Thermostat issue

[reb78]

I have an old room thermostat and even though I can hear it clicking It is not switching the boiler on for the central heating. The boiler is working as its coming on as it should for hot water and reactimg correctly to the stat on the hot water tank.

Two questions.
1. Can i 'test' the stat by bridging the two wires (black and red) below? Presumably thats what the stat does to send a signal to the boiler?
2. Is this a two wire stat? I am assuming earth isnt included in the number of wires?

 

[Kayos]

Yes you can bridge. A 3 wire takes a neutral to that resistor in the diagram, it is called an anticipator and helps the stat react quicker

 

[waddycall]

What other controls do you have e.g. two channel programmer motorised valves etc?

 

[brightspark]

the thermostat doesnt send the signal to the boiler it either operates the pump on a gravity hot water and pumped central heating or your systems a y or an s plan or is your boiler a combi ??

 

[Endeleus]

As above, check the thermostat, timer and motorised valve. All three can go faulty to cause the same issue.

Mechanical thermostat is probably the least likely to fail out of the three, motorised valve is the most likely (assuming an S plan system, orange wire triggers the boiler.

 

[reb78]

Bugger. Not simple then.

So I have had to travel for work (another story and against my judgement). The place has been empty since before Christmas as my lodger cant return for the moment. I got in at 5, it was freezing so I put the hot water and heating on. All seemed fine but after a while I noticed the rads were off when they should have been on. The boiler fired for hot water and the rads started to warm up again. Turn the water off and the boiler went off even though the stat should have been calling for the heating to be on. Sounds like it's more likely something else?

I have BG homecare here so may have to call them out as I dont have masses of time currently!

 

[reb78]

What other controls do you have e.g. two channel programmer motorised valves etc?

Two channel (HW ans CH) programmer ans one valve

 

[reb78]

the thermostat doesnt send the signal to the boiler it either operates the pump on a gravity hot water and pumped central heating or your systems a y or an s plan or is your boiler a combi ??

Ah. Ok. I think the details are in my last reply. It's not a combi

 

[reb78]

Ok, so bridged the stat and, as I think you predicted....., nothing happened, so I guess the fault is elsewhere

 

[brightspark]

have you got a 3 port valve on top of the pump. if you have theres a slider lever on it slide it to the right and heating should come on . if not the motorised valve motor has probs had it

 

[Mikes]

It's not quite clear what you've got but if a single control valve with 3 ports then it sounds like this is faulty as when you want heating without hot water or the hot water is satisfied, then the contact on the motor should change over to allow this. Your test described above is the normal test to prove this.

 

[reb78]

have you got a 3 port valve on top of the pump. if you have theres a slider lever on them it should be open pulled to the right if heating is on . there spring loaded if it isnt pull it across and see if heating comes on . if it does the motorised valve motor has probs had it

I think its after the pump on the pipe but I will check and move the lever as you say

 

[reb78]

It's not quite clear what you've got but if a single control valve with 3 ports then it sounds like this is faulty as when you want heating without hot water or the hot water is satisfied, then the contact on the motor should change over to allow this. Your test described above is the normal test to prove this.

I'm pretty sure it's a simple 3 port valve. I will check

 

[reb78]

This is the pump and valve. Looks to be a lever on the right (which you cant see in the photo!) but it wont move easily and its crappy plastic so dont want to force it.

 

[brightspark]

the levers spring loaded. if the powers off pull it over to the right and it will slowly move over. theres a bit of pressure on them and takes a few seconds to move . if its powered up it will move over on its own if its working

 

[Martinb]

Remove the valve head (blue Part) and underneath is the part that moves turn it manually to heating ( the pipe not going to the tank)

 

[brightspark]

Remove the valve head (blue Part) and underneath is the part that moves turn it manually to heating ( the pipe not going to the tank)

that wont bring the boiler on if the motorised head motor is faulty it will only show if the valve is siezed which is very rare

 

[Martinb]

Turn on hot water on clock and it will

 

[brightspark]

Turn on hot water on clock and it will

yes but it wont show if the head motor is working

 

[Martinb]

It will get his heating on till BG show up Though