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Prepurge cycle during thunderstorm

Since having a boiler replacement using a Peerless oil boiler and Riello 40 burner in 2019, I have encounter a strange issue that the technician is not able to resolve and has replaced many parts (flame sensor, switching relay, and hydrostat). Each time a thunderstorm occurs the boiler will enter a prepurge stage for approx 2 seconds (not the typical 10 seconds) without igniting. This cycle will continue sprodaically until the thunderstorm has passed, afterwards it will operate normally. There is no call for heat at the time it occurs. I call it my demonic boiler as it only occurs during thunderstorms which are becoming much more frequent in my area. It does not appear to be related to any electrical disturbance (no other electrical issues). I think it is related to a change in atmospheric pressure during the storm?


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,171
    edited July 2023
    One of the many reasons that I do not like the HydroStat boiler control and why I prefer the L7224 from Resido (formerly Honeywell). Ask @HVACNUT about the HydroStat control that he likes so much.

    I don't believe that it has anything to do with the Riello Burner or the Riello burner control. That control actually solved a "Strange Electric" issue for one of my customers. Read this comment from a few years ago. https://forum.heatinghelp.com/discussion/comment/1651498#Comment_1651498

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • 109A_5
    109A_5 Member Posts: 1,388
    hello @kvieten,

    I don't know what in that setup would be susceptible to atmospheric pressure changes. Hydrolevel does have a grounding bulletin. I think the common issue was from interference from the igniter. I wondering if the wires to the TT terminals are being tickled by some sort of static electricity or lightning during the storm. Thermostat wires can act like antennas. If you jumper the TT terminals for just a second (or less) does the prepurge act the same ?


    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System