Ancient Honeywell Room Stat

[Jim]

It is brown with a grey cover plate. Two wires -red to Terminal 1 Neutral to Terminal 3. Earth wire cut back. I get a reading of 12v.
I have found 4 sets of numbers 4200.3879.001(cover Plate)
4200 3840-00(On wallplate)
and inside the stat 42003878.
No joy in establishing replacement spare from suppliers and Honeywell very busy.
The thermostat is not functioning properly. Any advice please on a simple product replacement.
Thanks
Jim

 

[ChrisR]

WIth only 2 wires to use , no neutral for the anticipator, I'd suggest an electronic one for a narrow hysteresis or "dead band".
You could get a way with a cheaper one such as this, which still recommends the extra connection:
http://www.screwfix.com/prods/22657/Plumbing/Central-Heating-Controls/Danfoss-RMT230-Room-Thermostat

 

[imroberts]

I imagine you could replace this with the Honeywell DT200

 

[D_Hailsham]

It is brown with a grey cover plate. Two wires -red to Terminal 1 Neutral to Terminal 3. Earth wire cut back. I get a reading of 12v

It's a Honeywell T6160B!

The blue is NOT a neutral, it's the switched live.

If you use the DT200 suggested, the wiring is:

Red to Terminal A (power from the time switch)
Blue to Terminal B (power to boiler etc)
Earth not required

The blue wire should really have some red sleeving or insulating tape wrapped round both ends to show it is a switched live.