Replacing a Satchwell TLX-2356 room thermostat with a Honeywell DT90e

[Spencer1984]

Hi all,

I'm replacing an old Satchwell (or Sunvic) TLX 2356 mechanical room stat as it only "clicks" on above 25C.

New stat is a battery powered digital Honeywell DT90e.

TLX wiring as follows (as I understand it):

Terminal 1: Demand (or "Switched Live") - Yellow
Terminal 2: Satisfied - Brown
Terminal 3: Common - Red
Terminal 4: Neutral - Blue

Am I right to wire the new Honeywell stat as follows:

Terminal A: Common - Red
Terminal B: Demand - Yellow
Terminal C: Satisfied - Brown
Isolate and insulate Neutral - Blue

HW & CH both heated by a (very) old Vulcan Continental floor-standing boiler, circulator pump, 3-port valves, etc...on a gravity fed system.

Thanks,

Spencer

 

[flameport]

Correct, but it is very unusual to have a system which requires 'satisfied' as in the brown wire.

Is the brown wire separate, or part of the same cable as the other 3? Is it bare copper?

 

[Spencer1984]

Correct, but it is very unusual to have a system which requires 'satisfied' as in the brown wire.

Is the brown wire separate, or part of the same cable as the other 3? Is is bare copper?

The system is very old and a bit mis-matched. 13 rads in a 3-bed semi...half on 15mm, half still on microbore and I believe Vulcan actually stopped making the boiler before I was even born! So I'm not surprised the system is "unusual" in needing a satisfied line!

I'll need to double-check the satisfied to see if it's part of the same cable as the others or not. From memory, it's brown-sleeved and definitely not bare copper. I'll try and upload some pics too...

 

[Spencer1984]

Ok, so this is the old Satchwell on the wall with the dial removed to show the wiring instructions...

Plastic cover removed to expose actual wiring...

"Brown" wire is actually more black in colour and is a separate cable from the other 3 colours.


But the plot thickens! The 3 colour cable is actually a 4-wire cable, as when I've loosened the stat away from the wall, I've revealed an additional bare-copper wire which is attached to (what I presume is) an earth at the back of the thermostat...

Not a great pic, but you get the gist.

So now I'm thinking my original wiring plan was correct, but I know have to isolate and insulate the bare-copper "earth" as well the blue neutral?

 

[Echo the husky]

Yes.