Pilot light blowing out on old gravity furnace

Erin

Hi---I searched the archives a bit but am way out of my league. Bought a house built in 1923 with the original furnace and it's one of those monster octopus gravity ones. Gravity air, not radiators. In the last month the pilot light has gone out four times. It does have what I think is called a thermocoupler attached in front so the gas isn't building up when the pilot's out, but in Minneapolis we could have some disasterous results pretty quickly without heat! Any thoughts? How inefficient are we talking about here too? Oh, and can the ducts be cleaned? There's no filter on this furnace. Its ducts are all asbestos so I'm thinking it would be very expensive to replace and so far it's worked like a charm. When it's working, of course... Thanks for any expertise!

John Mills_3

Ready for the Smithsonian!

It's either a thermocouple (used on a 24 volt gas valve) or a thermopile which generates enough voltage that house current isn't needed on the system. Could be a bad thermocouple or thermopile or a dirty pilot burner. Either should have a tech look at as well as do a safety inspection to make sure the heat exchanger is sound.

If sound, hang on to it IF you can afford the gas bills and don't mind not having A/C. No real filtration possible. It might be wise to have the ducts cleaned.

As for efficiency, probably in the 45-50% range over the course of the winter. LOTS of loss up the chimney during the off cycle. Friend in your fair city had one. Keeping the house cool his bills were much higher than neighbor in similar house with 80% furnace who kept it toasty. He's since gone 80% himself, haven't asked what the bills did. He's enjoying A/C!