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Boiler shutting off before reaching temp

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AlwaysLearning2024
AlwaysLearning2024 Member Posts: 114
in THE MAIN WALL

Hi Everyone,

noticing a new issue with my WM cg-8 boiler. Reverse return hydronic with fin tube.

The boiler starts and runs just fine yet once the temp hits roughly 155 degrees, the boiler shuts off, flue dampener closes. Even though the Delmar 256 says keep going. And then doesn’t fire again until the temp drops to around 130.


the tekmar 256 shows “fire” during this shut off time, yet the boiler doesn’t fire.


if I manually power cycle the boiler, I can get the boiler to fire.


I’’m assuming there is some safely switch that may be tripping once 155 ish is being hit?

The high limit on the boiler itself is 180.

Pressure is good.


thanks for any help,

Comments

  • tcassano87
    tcassano87 Member Posts: 112

    Have you had a plumber come out and look at it, does it ever turn back on or does it stay off until you power cycle?

    If it turns back on but it's reaching temp your temperature probe could be reading incorrectly, need to test the OHMS and compare it to Weil-Mclains chart to see what temp it thinks the boiler is at. If thats reading correctly could also be a problem with the board

  • AlwaysLearning2024
    AlwaysLearning2024 Member Posts: 114

    thanks @tcassano87 .Tech hopefully coming out today. It does fire up without the power cycle but the temp drops before this can happen.

  • hot_rod
    hot_rod Member Posts: 27,060

    What are the boilers aquastat settings? It could be they are set low and turning off even though the tekmar is calling.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • AlwaysLearning2024
    AlwaysLearning2024 Member Posts: 114

    Thanks @hot_rod. Just a high limit on this one which is set to 180. (510-312-250).

    The Relay buzzes a bit, too.

    Screenshot 2026-01-26 at 1.16.11 PM.png
  • HVACNUT
    HVACNUT Member Posts: 7,305

    Do you know actual supply water temperature? When the boiler shuts down and after the damper closes, jump the limit and see if it cycles back on.

    AlwaysLearning2024Sukhoi29SU
  • AlwaysLearning2024
    AlwaysLearning2024 Member Posts: 114

    @HVACNUT ! Thank you!


    I jumped the high limit and it fired right up.

    I rotated the high limit dial a few times to maybe dislodge some bits. Testing now.

    Maybe best to grab a replacement?

    Thank you!

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