Thermostat Basic Theory

[TimReal]

I've just added a new programmer to our gravity hot water, pumped heating system as the old one had died. New programmer is a Horstmann Centaurplus C27. This works fine as I just used the same scheme of wiring as to the old unit.

I'm now wanting to add a room thermostat (no existing one) and I've bought a Horstmann Centaurstat 7 to do that.

Before I get onto the specific "which wire goes to which terminal" questions I need help on the basic theory.

Obviously my new programmer is the only thing connected to the boiler and pump. Is the thermostat wired as an extension of the programmer, so I connect wires from the programmer straight to the thermostat? Or is the thermostat wired directly to the pump (and/or boiler), bypassing the programmer all together?

Hope this makes sense

 

[jackthom]

The programmer supplies a mains voltage on a wire to the pump/boiler when the heating is supposed to be on.

In a basic system a room thermostat simply acts as an extra switch and is placed in this wire between programmer and pump/boiler.

When the room has reached the desired temp. this switch goes off and cuts off the programmer signal to the pump etc.

 

[TimReal]

Hmmm, not quite how I thought it would be, but thanks for your reply.

 

[jackthom]

Hmmm, not quite how I thought it would be, but thanks for your reply.

Sorry I was keeping it fairly general for a basic thermostat.

I see that the new thermostat is a programmable one so for heating it can be wired to directly control the boiler, completely independently of the programmer.