Anyone changed a mechanical room thermostat to a digital one?

Jon20 · 7 Jan 2014 at 12:26

Hi, I'm thinking of changing the mechanical room thermostat in the hallway to a digital one. I was thinking of using a Honeywell DT90e http://www.screwfix.com/p/honeywell-dt90e-digital-room-thermostat-eco/41365. The accuracy seems to be getting worse on the current stat. The current stat is wired up like so:

I'm assuming:

Red - Live
Yellow - Switched live
Blue - Neutral
Yellow/green - Earth

The new stat has terminals marked A,B,C. Would live go in A and switched live in B?

The Honeywell DT90e doesn't require a neutral, so would it be safe to terminate it into a terminal block? Same with the earth as there doesn't appear to be a backbox.

Thanks.

Nightglow · 7 Jan 2014 at 12:35

Never assume anything with stats, especially wiring, mine here was a nightmare.

Google for your old stat installation guide, will show wiring configuration.

Have you considered wireless, base unit at boiler, wireless stat where ever you want it.

Got a Vaillent 824 Combi, changed timer & wired stat to a Drayton Digistat +3RF.

The Drayton should be fitted by a qualified part p electrician .

Cheaper than the Drayton,the Salus RT500 Programmable Room Thermostat is apparently very good & cheaper.

http://www.toolstation.com/shop/Hea...rmostat+Wireless+60m+Range/d230/sd2732/p10255

Jon20 · 7 Jan 2014 at 12:48

Just looked for the old stats wiring diagram (Honeywell T6360) and red is live, yellow is switched live and blue is neutral. Did consider a wireless stat but I'm not sure if the boiler could accept one and we don't have much of a problem with the stat being in the hallway. It's an Ideal Classic SE15 FF, has a Horstman programmer and tank stat as well as the room stat. Keeping the stat where it is would seem to be the easier option.

Is it ok to terminate the neutral and earth in their own terminal blocks?

Nightglow · 7 Jan 2014 at 13:01

Horstman

the newer ones might be better, but the older Diadem/Tira 425's the wiring grief I have had with them over the years :mad:

, think twice before meddling.

Just stick to a wired stat.

Jon20 · 7 Jan 2014 at 13:28

This one is a CentaurPlus C27 but I can see why you would have had grief from the older programmers, they look foul.

Nightglow · 7 Jan 2014 at 13:36

Jon20 said:
This one is a CentaurPlus C27 but I can see why you would have had grief from the older programmers, they look foul.

At least with CentaurPlus C27, it uses a standard 6 pin backplate now,so you can straight swap programmers easily between makes now.

JohnnyG · 7 Jan 2014 at 15:27

Instead of the DT90e why not go wireless with the DT92e - http://www.honeywelluk.com/products/Thermostats/Room-Thermostats/Wireless-Thermostats/DT92E/
That'll work perfectly with your 3 wire set up

Jon20 · 7 Jan 2014 at 16:47

JohnnyG said:
Instead of the DT90e why not go wireless with the DT92e - http://www.honeywelluk.com/products/Thermostats/Room-Thermostats/Wireless-Thermostats/DT92E/
That'll work perfectly with your 3 wire set up

Aah didn't see that one. Anyway, I got the DT90E from screwfix a bit earlier and installed it. Seems to be working ok, didn't blow any fuses so must have got the wiring right. Be interesting to see if it's a bit more accurate, at least you can easily see what the room temperature is with this one.