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Weil Mclain Steam Boiler Won't Ignite Randomly

ZenYogi
ZenYogi Member Posts: 1
Hi everyone.
I have a Weil Mclain steam boiler that has exhibited this behavior literally since the day it was installed. I mistakenly assumed it was the thermostat that was the problem, but now that I have replaced the thermostat and the problem continues, I was finally able to capture this on video as it was happening.

Essentially, the thermostat kicks, the flue opens, the igniter starts the pilot light (I can see the pilot light turn on) but then the boiler itself times out while the ignitor continues to zzzzap, and the shutoff closes the gas. The pilot light goes out, and the unit sits in this state of limbo.

I called Weil Mclain and explained this situation to them, but they were not able to help. This problem is intermittent, and might happen once every two weeks or so, so it's very difficult to get a heating expert on site when the condition occurs, as it's random.

Would you kindly watch my video and see if you see something obvious that we can investigate? Sincerely appreciate your input, as we sometimes come home to a frozen house.

The only thing we've done to "fix" the problem is turn the thermostat off, wait 30 seconds or so, and then turn the thermostat back up. It may take a few attempts, but eventually the boiler will work again (until it doesn't).

https://www.youtube.com/watch?v=PpKuQbFOihY

Thank you very much.

Comments

  • JStar
    JStar Member Posts: 2,752
    Does the pilot actually light off? Sounds like the 24vac supply from the transformer is too weak to energize the pilot valve in the gas control valve.
  • JUGHNE
    JUGHNE Member Posts: 11,042
    Or erratic gas pressure.......pilot burner gas set too low......hit & miss ignition/light off.
  • Peter_26
    Peter_26 Member Posts: 129
    I had the same problem when the new gas valve on my boiler was installed. What model gas valve is it? Seems that the boiler is going into a "lockout" after a set amount of startup attempts. That's normal since it doesn't know if the pilot is on or not so it won't open the gas valve.

    You say the pilot does indeed light every time the boiler fails to turn on? If it does then it could be the pilot thermocouple that's dirty, not positioned correctly, intermittent or faulty. It could also be the gas valve is faulty.

    Check and see if the flame of the pilot is directly in contact with the thermocouple, it should be. Make sure the thermocouple is screwed into the gas valve securely.
  • JStar
    JStar Member Posts: 2,752
    That uses an S8610 ignition control IIRC. It's sensitive to poor grounding. If the pilot flame is actually okay, and engulfs at least a third of the flame rod, I would suspect a grounding issue, or internal fault with the module. A professional can check the strength of the pilot signal.
  • Mike282122
    Mike282122 Member Posts: 1
    Was this problem ever solved because we are experiencing the exact same thing?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,452
    Disconnect the ground wire going to the S86 ignition control with the boiler off and put a meter that reads micro amps in series with the ground wire. Turn the boiler on When the pilot lights you should read at least 1 micro amp minimum...more is better. Check the ground wire from the control to were it is grounded to make sure it is tight and scrape and clean the connections. If you don't have a meter check the ground wire and scrape and clean the connections. Remove the flame sensor and clean the flame rod with fine steel wool.

    Call a professional if your not comfortable doing this

    This is a common problem