Hi i am trying to wire the receiver of the honeywell cmt921 to my worcester 28i, but the wiring diagram do not seem to be clear, please can someone tell me how this has to be wired? thanks.
honeywell cmt921 to worcester 28i
- Thread starter robinson1986
- Start date
Sponsored Links
Wire as follows:
CM921 ........ Boiler
L ................. Ls
N ................. Ns
A link to terminal L of CM921
B ................. Lr
Remove any link between Ls and Lr
CM921 ........ Boiler
L ................. Ls
N ................. Ns
A link to terminal L of CM921
B ................. Lr
Remove any link between Ls and Lr
and the feed to the receiver from the spur as well as to the boiler ?
The boiler always needs a feed from the spur to the L and N terminals.
You can either feed the receiver from the boiler (Ls to L and Ns to N), as I have shown, or you can fed it direct from the spur; it just depends which is more convenient.
In both cases you need the link from L to A at the receiver and a wire from B to Lr.
Sponsored Links
cheers, however im 99% certain i tried that method,and it still wouldnt work, the receiver lights up when the programmer is switched on to manual or the when timer kicks in but it doesnt start the boiler up ??
Do you have a multimeter?
If so, check the voltage between A and N of the receiver; it should be 240V AC. If not, check there is a link between L (either one) and A.
If you have 240V at A, check between B and N when the green light is on; it should be 240V AC.
If that is OK, check that you have 240V between N and Lr at the boiler. If not, the wire from relay to boiler is faulty.
ok will check tomorrow night when im next at the house, how can i check the voltage on the reciever without the front on though? as the front has the circuit board built in?
You can check the voltage between L & N and between A & N with the front removed. It's only the voltage between B & N which is the problem as the terminals can only be accessed when the front is off.
You could connect short lengths of wire to B & N which comes outside the box and attach your meter to them. But be very careful as the wire from B should be live when the relay is on.
Just like to say thanks for your help, it ended up being a damaged core in the flex. no idea how that happened as its a first that i know about from a core(blue) to break...strange, anyway boiler is up and running, thanks again for your help/guidance.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
