Room temp. Control vaillant boiler fix?
- Thread starter Sahib
- Start date
The CM901 and CM907 are programmable thermostats
Your confused.
The rectangle in the diagram around "CM900" and "A,B,C" represents the thermostat and the relay inside. The relay connects A to B (heating system) or A to C (cooling system). The diagram shows A connected to C.
It doesn't really matter, but it's preferable if the brown connects to A and blue (with brown sleeve each end to show it's the switched live) to B.
A should connect to terminal 3 on the boiler and B to terminal 4. Nothing needs to be connected to terminal 5.
Terminals A and B on the CM900 do indeed provide the switching facility. Do not connect anything to C. The drawing you posted shows that clearly.
Both A and B will be 'Live'. Therefore both should have brown conductors. This is usually achieved by adding a brown sleeve to the blue wire. The drawing here is of a lighting circuit, so don't get hung up on the details, my purpose in showing it is so you can see the brown sleeve on one of the blue wires.
Then the two brown switch wires connect to the appropriate terminals at your boiler, both of which will also be 'live' and can be identified from the wiring diagrams in your boiler manual.
But as I said before, if you can't understand the drawings, it would be better if you didn't attempt it.
Both A and B will be 'Live'. Therefore both should have brown conductors. This is usually achieved by adding a brown sleeve to the blue wire. The drawing here is of a lighting circuit, so don't get hung up on the details, my purpose in showing it is so you can see the brown sleeve on one of the blue wires.
Then the two brown switch wires connect to the appropriate terminals at your boiler, both of which will also be 'live' and can be identified from the wiring diagrams in your boiler manual.
But as I said before, if you can't understand the drawings, it would be better if you didn't attempt it.