How about a gravity one from 1941?
1941 Lennox. This is a very comfortable heating system. No drafts, and a nice even heat. I have no intent to replace it, even though I must use window units in the summer.
I have lived here since 1979. In all those years, I have only had to replace the transformer for the thermostat. I replaced the original stat with a programable type in 1989. That stat was upgraded to a day by day programable stat five years ago.
If you are to look close, you can see that there are two gas valves installed in the line. The original valve stuck in the open position in 1957. My grandparents owned the house then, and were away at church the Sunday the valve stuck. The furnace just kept pumping the heat out in the meantime. When my grandparents came home, the house was like a blast furnace. The varnish on the woodwork was sticky, they said! I am sure the furnace would have burned the house down, if nobody had returned home. To be on the safe side, they added an additional gas valve. That way, if one valve stuck open, the other would shut the furnace off.
I tested the valves in 2005, and found the original valve to be stuck open again. The valve that I replaced is the smaller gray valve. I do not know when the original valve stuck open for the second time. It could have been right after it was "repaired" in 1957, or a few years before I tested both valves in 2005.
At any rate, I feel safer with two working gas valves on this vintage furnace.
This pixs was taken of the fans really, the furnace was just in the background. :>
