svg



    If you know 2 things, you can find the third.



    Transformers are rated in VA, which roughly equals Watts.



    If you know the voltage, and the resistance in ohms, you can determine the amperage potential. If it exceeds the VA capacity of the transformer, then you must either reduce load (check gas valve coil) or increase VA of the transformer.



    The Ohms Law pie chart gives you this ability. Grab a calculator, you will need it.



    ME

    There was an error rendering this rich post.

  • M Lane
    M Lane Member Posts: 123
    edited December 2013
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    Check the doorbell

    In my 30 years, I've occasionally seen doorbells wired to the transformer and thus be a really hard thing to diagnose when they have a short.
  • ruralman
    ruralman Member Posts: 5
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    burnt transformers

    I've already checked for any other transformers, traced the t-stat wires from boiler to t-stat, even ran a temp. dedicated feed to boiler to no avail. The homeowner was finally able to get in touch with the original installer and he recommends changing the gas valve.
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
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    LWCO

    Does this boiler have a Guard Dog low water cut off? ( round black cylinder - red and green LED's )

    If it does replace it NOW - they are known to burn out transformers.

    I would think the last part to cause the problem to be the gas valve.

    Wires shorted to ground, bad LWCO or vent damper.
  • ruralman
    ruralman Member Posts: 5
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    burnt transformer

    already eliminated the LWCO from the wiring. The power module does not indicate any problems on the LED panel, it just goes completely blank once the trans. goes.
  • Eugene_Silberstein
    Eugene_Silberstein Member Posts: 349
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    Easier to measure amperage

    Typically, for a 40 VA transformer, the amperage of the control (low voltage) circuit should not exceed. 1.67 Amps (40VA/24V). For a 20 VA transformer, the amperage should be no higher than 0.83 Amps (20VA/24V).



    This is assuming a 24-volt reading at the transformer's secondary.



    As others have mentioned, a fuse on the low voltage side of the transformer is ALWAYS recommended. They are much cheaper than transformers.



    And only one fuse is needed on the low voltage side. No need for two.

    There was an error rendering this rich post.

  • M Lane
    M Lane Member Posts: 123
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    They make

    transformers with a reset button, btw. I keep one in my toolbox for troubleshooting.
  • ruralman
    ruralman Member Posts: 5
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    burnt transformers

    Just wanted to thank everyone for the advice in diagnosing the transformer problem on a Weil-McClein hot water boiler, It was in fact the thermostat line going upstairs. Haven't pulled out the old wire yet, but temporarily moved the thermostat into the boiler room with new wire and it's working. The re-set transformer was a life-saver, I would have gone thru half a dozen more transformers had I not used the re-set type. This is going to stay in my toolbox.
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