HELP PLEASE, anyone familiar with the workings of Underfloor Heating?

[ladybirder]

I control my underfloor heating by the thermostat on the wall of the area I want to heat. All my thermostats are set to 'Constant' as advised by the engineer but unless I want the CH on then the thermostat is set too low for it to kick in. I hate heat in bedrooms so I only ever have it on in the hallway/bathroom, kitchen/sitting room. Tonight I have the hallway/bathroom thermostat set so that the floor is lovely and warm in the H & B. I also have the sitting room/kitchen thermostat turned up even higher but the floors are freezing in the SR/K. Why?
Here is a clue to what might be wrong. The thermostats show a red light while they are heating up but when they reach the selected temperature they switch off. The one in the hall is still glowing red so has not reached required temperature. The one in the sitting room is flashing on and off (red then off) which shouldn't happen at all anytime. When the one in the hall switches itself off after reaching the set temperature, the one in the sitting room makes a loud clicking noise as it flicks on and off. Actually the noise comes from the cupboard where all the electrical and underfloor heating gubbins is. Sorry this is so long but trying to explain it properly.
Now my question is do I call out an electrician to the thermostat or do I call out an u/floor heating engineer as could it be that the thermostat is sort of calling for heating but something is stopping it getting it? In other words it isn't actually the thermostat that's at fault. I don't want to call an electrician who puts in a new thermostat and the heating still doesn't work. Get what I mean? Does anybody understand this please? Any help gratefully received. Thanks.

[buildersmate]

The whole tone of this sounds like you have electricity-driven UFH.
By far and away the largest method of of running UFH is via water-based systems that pump warm water (derived from a gas or oil-fired boiler) around pipes embedded in the substrate of the floor. The vast majority of UFH heating technicians will be involved in supporting that industry.
If you have an electrical system (which is a bit like glorified storage radiators but mounted in the floor), you need an electrician to test the connectivity of the elements and the control system.

[ladybirder]

Bless you BM I was hoping you would reply. My system is I believe pipes bedded under the substrate of the floor and powered by the Gas fired boiler as you say. This morning I checked the bedrooms thermostat and that also is flashing on and off and a clicking noise comes from the cupboard. So the only thermostat that is acting properly is the one for the Hall/Bathroom. This now leads me to think I should call out an UFH engineer rather than an electrician. Am I right BM?

[buildersmate]

OK - sounds like I got the wrong end of the stick and you have a water-based system.
The function of the thermostat in each of the 'zones' of the UFH is to sense the temperature in the room then send an electrical signal to the valve that controls the water flow through the appropriate zone. (There's a bit more to it in terms of functional logic circuitry but that is the gist).
The UFH gubbins are generally located in one single place (Where the pipes split out and return back are located) and if it is making a noise from there is sounds like at least one malfunctioning actuator valve.
A UFH technician will be well-used to dealing with this sort of defect so that is where I would go. The problem is that there are many manufacturers of UFH systems - a bit like there are many manufacturers of CH boilers. But because of all the extra gubbins associated with UFH, each supplier uses 'building blocks' (such as thermostats, actuator valves) that they do not manufacture themselves but they buy one from a components' manufacturer. For example, many thermostats are made by Danfoss, but they are just a component manaufacturer - they don't do UFH (as far as I know).
If you know who the manufacturer of your system is, I would ring a couple of UFH technicians from Yellow Pages and ask them whether they specialise in your system. I maintain my own UFH, I'm afraid - though it doesn't give me much trouble.

[ladybirder]

That makes perfect sense BM, thank you. A neighbour has just called and recommended somebody from check-a-trade.com who fixed their heating last year so I shall call them as they will know our system. Better do it now as I'm getting cold. Mind you the bathroom is warm so I shall have to sit on the loo with my lap top. What a picture.
Thanks again BM you have been so helpful.