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Help needed on flame rollout switch keeping tripping

njmannjman Member Posts: 8
I have an over12 year old Weil-Mclain HE Series 3 gas boiler for my baseboard heating system. Recently I noticed it is keeping tripping whenever the water temperature reaches the high limit, which shut down the blower motor then close the pressure switch followed with gas valve closed. Just after the gas valve is closed I noticed the flame from the residual gas out of the jets in the burner rolls out of the combustion chamber and into the controller chamber, at the bottom of which the gas jets reside, and this flame gets the rollout switch tripping. Anything wrong? How to get it fixed?


  • JStarJStar Member Posts: 2,752
    Roll Out

    Could be a leaking gas control valve. It's supposed to shut off completely. Maybe it's allowing a little bit of gas through upon closing. Do you smell gas after it's off?
  • njmannjman Member Posts: 8
    Yes, I do smell a little gas when it shut down.

    Yes, I thought maybe the valve close is a little delay, and it could be actually the gas leak before it is fully closed. I will replace the valve to see if it address the issue. Thanks.
  • icesailoricesailor Member Posts: 7,265
    Draft blower fan:

    I thought that the fan was supposed to run until after the gas valve closed? What's with it stopping before the flame stops and the gas valve closes?

    I haven't worked on a HE in a while but I don't remember the fan stopping before the gas was shut off. Does it have a brain? You can't screw that up easily but if wired individually, sounds like maybe the fan motor and gas valve are crossed. If that's possible,
  • njmannjman Member Posts: 8
    No other fan other than the blower

    I do not seem seeing additional fan other than the blower in the manual (the 1st PDF attachment) and on the actual boiler. The blower is connected in series with the high limit switch for water temperature then powered through a relay. My understanding is that when the water temperature reaches the set limit and limit switch opens, then the pressure switch closes and disconnect the 24V power to the ignition control, which close the gas valve, however the circulator stays on. When the water temperature drops to certain level, the high limit switch closes to allow the blower kicks in, then pressure switch opens to allow the 24V power add via the rollout switch to the ignition controller and restart the whole process. But if the rollout switch was blown off, and the ignition process will stop. On the other hand as described in Page 5 of the 2nd PDF attachment if the thermostat temperature is reached before the high limit switch, both blower and circulator will be shut off via the relay, then the pressure switch will disconnect the power to the controller, which shut off the gas valve. At either case it seems the blower is shut off before the gas valve.
  • njmannjman Member Posts: 8
    Gas valve

    Could the gas valve be fixed instead of replaced in whole?
  • unclejohnunclejohn Member Posts: 1,689
    Seems Like

    The pressure switch is sticking and not opening when the blower shuts off, hence the roll out.
  • njmannjman Member Posts: 8
    How to confirm?

    Any suggestion on how to test it for diagnostics?
  • icesailoricesailor Member Posts: 7,265
    Understanding Sequences:

    You gave the answer to your question. If you don't know how, or have the equipment, you need to have a professional with the equipment and parts to do the repair. Something is screwed up. You don't want to make it worse. The rollout switch is doing its job. Because something else is wrong. It didn't do it when it was new.

    I once worked on one of those. I shut it down for repairs on a Friday.. left it off for the weekend. I finished on Monday and it wouldn't start. After some consternation, I discovered that over the weekend, a mouse climbed on top of the boiler to keep warm. He chewed sections of the rubber tubes for the fan proving switch.

    I doubt that there is a way that any of us here could explain to you how to check if a mouse had been up to mischief.

    "It was running when I shut it off on Friday, and Monday it won't run, what changed?"  Something did.
  • Tim McElwainTim McElwain Member Posts: 4,436
    With the HE and VHE boilers

    there is a flap between the transition (RED Hose) and the flue collector (WHITE Hose). If that flap is not working the pressure switch will not work properly and you will get poor combustion due to restriction caused by the flap. It needs the top removed from the flue collector and a cleaning and a check of the flap to see if it needs replaced. This is a very typical problem with the HE and VHE boilers with this flap. This by the way was the beginning of a design system to reclaim some of the heat lost up the flue in the flue collector. There is a copper coil in the collector which is part of the boiler system water tubing.
  • njmannjman Member Posts: 8
    Flame rollout only at the end of a cycle

    In my case I observed weak flame rollout from the combustion chamber to trip the rollout switch only when the blower motor is shut down then gas valve shut off. Are this related to this flap in flue collector as well?
  • Tim McElwainTim McElwain Member Posts: 4,436
    Yes the action of that flap

    affects the flue gas travel which in turn affects the chamber pressure and the extinction of the gas flame in time. The pressure switch works on differential pressure red hose to white hose with the flapper in between, the gas valve is directly controlled by the SPDT pressure switch making and breaking at the correct time other wise you have residual gas in the chamber with no air entrainment hence flame roll-out. The flue collector needs to be opened up and a professional who is familiar with the Weil McLain HE series to take a look at the flap.
  • njmannjman Member Posts: 8
    Flap in Weil-Mcalin HE Series 3 flue collector?


    I do not seem seeing the manual as attached has ever mentioned about the function of this flap and the assembly or part lists do not say it either. Are you sure you are talking about something modification to address some issues?
  • icesailoricesailor Member Posts: 7,265
    Inside Out:

    Is that the thing that I've seen under the cover of, Part # 450-030-392 that's located between the red and the white tubes?

    Mice like to eat that stuff that the tubes are made of.
  • njmannjman Member Posts: 8
    edited March 2014
    Rollout problem solved-Pressure switch failure

    Thanks a lot, Unclejohn. Today my new pressure switch arrived and I replaced the old one with it. The rollout problem went away with a sharp distinction of flame after blower is shut off.

    Thanks all for your contributions.
  • Tim McElwainTim McElwain Member Posts: 4,436
    In Section "B" of the troubleshooting

    manual Weil McLain part # 550-141-565/0691DCP page 6 and 7 "Checking Air Pressure Switch" under things to check one is DIRT ACCUMULATION ON FLAPPER IN TRANSITION.
  • rrwitherspoonrrwitherspoon Member Posts: 104
    I did not know you can repair gas valves
  • Empire_2Empire_2 Member Posts: 2,343
    edited December 2014
    I don't know, call me crazy, but sounds like the draft motor is failing. Could not read with understanding of the original post so that is what I think... What I gathered the motor shut's down as it reaches hi limit, but I'm not sure if that is in fact the case. If the pressure switch was the problem the given scenario would happen at random with no specific pattern. Let's see if it pops up again after the pressure switch replacement. In addition if I am reading it right possible HX either plugged or getting plugged. Sorry could not be more decisive with what I was reading.


    Mike T.
  • Empire_2Empire_2 Member Posts: 2,343
    Just a side thought,......I would almost bet dinner that the HX has an issue of being partially plugged. "No sea food",....Maybe McDonalds.... :)

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