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Nuisance Shutdowns

Noticed recently that boiler was making a high pitched buzzing so went downstairs to check on it. Wasn’t running but I verified with my DMM that there was a call for heat. Must have just shut off because I could still hear her boiling away.

Our steam system controls are so basic, (see attached photo for how my Utica PEG150 is wired) so I systematically tested each safety control to determine if one of those were the culprit. Jumpered tstat, pressuretrol, both rollout and damper limit switches. Restart system and it runs for a decent time (>10 minutes) then shuts off. Commence high pitched buzzing emanating from the ignition control module (UT 1003-620A).

I started to dig into the inputs to the control module. Confirmed 24VAC input, which confirms that the safety controls are not to blame in this instance (if one of them tripped, I wouldn’t be reading input
Voltage at the control module. Next I checked the gas valve wiring and there was no voltage to the pilot or main valve wires. Ok where next..... thinking igniter now... what else is left? Found the really good guide from this site on troubleshooting ignition modules and carried out it’s checks. All seems nominal except for the microamps. I’ve got a single rod igniter so I believe the flame sense is conducted through ground back to then control module. I measured the microamp current in series from the pilot tube to the “burner” ground wire attached to the gas valve (see green circle in picture) and get a really large value. Guide says it’s supposed to be very low, say 2-10 microamps when pilot is lit, however I’m getting much larger values around 500 microamps. Do some more digging around, I trace the source of current to the 24VAC Return wire attached to the ignition control module (see red circle in picture).

At a standstill now, can’t really confirm the flame rectification. I did order a new ignition control module - the Honeywell S8610U3009 since it does have some LEDs for troubleshooting faults. I figure it would be easy enough to slap a new one in there and confirm whether the condition still persists.

Big thanks to Ryan @NewEnglandSteamWorks for helping me troubleshoot this problem real-time via email. I’m on his “to do” list so whenever he can get out, he’ll have his shot at this one. Until then.... anyone have a suggestion?


  • ethicalpaul
    ethicalpaul Member Posts: 5,611
    Mine failed last year on my Utica. I don’t recommend it but I jumped the main valve periodically to keep some heat while I waited for a replacement. Mine failed in a way that it would light the pilot, and sense it but then it wouldn’t send charge to the MV
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • BobC
    BobC Member Posts: 5,473
    It looks like they use a molex connector for the millivolt system. Molex connectors are not the best choice for very low voltage applications. Thry unplugging that connector a few times to get rid of any oxidation on the connector pins.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge