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Stack temp switch in 1958 era oil furnace, FHW--- expected life?
Working fine , but since it's so old I started to wonder how long these things last.
And if they typically fail in a way that they don't shut down burner if no-fire.
It's original equipment, so no newer than 1958. Old sunbeam oil furnace, FHW and domstic hot water. Currently firing at ~ 1.1 GPH, IIRC think boiler is rated for ~ 180kBTU ball park
It's a Honeywell Type R986A ,Minneapolis-Honeywell Regulator Co
About 1 foot long spiral bi-metal? spring in exhaust flow after heat exchanger.
Contains low voltage transformer. power relay, time delay( likely thermal)
Was considering designing in a cadium cell flame sensor for no-fire safty redundency.