A couple of months ago I asked this question regarding my natural gas furnace that is used to heat my house via baseboard/water heating.

It seemed to have quit working, but I called the repairman. The repairman spent less than 5 minutes in my home and just pointed out that there is an upside down button I can press to reset it. This consultation cost me $300.

Pressing the button works fine, except that I have to press it 5+ times per day, now that it is getting cold and snowing. I need to find a somewhat better fix, but I definitely do not have the $ for the repairman to come back.

I forget exactly how he explained it, but basically I think he said there's some cut-off in the hood that is getting mistakenly tripped. I think he suggested that the next step would be to clean, repair, or replace some part of that to prevent it from cutting off.

Given that it's cold and I don't have the money for professional repairs, is there some sort of temporary way to keep the furnace from mistakenly shutting off?

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Stack Exchange is rotating that 2nd photo on me, it seems. For more photos please see the link above.

  • @chris I couldn't agree more. It's a Sentinel SE-105 EDP. I will add photos right now.
    – Hack-R
    Jan 6, 2017 at 19:54
  • @chris thank you very much. This is all starting to make sense. I think he did say something about possible blockage and when I bought this house this passed summer they said it was missing a flue cap but I forgot about that until just now.
    – Hack-R
    Jan 6, 2017 at 20:24
  • Possibly leaves or pine needles blocking the flue.
    – user39367
    Jan 6, 2017 at 20:25

1 Answer 1


Blocked flue and/or insufficient combustion air inlets.

Charging $300 without at least giving you a complete understanding of the problem was pretty lame.

That looks like the flue rollout sensor. If that is what is tripping, then you might have a blocked flue. Verify that the damper above that opens fully when the boiler turns on. Does it? Also check the combustion vent outside and make sure there's no obstruction like a bird's nest. Turn the water heater to pilot, turn off the furnace, remove the flue cap outside and inspect it with a flashlight. The button is on the bottom of the rollout sensor I presume (I cannot really see it).

If the flue damper does not open correctly then disconnect the actuator and manually lock it in the open position. Doing that will hurt efficiency a little, but the boiler will run.

The other obvious thing to check is combustion air inlets. I see no outside air inlets in the photo. There needs to be significant airflow into the room from outside to supply combustion and flow out through the flue. If the room is sealed tightly from the outdoors then that is a problem.

  • Any thoughts on how I clean it out? Do I need to get on the root to look at the opening of the chimney or is the problem more likely at the base end?
    – Hack-R
    Jan 6, 2017 at 20:30
  • 1
    @chris copy your entire comment and paste it in your answer an answer this short will get flagged and possibly deleted but with your additional info it is a good answer.
    – Ed Beal
    Jan 6, 2017 at 20:37
  • 1
    Hard to tell from the photo inside the room. Since you have a horizontal run that appears to go outside, the blockage is likely at the elbow where it makes the transition to vertical. If you can take it apart at the elbow that is likely the easiest method. Since this flue is for gas appliances and not a solid fuel appliance it is technically called a "vent" and not a "chimney." It operates at much lower temperatures than a chimney.
    – user39367
    Jan 6, 2017 at 20:38
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    One word to the wise: By the time the flue rollout starts tripping, significant combustion products are flooding back into the room. Once this condition is severe enough, oxygen is displaced by combustion gas and the flame starts burning rich, at which point carbon monoxide is produced which could ultimately kill people in the home. Repeatedly resetting the flue rollout without correcting the problem was extremely bad advice from the Pro that Hack-R hired. Hack-R was lucky no-one was hurt.
    – user39367
    Jan 6, 2017 at 21:17
  • Hey I just wanted to say that I gave it a go this morning and I think I fixed it. Thank you so much! You saved my life. Man there was so much dirt in there. It looks like small chunks of dirty particle board board and char. Very strange.
    – Hack-R
    Jan 7, 2017 at 13:26

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