Dodgy room thermostat

Auti

Hello, I have a thermostat to my gas central heating in my hall and it is over 30 yrs old. The past 2 days it has developed a fault (I think contacts are worn to turn on and off) in that it has the red light to say it is calling for heat but it has not turned boiler on. On fettling it I can get it to come on by firm tap on top of box and general wiggling, have also found it I press gently on the centre of the dial it turns off red light. I think it is coming to the end of its life.

Question: I have no idea where it is getting it’s power from to operate so I dare not touch it as no wish to be electrocuted. 

Is it easy to replace and to get hold of new one that is compatible with my boiler - Ideal Icos HE24 which was fitted 3/4/2006.

thank you for advice and I am still fettling with trv’s and saving up

victor2

Older ones like that are often mains powered and have the “heating contacts” as well, so 4 wires will go into the back of it, and the wiring is important because you’ve got mains voltage there!
newer ones tend to be battery powered, so only use two wires. Easy for a heating engineer to replace and simple thermostats are not expensive. You’ll need to isolate the mains feed to DIY.

FreeBear

victor2 said: newer ones tend to be battery powered, so only use two wires. Easy for a heating engineer to replace and simple thermostats are not expensive. You’ll need to isolate the mains feed to DIY.

The power to the boiler/thermostat will need to be isolated regardless of who does the work.

I'd suggest fitting a programmable thermostat to replace the old one along with the timer - Something like the Drayton Wiser if you have a system/heat only boiler, or Tado for a combi. Being able to set different temperatures throughout the day/week has the potential to save up to 15% in gas consumption. Although the research says 15%, the saving is likely to be around 5%, but if you use a lot of gas, it will quickly pay for itself.

grumbler

https://www.screwfix.com/p/honeywell-home-1-channel-wired-room-thermostat/26159

But you can replace it with a more modern programmable thermostat. And personally, I'd avoid anything battery-operated.

Auti

Thank you for your help. I will get a qualified person to do it as I do not have the skills needed re electricity part. If I went for different make would it matter as trv’s are Honeywell I think? 

Boiler has a tank in the loft and a hot water cylinder in the airing cupboard - not sure what system. 

There is a programmer (that I do not understand and does not do as I expect) under the boiler that predates the current boiler. I keep it on ‘boiler on all the time’ setting and control with the room thermostat in the hall. Hot water is kept off and when needed I press the 1hr boost button. Is this replaced too at the same time as room thermostat or are they a combined unit?

Guess I need to google heating engineer as the registered gas safe person I have used in the past (and trust) is booked up for ages! Any qualifications do I need to look out for given they will not be touching the actual boiler (I presume)? 

Thanks again 

grumbler

You don't need any special qualification for replacing a room thermostat. And it can be pretty much any basic room thermostat as it's job is only to open and close two contacts.

Albermarle

Boiler has a tank in the loft and a hot water cylinder in the airing cupboard - not sure what system. 

For info/future reference, you have what is called a traditional Vented system. 
A guide to vented vs. unvented cylinders | Viessmann UK

victor2

Worth learning how to better use your existing heating programmer. Significant savings to be had there if you're leaving it on heating 24/7. That is all the more reason to get a programmable thermostat, so you can effectively turn the heating off at night.

It is something any qualified electrician should be able to install. If you can get a mains powered one, then all the easier, as thew power feed is already there. If battery powered, I personally wouldn't be too worried. Typically two AA batteries needing changing once a year isn't too much of a headache.

Auti

@victor2 - this is the programmer - again over 30 yrs old as was with previous boiler. I have read instructions but as never really know when in or out or when for sure off I found it less good at giving me what I wanted than the room thermostat. I set room thermostat to 16c as I go to bed and 19c when I get up and if I am out all day set to 16c - then the boiler can do what I ask. There are reasons for not going below 16c in the house for humans. 

Thank you @Albermarle for naming my system and @grumbler and victor2 for saying qualified electrician can do the thermostat and programmer - will go for wired rather than battery.

Ganga

Yes be carefull with the electricity , we had a similar thermostat and i took the front off to decorate ,was standing next to it one day and as i was speaking to my wife put my hand on the wall touching the thermostat base ,got a hell of a shock ,we had left the electric on so the boiler could heat the water. 

victor2

@Auti, I've had a couple of those programmers and they were pretty good, allowing you to set separate timing schedules for hot water and heating, unless you had a gravity fed hot water system, which I did, so the hot water was on whenever the heating was. It can do regular daily patterns or 5/2 patterns to give you different weekend settings.

I'd leave that as it is (learning how to best use it), but go for the programmable thermostat. That timer will be the master, and the thermostat will only come into effect when the heating is on, like it does now.