Honeywell CMT921 room stat

[D_Hailsham]

the model numbers are V4043H1106 for the airing cupboard one and 272848 for the ones in the loft.

OK, they are normally closed zone valves with an auxiliary switch. When you apply voltage to the brown and blue wires the valve opens and the auxiliary switch closes, connecting the grey and orange wires. The grey is usually connected to a permanent 240 supply; the orange goes to the boiler switched live terminal.

Edit: Some version of this valve have a white wire as well. This is not used in your set-up.

However we still have the strange problem with your voltages on the thermostat. I haven't worked out what is happening yet; will get back to you.

 

[D_Hailsham]

I think I am there.

I say anything else I want to say what the connections are in this newly found junction box (JB), as there seems to me to be something wrong
Stat R - ZV grey
Stat Y - ZV brown
Stat B - not connected to anything at all

That means Stat R is the supply from the programmer CH ON terminal and Stat Y is the switched supply to the valve. Unusual, but OK. The normal method is to connect the grey wire to a permanent supply terminal in the junction box.

Do you mean the stat B is not connected at the junction box?
If so we can make use of it.

Disconnect the Satchewell stat

Connect stat R wire to receiver L
Connect stat Y wire to receiver B
Connect stat B to receiver N
Link receiver L and A

At the junction box, connect the disconnected stat B wire to a neutral point, e.g same as blue from the zone valves.

 

[matt1e]

I think I am there.

I say anything else I want to say what the connections are in this newly found junction box (JB), as there seems to me to be something wrong
Stat R - ZV grey
Stat Y - ZV brown
Stat B - not connected to anything at all

That means Stat R is the supply from the programmer CH ON terminal and Stat Y is the switched supply to the valve. Unusual, but OK. The normal method is to connect the grey wire to a permanent supply terminal in the junction box.

Do you mean the stat B is not connected at the junction box?
If so we can make use of it.

Disconnect the Satchewell stat

Connect stat R wire to receiver L
Connect stat Y wire to receiver B
Connect stat B to receiver N
Link receiver L and A

At the junction box, connect the disconnected stat B wire to a neutral point, e.g same as blue from the zone valves.

I think you are there too mr hailsham just worked it out this way too but never noticed the second page so you beat me!
but i will concur

In case you are wondering denvillesman the strange voltage readings are due to the coil of the motor in the zone valve being connected to neutral (which is why the yellow seemed like a neutral)

matt

 

[denvillesman]

Well, D Hailsham (I guess Derek or Dave?), it took a little while, but as I have said already I admire your patience, particularly with the innocents such as myself. YES it is all working fine with the final wiring instructions.

I suppose with the glory of hindsight it was quite straightforward in the end when we had established the wiring went to a ZV. But I daren't think I could have done it without you. Thank you so much.

And nice to see that A N Other in the form of Matt1e was clearly keeping an eye on the string, thanks for the final observation on the voltages.

Bizarrly now, because of the mild weather I shall have to wait a while before having the fun of playing with the toy from the comfort of my sofa.