Honeywell T6 Thermostat Wiring

26 Sep 2018
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United Kingdom
Hi, I need a bit of help replacing an old Drayton RTS1 thermostat with a Honeywell T6. The Drayton has standard live, neutral and call cabling connected via relay, but the T6 expects two "Thermostat" wires and is 20V. This rules out connecting the 230V live connection. I believe the T6 receiver box will feed the 20V to the thermostat, but my problem is I only have the call wire. Will I need to install an additional wire? Has anyone had experience replacing this type of thermostat with a smart one?
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Are you trying to mount the receiver where the RTS1 is currently located? If so, that's where you are going wrong. The thermostat goes there; the receiver goes at the other end of the cable connected to the thermostat. This will depend on what system you have and how it has been wired.

Do you have a combi boiler or is there a separate hot water cylinder? Pics might help.
Thanks for replying. Managed to get it working in the end. The yellow "call" wire was going from the thermostat end to the boiler end in a terminal block. I have pinched this wire along with the red wire to make the two Thermostat connections needed. The old neutral and earth wires are now spare. I didn't realise at first that this cable was going point-to-point, thinking it was connected to the mains in some way.

Okay, I need a little more help. Comms between the thermostat and the receiver box is sorted. That bit is fine. Now my problem is at the receiver box/boiler end.

I have an Ideal Isar m30100 combi boiler. Here is a pic of the original wiring at what was a Drayton programmer next to the boiler:


This is now replaced with the Honeywell receiver box. Here is the wiring diagram from the Honeywell T6 instructions for a combi boiler:


The presence of the switched live confused me and I wired as per diagram 'A' in my previous post, however, that doesn't provide a permanent live for the boiler (which it needs) causing a problem for the hot water.

The T1 and T2 connections in the diagram, I can only assume are the two black wires in the 5 core (L, N, E, black & black) cable. Does this sound correct? Wiring as per diagram 'B' with the two black wires doesn't work either. What am I missing? Cheers.
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Another update.

Had to open the boiler cover and rewire in there! o_O

This is how I found the 5 core cable wired inside:


The two black wires going to the same place: L2 (why??)

Removed one of them and connected to L1, then connected to the receiver box as per diagram 'B' above, and it works! Call for heat from the thermostat, plus hot water on demand. All working as it should.

Anyway, I'll leave this here should someone else run into the same problem.
Good to see you have solved the problem. I was just about to post the diagram below when I saw your last post.

OOPs! Just noticed that there should be an earth link from receiver to boiler if the supply first goes to the receiver (red route).


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