Replacing Drayton programmer with THR870CUK thermostat

[theinnertemple]

Hi,
We have no room thermostat in our house only thermostatic rad valves which is costing us a fortune. I thought I could therefore replace our Drayton timer (Badged as a British Gas UT1) with the Honeywell Homexpert THR870CUK. The Drayton runs the heating on a Baxi combi boiler. However the Drayton has 4 wires coming in; L and N to terminals L and N and live and live return to terminals 1 and 3, respectively.

I am assuming that the first pair simply power the Drayton timer unit (the Homexpert is battery powered) and the second are the ones I want so I have two questions. Firstly is the programmable thermostat suitable for replacing my timer. Secondly am I right in thinking that I just need to make safe the L N cable and wire in the Live and live return into the new unit or will this affect my hot water?

Any help most gratefully received.
Tom

 

[twgas]

Secondly am I right in thinking that I just need to make safe the L N cable and wire in the Live and live return into the new unit or will this affect my hot water?

Thats about it but depending on the location you may do better with an RF model

 

[theinnertemple]

Thanks Mike,

I'll give that a go then. What advantage does the RF model have?

 

[twgas]

The transmitter part is the prog/stat so can be fitted in an appropriate location and the receiver is fitted where your timer now is, which is, more often than not, next to the boiler in the kitchen or some other unsuitable spot.

 

[theinnertemple]

Thanks again. I realised what you meant as soon as I hit post.

One advantage of living in a modern open plan shoebox is that the timer controls are in the living room/dining room area so that's not a problem.

On a related note I have traced back the mains supply to the timer and isolated it but noticed when the timer is not connected the hot water isn't coming on.

I'm assuming this is because the timer has some circuit in it which allows the boiler to heat the water even when the heating is off. Will this be the case with the thermostat do you think?