On 4/29/2011 9:40 PM, Stormin Mormon wrote:
Backwards. The heating system doesn't provide a common.


OK, I don't understand the most elementary things about electricity.
The way I imagined (in my amateur mind) things working is like this:

The boiler is connected to the thermostat by two wires. It powers one of
the wires (at 24V, 60hz), but the circuit is not closed. When the
thermostat needs the boiler to turn on, it closes the circuit. The
boiler senses that the current is on and turns on. Is that not the right
sketch?