In sci.electronics.repair, Peter W. wrote:
e) If it is an old octopus furnace (obsolete in the 1930s, much less
the 60s) as above, it will work as always as it does not depend on
line-level power.

The gravity furnace[*] in my San Francisco house is much newer than the
1930s. From memory the nameplate is mid 1960s. I suspect -- this would
fall under "happened long before I lived here" -- that the building had
a gravity furnace installed when originally built (1906), or shortly
thereafter, and in the 1960s someone decided to replace the furnace but
didn't want to reduct, so just put in another gravity furnace.

I seriously dislike it, the lack of forced air means you can't have
filters, and the lack of filters means it smells of decades of
accumulated dust every time it is turned on. I think we ended up using
it only one or two days in the calendar year of 2020. It works, although
slowly, when we do turn it on, but mostly we find other ways to keep
warm.

The ducts are all asbestos insulated, so tearing it out won't be fun,
when the time comes. The thermostat is is one of the old mercury switch
types, probably installed at about the same time. Mercury switches are
fun.

Elijah
------[*] "octopus furnace" is a slangy name for "gravity furnance"