"Jack Benimble" wrote in message
...
I have a 2-wire, 24v, single-stage heat only, SlantFin hot water
boiler, about 20 or 30 years old, maybe more. Two wires go from the
system to the thermostat in my living room. One wire is red and one
is white. On my current thermostat, the red wire connects to Rh and
the white wire connects to W1.

I bought a new programmable thermostat. It wants me to connect the
red wire to RH and the white wire to W2 (there is no W1), but also
calls for a common wire, which I don't have.

Installed with just the 2 wires, the thermostat keeps making a
clicking or chattering sound when the heat comes on. The sound
diminishes over time, but not completely. In the first minute or so,
it goes from loud clicking to a soft chattering sound that is much
lower in volume.

Jack


Maybe it is just the sound of water boiling in the water boiler?