Swapping thermostats

Hello,

Looking for some advice, I recently had to call upon a well know heating and plumbing insurance company to replace a faulty digital thermostat. They replaced it whilst I was on holiday with an analogue one. Which I was not pleased about for obvious reasons. I needed to establish a price to get this changed back to a digital one as they refused to come back to fit one. When I looked behind the fascia to see what wiring was there to support that I found 3 wires. 2 in the therm and one exposed and unlabelled. At this point I am really disappointed and thinking its not safe and whether or not they have done there due diligence or whether a digital and programmable (which I had before) can be fitted now. Does anyone have an opinion or knowledge on this? Thanks very much. Ross

I will not try be to rude ross. I think you might be biting of more the you can chew .
do you self a favour get a spark in.

Thanks for a very quick response!

Agreed, I have no intention of messing with this lot as I don’t have the know how. The idea of checking behind was to see what kind of thermostat I would need (research only). The thing for me was I wanted to get a bit of a clue from someone who did know, is this potentially dangerous I.e. urgent that I need to get said insurer back out sharpish. Thanks.

The bare conductor is the CPC and should be sleeved green and yellow and terminated in the far left terminal. The thermostat should ideally have a neutral which you don't have. The reason you should have a neutral connection with a mechanical thermostat such as the one that has been installed is to reduce the hysteresis of the bi-metal strip. With a line and neutral connection, the inbuilt resistor will heat the bi-metal strip in the thermostat so you don't get a big swing in temperature. Without this you will likely get a swing in temperature of around 3 degree above and below the desired set point before the heating turns off/on. With a digital thermostat, which you say you had before, you wouldn't usually suffer much hysterises as they are normally accurate to 1/4 to 1/2 a degree.