How to investigate a faulty pilot light?

August 17, 2005 4:33 AM

What might cause a hot water boiler's pilot light to repeatedly go out? We've replaced the thermocouple, inspected the pilot assembly, and had the boiler cleaned. Twice.

Over the course of the last winter, the pilot light for our radiator boiler kept going out. At first it would only go out when the weather would suddenly shift from cold to warm. This made us suspect air pressure or down drafts. By the time Easter rolled around though, it was going off closer to every two or three days.

We've had three different HVAC guys look at it. The first told us it was the thermocouple and replaced it. A week later when it went out again, a different technician from that company told us "someone used the wrong size thermocouple."

The other two companies both wanted to start with a standard cleaning of the burner cones, etc, despite my insistence (especially the 2nd time) that the problem was somewhere else.

I'm reluctant to call any of these companies back and continue paying to not solve the problem. Is there anything I can do to check my hypothesis about wind being to blame? Are there any other likely suspects?

posted by zogbie to Home & Garden (6 answers total)

It could be a downdraft, there should be a flapper in your chimney. It could also be that there is a lack of oxygen down there, that too could be the flue-flapper backing up gasses. Make sure your furnace has plenty of room to breathe.

By the way, where do you live that you need heat after Easter?
posted by Pollomacho at 5:57 AM on August 17, 2005

I agree with Pollomacho. I experienced this a great deal this past winter. It was very windy in my area and some of the breeze was making it far enough to blow out the pilot. The maintenance company extended the fluke (I think that's what they called it - an aluminum pipe that leads down to the internal ducts from the outside) on my roof and I haven't had any trouble since...then again, it has yet to be as windy.
posted by bwilms at 6:55 AM on August 17, 2005

Response by poster: I'm in Pittsburgh. We had a pretty unusual spring this year, with some really warm days and a lot of snowy days.

bwilms, is that something a heating company could do, or do I need to call a chimney/roof person?
posted by zogbie at 8:29 AM on August 17, 2005

I think it's flue bwilms, though there is a company named Fluke that makes thermostats and electronic thermometers.

That should be something a hvac guy could work on, but I'd ask about it when making service arrangements with them.

I guess it was an early Easter this year too.
posted by Pollomacho at 8:39 AM on August 17, 2005

I once had a similar problem with high winds coming down the flue and blowing out the pilot. I fixed it (at the suggestion of the gas company) by installing a gizmo in the flue pipe called a draft diverter. It's an easy repair.
posted by Daddio at 11:39 AM on August 17, 2005

I don't know if replacing the water heater is an option for you, but if it hasn't been repaired by now, maybe it can't be fixed. If it's more than 5 years old it might be cost-effective to just start over with a brand new hot water heater.
posted by lambchop1 at 1:47 PM on August 17, 2005