Why Does Red Light Go Off on Room Thermostats

[LizMac42]

Hi Experts - I live in a McCarthy and Stone Care Plus apartment. It has electrical underfloor heating with thermostats in each room. I was told to have all the main switches on and then control the room heats with the thermostats. At the present time I have set the thermostats to level where a red light comes on (there is no digital display) then I turned them to just above the 20 mark. However, after a while the red lights go off and the rooms cool down. So I am constantly having to turn them to get to the red light setting.
Are my thermostats faulty or am I doing something wrong.
Hope somebody can give me some tips or refer me to a good article on how to use thermostats properly

 

[Geoff1946]

It depends how much it is cooling by. Presumably it does come on again eventually?
There is always going to be a difference between the set temperature to switch off and the level at which it will come on again.
Also, ask your neighbours their experience and how they use the system.

 

[poni]

I would think the red light goes off because the floor has reached the set temperature,
you say about 20 what do you need to turn it to for the light to come back on?
also, the floor covering matters it must be suitable for under floor heating,

 

[ProDave]

Are these mechanical thermostats with a rotary dial that goes click as it reaches the turn on or turn off point?

If so these rely on a neutral connection to drive an internal "accelerator heater" to overcome the inherent hysteresis with a mechanical thermostat. Correctly wired they can be very good. But "forget" the neutral connection and they can have a hysteresis of several degrees, which is the behaviour you describe.

Any competent electrician should be able to establish if this is the problem.

If you feel competent take the covers off one and post a photo of what is inside, but turn the power off first as some thermostats have lousy unprotected terminals so will be a serious shock hazard with the cover off.

 

[michael8554]

When you get to the situation where the thermostat is set to 20C, but the red neon is off and the room feels cold.

Slowly turn the thermostat down until you hear it click.

Read the thermostat setting, let's say it clicked at 18C.

Now slowly turn the thermostat up until it clicks.

Does the red neon come on again ?

Did it click at about 20C ?

That sounds like the behaviour that ProDave explained, it sounds like you would prefer the clicks to be much closer together in temperture, by having the neutral connected.

 

[LizMac42]

Pro Dave and michael 8554 thank you for your replies - Yes, it IS that type of thermostat and it does exactly as you described Michael. Do I need to get new thermostats fitted (I have 5 of them) or can an electrician get the neutral connected (whatever that means)

 

[ProDave]

Do you feel brave enough to unscrew the cover from one and post a picture of the wiring connections?

If there is no neutral than an electronic (usually programable) thermostat would sort out your problem, but most of the electronic ones that work without a neutral need to run on batteries, which can be a PITA as some forget their programming when the batteries go flat.

 

[LizMac42]

ProDave - there doesn't appear to be a way of taking the front off easily - no screws visible anywhere - I will attempt to post a photo tho dont know if it will work

 

[LizMac42]

Hope you can see enough of thermostat

 

[ProDave]

Sometimes, if you pull the knob off (get a flat screwdriver behind it to ease it off) you will find a little screw that holds the front on that was hidden under the knob.

 

[Sharpend]

Does the outer shroud not just pull off?

 

[LizMac42]

No - have tried but no give at all - our apartment manager said another apartment owner had complained of same. She called an electrician who advised her to "have digital replacements that would show the warmth of the room rather than the floor" so maybe I will try the same route - thank you again for your time and interest