Changing a thermostat

[wodger]

Hi,

I have purchased a new Honeywell digital room stat to replace an old Drayton one. I am not 100% sure about changing the wiring though and was hoping someone on here might be able to help?

The first image is the current stat wiring diagram. I have wires connected to points 1, 2 & 4 which all go back to the boiler. There is nothing connected to 3.

The second two pictures are of the new stat and its wiring diagrams. I am thinking I need to map the wiring as follows:

Drayton > Honeywell
1 > A
2 > C
4 > B

Can anyone confirm if this is correct?

Much appreciated,
Warren

Current Stat

New Stat

 

[jackthom]

Connect the permanent Live wire (1) to the Honeywell A

The switched live (2) goes to B



The Neutral wire (4) will no longet be required, I am assuming this model is a battery powered room thermostat.
Definitely DO NOT connect neutral to C or you'll need a new thermostat.

 

[matt1e]

No you need

1 = A
2 = b

and the other wire (probably blue or grey) is unused so put it on a connector block to make it safe

matt

 

[matt1e]

oops jack beat me to it

 

[wodger]

Thanks for the quick reponse. Knew I could count on this forum to help me out.

Out of interest what is the purpose of wire 4 (blue as you correctly pointed out) on the current stat if it is not required on the new battery powered stat?

 

[jackthom]

The neutral (and Live) got switched across a very small heating element inside the room thermostat. This helped it keep up with the increasing room temperatue while the heating was ON, so the thermostat could react quickly when the temp rose to the target level without the room temp overshooting too much.

The modern digital units have a smaller sensor which naturally adjusts quickly to a change in temperature.

 

[wodger]

Thanks very much. Makes sense now.

Regards
Warren