Room Thermostat

[FoxyChris]

Hello,

My dad currently has a Honeywell T40 dial thermostat that is now in the wrong location due to a house extension.

The plan is to change it for a Horstmann HRT4-ZW wireless one so he can pick where he wants it to go. I thought it would be a simple changeover but the old Honeywell has 3 wires. I think the wiring for this is red (1) is live, blue (2) neutral and yellow (3) switched live.

So the wires for the new unit stay as L and N as per the instructions. But where does yellow wire go? The diagram on page 6 may suggest that the yellow wire goes to pin 4 and then bridge a wire between L and Comm?
The link for the Horstmann is below.
http://www.horstmann.co.uk/downloads/ElectronicDocuments/Central-Heating/HRT4-ZWweb.pdf[/img]

 

[Whitespirit66]

You can't wire the stat's receiver in old stat's location using existing wires. You need to put receiver near boiler or ch wiring centre to get permanent 230v supply that's not available at old stat's location.

Then you need to remove red wire from wherever it connects at boiler/wiring centre and put a wire from Horstmann term 2 to where you just removed red from.

Same with yellow wire, remove and connect wire from H/mann term 4 to where yellow wire came out. Remove the blue/neutral as not needed.

If in doubt, you need plumber/heating eng.

 

[FoxyChris]

But i tested the red and it's a permanent live so why can't I use this for the new receiver?

 

[Whitespirit66]

But i tested the red and it's a permanent live so why can't I use this for the new receiver?

What boiler and system do you have? Was the red live with heating turned off at programer/timer?

If you do have a permanent live and only 3 wires at stat, you could connect red and blue to Horstmann's L and N. Then link L to 2 and connect yellow to 4.

If no permanent live, easier to wire in at boiler/wiring centre.

 

[FoxyChris]

Thanks for the quick reply your suggestion is what I thought I could do. The red is a permanent live and when you click the thermostat to on it send the power down the switched live to the boiler. I can just bridge the live wires like you say and connect yellow to number 4