We have a propane-fired hot-water baseboard heating system (with 2
zones) that we don't use all that much because of its inefficiency. (We
heat mostly with wood and kerosene.) We've only used it once or twice
Today, because it was so cold and windy, I lit the furnace to make sure
the pipes don't freeze under the house. Everything seemed to work fine
-- except that the water circulation pump for the system never shuts
The air temperature at the two thermostats (upstairs and downstairs)
was above where they should have been "calling" for heat. The furnace
was up to operating temp and pressure, with temp of 200°F and pressure
of about 22 psi, according to the gauge.
The propane burner cycles on and off, but the water circulation pump
The water return lines for both zones are hot, so it appears that both
zone valves are open.
Can anyone clue me in on why the circulation pump just runs and runs and runs?
Might it be the aquastat? Could bad/sticking zone valves cause this? (I
replaced one zone valve a few years ago, but it seems odd that both
zone valves would go bad at the same time.)
Where would you experts begin to diagnose this?
Thanks very much in advance for any advice.