Changing room thermostat for WiFi

[Boatman128]

A simple question. Can I replace my existing Honeywell T6360B wired thermostat with the Honeywell CM721 or 921 WiFi model.

The reason for doing this is to relocate with minimum disruption.

My existing stat has three wires. Will I only need to use two of them when I wire the receiver.

My boiler is a Potterton Kingfisher RS60 model

 

[Dan Robinson]

It is easy but you can't use the existing 3 wires.

Put the receiver box in the airing cupboard and disconnect the wire running off to the old stat.

 

[Boatman128]

Many thanks Dan. I understand that the existing wiring will be redundant, my query was regarding the wiring. Do I now only use two wires for switching at the. Receiver, that's apart from the 240volt supply, and ignore the third wire.

 

[Dan Robinson]

You need 3 wires and an earth.

Live, Neutral, switched live and the redundant earth that needs to be left for safety.

 

[Boatman128]

Thank you for the information.

 

[Boatman128]

Sorry to be a pain, but the existing wiring is three wire and earth. Is it not possible to use the existing wire and just move the wires around in the connection box next to the boiler, and then I can site the RF receiver in place of the existing thermostat.

 

[Dan Robinson]

If it is 3+e then yes.

Live and neutral (1 & 2 on your old thermostat) to L (left of the 2) and N.

Link the right L to A and then the wire on 3 goes to B.

Then simply leave your current programmer on constant for heating, or move the heating on wire to a permanent live.

Leave the earth wire tuck up safely inside the receiver box with a line connector on the end.

 

[Boatman128]

Looking at the diagram for the RF receiver. It looks like the same wiring, regardless of direct boiler or zone valve. Is my thinking right.

 

[Dan Robinson]

Yes.

My description should see you right though.

 

[Boatman128]

My existing live wire comes from a terminal black marked "CHO" and this is controlled by the programmer. Could it not say in that position.

If I put the wire as suggested into a live feet, or place the system on constant for heating, will this not leave the heating on 24 hours a day.

 

[Dan Robinson]

The cm92x is programmable. So the existing programmer is not needed for heating.

You need to power the bdr all the time.

Hence either leaving the heating on constantly or moving the wire.

 

[Boatman128]

Understand now. Is the cm92x the same as the cm721

 

[Dan Robinson]

CM921 and 927 are their premium product.

The cm7 series is their contract range with fewer features and only 4 periods rather than 6.

 

[Boatman128]

Do happen to know the difference between the CM921 and the CMT921

 

[Dan Robinson]

There isn't. CMT is just the full prefix.