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Munchkin foo-bared

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1974bobcat
1974bobcat Member Posts: 18
Looking for some help with troubling shooting a Munchkin. It is displaying the code F00 the manual says it is a high limit control reset after cooling or replace if problem persists. So I did what most of us do to check the limit I ohmed it out. It is CLOSED. So I jumped out the wires and still get same code.

If I shut the power off and back on the fan goes into pre purge and then stops and the code flashes F00. It even go into prepurge w/no call for heat?

I wonder if the 925 circut board needs to be replaced.Any thoughts.

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  • WaterHeaterGuy
    WaterHeaterGuy Member Posts: 80
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    F00

    Take your house thermostat connections off the boiler and tie the two grey TT wires together. If the boiler starts working you have some sort of 24V to ground issue in the house.

    F00 is the first in the boiler's list of fault codes. If you have any 24V dead ground inside the boiler, an F00 is probably what the unit will display.
  • Plumb Bob
    Plumb Bob Member Posts: 97
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    Yes, to confirm, the manual section on F00 is very poorly written. If anything gets grounded that shouldn't be grounded, it thinks there's a limit sensor problem because they all share a common ground. Don't believe the manual. Test the stat line by removing it (as advised above); this is the first thing to do because that's a long wire and there are many places it could get shorted to ground. But it could be many other things as well.
  • 1974bobcat
    1974bobcat Member Posts: 18
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    Thanks for the advice, After a lot of prying the electrician told me his guy put 120v to x2 on the taco panel. So who knows what they did to the zone relay.
  • kevin coppinger_14
    kevin coppinger_14 Member Posts: 2
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    That is why...

    I wire my own boilers....I don't trust 99% of the electricians out there to do the job right! kpc
  • 1974bobcat
    1974bobcat Member Posts: 18
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    I hear you Kevin I was just called in to trouble shoot this one. the electrician just added a zone an next thing you know a day late no hot water. The poor people have thier parrents up for Mothers day and no one can shower. I don't think I can get parts anywhere today.

    I have a feeling that the control board is dead because I did disconnect the TT on boiler and the system still goes in to prepurge. ???
  • ScottMP
    ScottMP Member Posts: 5,884
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    Sounds like

    the board is gone Bob.

    Are you in Mass ?? If you are call Rich Swatton. His number is on the other post about the Munchlkin fan. He is the factory service guy and might be able to help you out.

    Scott

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • clammy
    clammy Member Posts: 3,111
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    F00 the real fix

    The reason you are coding on a f00 code is you did not set the post circ pump purge run time which runs the circ for whatever you set it for (2 minutes to 5 minutes) gives the heat exchanger time to remove some extra heat from the heat exchanger after the burner shuts off .I have found that if you are running high temps for heat or are using the vision one kit with a indirect tank that the remain heat in the exchanger will set off the manual high limit .On your heating side if you are using zone valves and your system pump is running off the boilers circ relay you will have to install a by pass not to dead head your pump (or a dpb valve )If you are using the vision one also remenber to set the indirect post circ run time also ,take a look again in the 925 controller section of the instruction manual and you will see these selectional menu and just program the post running time for both indirect pump and heating sysytem pump after programing thgem your F00 code will be a thing of the past .To reset the hi limit i beleive that the reset buttom on the controller or just turning the power switch on and off will reset it has been a few years since i have had a unit i installed go off on a f00 but i program all of them to have a minuin post run time of a few minutes form the central heating pump and indirect circ pump ,it's no big deal again just read through all of the instruction which came with ht e boiler peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • 1974bobcat
    1974bobcat Member Posts: 18
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    Thanks for the tip. I am in Mass, Tyngsboro
  • 1974bobcat
    1974bobcat Member Posts: 18
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    I under stand what you are saying about the post purge of the circulators. This boiler was install 3 years ago and was running before the electrician touched it. So I wonder if he put 120 to TT and cooked the board. Reason being if I shut off the power and disconnect TT then flip the power on the prepurge fan starts to run and it gives the code F00.
    I checked the sequence of opps in the manual and this is not following what they say should happen.


    BOB
  • clammy
    clammy Member Posts: 3,111
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    things to double chk

    if indeed he did apply 120 volts to the board it in all probalby is cooked i would ohm out the manual high limit sensor ,i cannot remenber if it's a resistor or klickon type sensor if the latter jump it out and see what happens ,did you also chk the board fuse ,i also never let electricain wire my boiler if they insist (cause they want to hammer the GC or HO)then i let them know that they will be totally responable for all cost assscoted with repair then they usually then back off .Also just go over all low voltage wiring to make sure that he is not powering zone valves or any other low voltge off the tt connections on theboiler .In all cases that i have experenced with f00 code where all asscoted with the fact no one programed the post circ times as stated before the foo code is usually always assocated with manual reset hi limit also don't rule out that the sensor may be bad causing the unit right at start up to go through it normal fan pre purge before coding f00 peace and good luck hope i helped clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • Dennis
    Dennis Member Posts: 101
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    Check to make sure the polarity of the 120 volts is correct.

    > if indeed he did apply 120 volts to the board it

    > in all probalby is cooked i would ohm out the

    > manual high limit sensor ,i cannot remenber if

    > it's a resistor or klickon type sensor if the

    > latter jump it out and see what happens ,did you

    > also chk the board fuse ,i also never let

    > electricain wire my boiler if they insist (cause

    > they want to hammer the GC or HO)then i let them

    > know that they will be totally responable for all

    > cost assscoted with repair then they usually then

    > back off .Also just go over all low voltage

    > wiring to make sure that he is not powering zone

    > valves or any other low voltge off the tt

    > connections on theboiler .In all cases that i

    > have experenced with f00 code where all asscoted

    > with the fact no one programed the post circ

    > times as stated before the foo code is usually

    > always assocated with manual reset hi limit also

    > don't rule out that the sensor may be bad causing

    > the unit right at start up to go through it

    > normal fan pre purge before coding f00 peace and

    > good luck hope i helped clammy


    There was an error rendering this rich post.

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