This might seem silly question but am ignorant of such techy matters. I have a wall mounted Honeywell T40 Thermostat on the stairs wall and I want to know if it is still connected to central heating and can it be removed when next decorating. It has not been touched (adjusted) for well over 10 years, in fact the dial is cracked and doesnt work. I think it is the original which has been there for 42 years during which time the central heating boiler has been replaced twice (now Glowworm 30) and the hot water cylinder and cold water header tanks have been removed. Each room radiator has its own thermostatic valve which all work fine. So can I just remove it rather than have to replace it as it looks naff with the crack or is it still performing a function? tia.
Help re Honeywell T40 wall thermostat.
- Thread starter RRBDIY
- Start date
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Is your heating coming on, or have you disabled it/turned it off somehow for the summer?
Enable it and set that 'stat to maximum temperature (or until it clicks), does the boiler fire up and the pipes get warm?
If you turn the stat down, does the boiler shut down?
Are you sure you don't have another room stat somewhere, maybe a wireless one which has replaced your old one?
It would be unusual for a heating system not to have some sort of room thermostat and expensive to run without.
Enable it and set that 'stat to maximum temperature (or until it clicks), does the boiler fire up and the pipes get warm?
If you turn the stat down, does the boiler shut down?
Are you sure you don't have another room stat somewhere, maybe a wireless one which has replaced your old one?
It would be unusual for a heating system not to have some sort of room thermostat and expensive to run without.
Thanks for reply Harry. The heating is turned off for summer, ie. the 24hr central heating timer pegs on the boiler are all off but it works fine when they are set to switch on and off. I had assumed, probably wrongly that having the timer on the boiler negated the wall thermostat.
There is definitely no other wall thermostat apart from this on the stairs, and it is the only one we have ever had.
As I said each individual radiator now has its own thermostatic valve (TRV?). So each room and hallway are at comfortable tempuratures when the boiler timer is set and system working.
I gather from what you are saying every system should have a wall thermostat connected even if the boiler is a combi like ours. So I will assume ours is connected and therefore should be left alone and a bit of superglue to mend the cracked dial.
There is definitely no other wall thermostat apart from this on the stairs, and it is the only one we have ever had.
As I said each individual radiator now has its own thermostatic valve (TRV?). So each room and hallway are at comfortable tempuratures when the boiler timer is set and system working.
I gather from what you are saying every system should have a wall thermostat connected even if the boiler is a combi like ours. So I will assume ours is connected and therefore should be left alone and a bit of superglue to mend the cracked dial.
Why not just replace it with a new one, they are not expensive for the old fashioned, basic, wired room stat? Just three wires, probably and the jobs done.
Yes, certainly best to a room stat to save unnecessary wear and tear on your boiler and minimise your gas bills. The stat should be in a room or hall, where there is no TRV fitted on the rooms radiator.
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There should be live, neutral, switch wire and an earth?
The neutral is used to enable a tiny heater inside the stat, to make the mechanical stats more responsive to rising temperatures when the heating is triggered to on/ reduce the switching hysterisis.
It should have a neutral, if it has been wired correctly.
Like this - https://www.diynot.com/diy/threads/replacing-honeywell-t40-with-tado.495385/
Yes I know what you are saying. I saw a couple of pics and comments when trying to find an answer before I posted. Would take a photo but having issues with the phonecam. Definitely as I described. Nothing wired into #2 and earth is actually wired into the metal wall box not #earth as in your link. The wires all come from a single cable that looks exactly like lighting cable into a single ceiling rose. Old wiring convention of red - live, black - neutral, green - earth.
Just found this thread mentioning only 3 wires. If I understand it, it implies switch might be in combi boiler(?). I know our boiler does switch on and off when central heating is on.
Getting worried now if it is not wired correctly.
Just found this thread mentioning only 3 wires. If I understand it, it implies switch might be in combi boiler(?). I know our boiler does switch on and off when central heating is on.
Getting worried now if it is not wired correctly.
So worried in fact I forgot the link !!!!
https://www.diynot.com/diy/threads/wiring-advice.106754/#post-718550
https://www.diynot.com/diy/threads/wiring-advice.106754/#post-718550
Nothing to worry about, but as suggested in that thread, a T40 thermostat does need a neutral to the stat, to work optimally - who ever wired it up, maybe wasn't aware and thought it didn't matter.
I'm inclined to suggest, rather than buy a replacement for the T40 and trying to get a neutral to it, why not look at upgrading it to a wireless thermostat?
The actual thermostat is wireless, can be fitted where you like, even where the old T40 was. The remote base unit it communicates with, then connects directly into your wiring centre (probably where your airing cupboard is).
Its nothing at all to do with it being a combi boiler or any other type of boiler.
I'm inclined to suggest, rather than buy a replacement for the T40 and trying to get a neutral to it, why not look at upgrading it to a wireless thermostat?
The actual thermostat is wireless, can be fitted where you like, even where the old T40 was. The remote base unit it communicates with, then connects directly into your wiring centre (probably where your airing cupboard is).
Its nothing at all to do with it being a combi boiler or any other type of boiler.
If your existing thermostat is still connected to your new boiler (I doubt if it is) but if it is and you want a cheap easy replacement just get one of these .
https://www.toolstation.com/drayton...BlJCubkoJwpzq7kryTQRIlyMk7SJ9RfkaAqytEALw_wcB
https://www.toolstation.com/drayton...BlJCubkoJwpzq7kryTQRIlyMk7SJ9RfkaAqytEALw_wcB
That should be red - live, black - switched live, green - earth.
It will work without neutral connected, maybe not quite as responsive. A friend had a T40 and the neutral was not connected (incompetent installation) and he didn't notice. It failed because it's a filled system and the fluid must have leaked. In a previous house I had a Honeywell T403A, which uses a coiled bimetallic strip. Didn't have an anticipator but worked fine. Probably still does, I must ask the ex sometime!
Thanks for reply. My comment was just regarding old wiring colours but I did notice today, whilst wallpapering around it, that there is a tiny piece of red insulating tape on the black wire so I think that probably means switched live.
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