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Wiring Combi to RF Stat

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Nat

Hello all,

A little bit of help please...

I am trying to wire a Honeywell CMT 927 wireless room stat to a an old Worcester 24I combi boiler.

The heating is currently controlled by a mechanical timeclock in the fascia of the boiler with three wires going into CN, CI and CL terminals on the boiler. The boiler is connected to L, N and E via a fused plug.

The boiler has the following terminals:

L, N and E CN CI CL RN RI RL

I think RI and RL are linked over.

The receiver has the following connections N,L,L and A,B,C

The wiring diagram doesn't make any sense to me as it T1 and T2 on it.

I don't suppose anyone has a wiring diagram to help me out on this one or could point me in the right direction?

Many thanks,

Nat
 
haha had this other week to be honest as diagram for this isn't overly clever !

you tube it and shows exact how to wire and set model up !!
 
funny enough, I have watched that video some weeks ago but forgot about it :D, silly Billy
 
You need a four core (plus earth) heat resistant cable.

Connect as follows:

Boiler - CM927

CL - L (brown)
CN - N (blue)
RL - A (colour 3)
RI - B (colour 4)

The built in clock should be disconnected (preferable) or set to permanently ON.
 
doitmyself said:
You need a four core (plus earth) heat resistant cable.

Connect as follows:

Boiler - CM927

CL - L (brown)
CN - N (blue)
RL - A (colour 3)
RI - B (colour 4)

The built in clock should be disconnected (preferable) or set to permanently ON.
Click to expand...

Thanks doitmyself - very helpful.

So I don't need to bridge from L and N connections in the boiler to L and N in the receiver? I just connect CL in the boiler to L in the receiver and CN in the boiler to N in the receiver? Disconnect the timeclock and remove the link over from RI to RL?
 
Are the terminal blocks marked X1 and X2? Is it the 24i Junior/RSF?
 
M.Joshi said:
Are the terminal blocks marked X1 and X2? Is it the 24i Junior/RSF?
Click to expand...

No. Have a look at the original post where I have listed the terminals. This is an old Worcester 24I not the modern one.

Cheers
 
just phone up boiler manufacturer they will tell you exactly what you need to do , had same prob with same stat few weeks back , plenty of helpfull replies on here but also as many difference of opinions which just confused everything .
 
I really like the stats, but the first time I fitted one it wasn't overly clear and the diagrams they provide you with arent the best.
 
Nat said:
So I don't need to bridge from L and N connections in the boiler to L and N in the receiver? I just connect CL in the boiler to L in the receiver and CN in the boiler to N in the receiver?
Click to expand...
CL is effectively the same as L and CN the same as N. They are just there to power the clock. So you might as well use them to power the receiver.

Disconnect the timeclock and remove the link over from RI to RL?
Click to expand...
Woops! I forgot to say that you need to remove the link connecting RI to RL. If you don't the boiler will continuously 24/7!! 'A' connects to RL and 'B' to RI.
 
Last edited:
Leave the link in from R1 to RL as in effect you are wiring what the boiler thinks is a programmer if you remove that link it will not fire up as it will think that there is no call from a roomstat.
 
Millsy 82 said:
Leave the link in from R1 to RL as in effect you are wiring what the boiler thinks is a programmer if you remove that link it will not fire up as it will think that there is no call from a roomstat.
Click to expand...
That's correct if you are connecting link L to A on the relay and connect B to CI.

You can also do it the way I suggested. However I omitted to say that you then need to link CL to CI.

Which ever switched live you use, CI or RI, the other one has to be linked to its adjacent CL or RL.
 
Right I get what you mean now I think that is an overly complicated way of doing it myself but if it works correctly it works I suppose.
 
Thanks all for your replies.

Seems there are different ways of doing it but if I go with doitmyself this is what I do:

1-disconnect timeclock
2-move link over from RI/RL to CI/CL
3-connect CN to N in receiver
4-connect CL to L in receiver
5-connect RI to B
6-connect RL to A

Is that right, doitmyself?
 
CL - Live
CN - Neutral
Link between live and A
CI - B

Theres not alot in it but that would be the way that I would do it as then all the wires come off and go back to the same part of the PCB
 
As you said in post 18, remove the existing timeclock:

You need to bridge CI & CL. No link across RI and & RL.

Take the supply for the thermostat receiver from CL and CN.

RL to A on the receiver
RI to B on the receiver

What I meant earlier was that the terminal block with all those connections is X2.
 
Nat said:
Thanks M. Joshi. Very kind of you to go to the trouble
Click to expand...

No problem - one thing I should have made clearer is that the link across 2 & 3 is what you will link across CI & CL on the terminal block.
 
Last edited by a moderator:
Many thanks to those who replied. Did this job this morning and all went well. Easy when you know how!
 
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