DIY Doctor UK DIY Forums

Posted: **Thu Feb 19, 2009 9:20 pm**

i have a worcester 28cdi combi boiler with its own timer built into it would it be possible to fit a Honeywell CMT921 wirless thermostat to it and how would it affect the built in timer

Posted: **Thu Feb 19, 2009 11:45 pm**

It is possible to fit a thermostat with almost any type of boiler. Where yours also has a built in timer means that they will run in conjunction with each other. In other words, the boiler will not fire up until both the timer is on and the stat is calling for heat.

The worcester will have internal connection points specifically for this type of installation.

Posted: **Fri Feb 20, 2009 2:29 pm**

It is possible, as it's just the same as fitting a standard hard-wired room stat. The stat and timer will work together, the timer bringing the boiler on at set timkes and the stat regulating the temperature of the room you fit the stat in.

Check your wiring diagram for the boiler, it will be in the manufacturers instructions and possibly on the inside of the boiler cover. It will show the room stat connections, this is where you connect the receiver, you also need to connect into the fused spur.

htg