My daughter's flat has a Vaillant Turbomax Plus 828E combi boiler. I want to connect a Honeywell CMT927 Programmable wireless thermostat.
The installation instructions for the thermostat's receiver show that the "N" and "L" connections on the receiver must be connected to a power supply, and the "A" and "C" connections must be connected to the "1" and "2" connectors on the combi boiler.
Turning to the Vaillant instructions, they say terminals "3" and "4" must be connected to the thermostat. So far so good (there are no "1" and "2" terminals on the Vaillant, so I simply assume that "3" and "4" should be used).
However, on testing terminals "3" and "4" on the Vaillant with a voltage tester I was surprised to find that these provide around 210v of current. My problem is this: If the receiver is already getting a power supply from the seperate connection via its "N" and "L" terminals, why should it also get 210 volts from the combi boiler. Is it not getting twice the power that it should be and won't I blow it up - or am I missing something. I would have thought that the connections from the combi boiler would have no power output whatsoever.
I would be most grateful if someone can please advise the correct connections in a simple way that I can understand.
Many thanks
The installation instructions for the thermostat's receiver show that the "N" and "L" connections on the receiver must be connected to a power supply, and the "A" and "C" connections must be connected to the "1" and "2" connectors on the combi boiler.
Turning to the Vaillant instructions, they say terminals "3" and "4" must be connected to the thermostat. So far so good (there are no "1" and "2" terminals on the Vaillant, so I simply assume that "3" and "4" should be used).
However, on testing terminals "3" and "4" on the Vaillant with a voltage tester I was surprised to find that these provide around 210v of current. My problem is this: If the receiver is already getting a power supply from the seperate connection via its "N" and "L" terminals, why should it also get 210 volts from the combi boiler. Is it not getting twice the power that it should be and won't I blow it up - or am I missing something. I would have thought that the connections from the combi boiler would have no power output whatsoever.
I would be most grateful if someone can please advise the correct connections in a simple way that I can understand.
Many thanks