Thermostat powered by mains giving me problems...

[cruisewhu]

Hi there,

I cannot get my head around how my thermostat could ever work, but then I am not in the electrical/heating profession!

We have just moved into our new home. We have been here for 2 weeks and only now am getting round to sorting out our heating/hot water issue.

Our Drayton thermostat is powered by mains and only works when power is going to it. The power only goes to it when the switch for the heating/water is on.

Sounds straight forward.

So when the panel is on, and the heating is on, the thermostat kicks in and keeps the place at a cosy temperature.

Now comes the issue...

When the heating goes off, it then cuts off the power going to the thermostat. The thermostat then tells the heating that it's icy cold and kicks in on continuous. The only way to turn it off is by switching off the heating/hot water at the switch next to the programmer. i.e. no power to the programmer - everything is off.

The programmer is a Drayton Lifestyle LP522 Si Programmer Service Interval Model.
The thermostat is a Drayton RTSI Room Thermostat.

I'm hoping there is a really straight forward answer to this and that I'm just being a bit special!

Many thanks in advance!

 

[D_Hailsham]

There is obviously a wiring error.

Can you trace the wiring of the programmer and stat, then post the info?

 

[TCCHeating]

It sounds like the wiring from the programmer to the thermostat is ok. When the heating turns off you should lose the live to the stat so what you are describing is normal. i suspect you possibly have a sticking motorised valve. Whats the make and model of the boiler and what type of system do you have? Ie s plan or y plan?

 

[cruisewhu]

Thanks for your replies.

I can tell you the make of the boiler is Baxi although I cannot find the model as access is poor as you can see from the photos!

I cannot trace the wiring of the programmer I'm afraid.

I'm not sure how I would be able to see if it was an 's' plan or a 'y' plan?

 

[cruisewhu]

Front of Baxi boiler

• cruisewhu
• 26 Apr 2014
• 1

General set up

• cruisewhu
• 26 Apr 2014
• 1

General set up

• cruisewhu
• 26 Apr 2014
• 1

Programmer and power switch

• cruisewhu
• 26 Apr 2014
• 1

 

[oilhead]

If the thermostat switches off, as long as there is a feed from the programmer, the thermostat should still have a live feed. It is just the switched live you lose.
If I understand correctly, you are saying that when the programmer switches off, the heating switches to continuous without any thermostatic control. You need to follow the live feed back from the boiler when it is in this condition. I would suspect a faulty motorised valve, but you need to check your circuits.

 

[stardanny]

Possible incorrect wiring.

I can tell you the make of the boiler is Baxi although I cannot find the model as access is poor as you can see from the photos!

Your is a Baxi 100 HE

I can't see how will an engineer be able to remove boiler casing for servicing with that cylinder in the way....

Daniel.

 

[D_Hailsham]

I'm not sure how I would be able to see if it was an 's' plan or a 'y' plan?

By the motorized valves; there will be two.

I can see one of them. It's the silver box with a black lead at the bottom of the cylinder at the front. (The thing next door with a white lead is the electric immersion - just for emergencies.)

The second valve is hidden in the gloom on one side of the cylinder or the other. It will look like one of these:


View media item 11762 View media item 5946
If it's like the left pic (two pipes connected), you have an S plan; if like the right pic (3 pipes connected), you have a Y plan.

All the cables seem to connect to some sort of junction box near the bottom of the right hand wall. Is this correct? If so, can you post a pic of the box?

 

[cruisewhu]

Thanks for the information everyone.

I have managed to locate the second motorised valve and have attached photos of this one.

The first two are of the second valve (which I located on the right hand side of the cylinder).

The last photo is a close up of the one at the front of the cylinder.

Motorised valve on right of cylinder

• cruisewhu
• 27 Apr 2014
• 1

Motorised valve on right of cylinder

• cruisewhu
• 27 Apr 2014
• 1

Motorised valve on front of cylinder

• cruisewhu
• 27 Apr 2014
• 1

I'm guessing by the explanation that I have an 's' plan system?

 

[AndyPRK]

Someone painted the pipes a lovely silver!?

 

[cruisewhu]

Someone painted the pipes a lovely silver!?

Yes, it seems they did! There are a few odd things about the setup in our new place...

 

[TCCHeating]

The white valve is the valve you need to check as this is serving the central heating. It is a Drayton/lifestyle valve and they are not the best in terms of reliability. Remove the head with the black release tab on the side and check if you can turn the spindle easily with your fingers. If the spindle is free then i suspect a dodgy actuator head. If you have a multimeter it is easy to test these. If not call an engineer

 

[D_Hailsham]

I'm guessing by the explanation that I have an 's' plan system?

That's correct.

The central heating is controlled by the white valve at the side of the cylinder.

In your first post you said:

1. So when the panel is on, and the heating is on, the thermostat kicks in and keeps the place at a cosy temperature.

2. When the heating goes off, it then cuts off the power going to the thermostat. The thermostat then tells the heating that it's icy cold and kicks in on continuous. The only way to turn it off is by switching off the heating/hot water at the switch next to the programmer. i.e. no power to the programmer - everything is off.

The second sentence in no 2 may appear to be what is happening, but it won't be that. It is usually caused by the switch inside the CH valve sticking closed. The valve may also stick open, so the water can circulate round the rads.

The problem is that if this was happening the thermostat would not keep the place at a cosy temperature. It would get very hot.

As TCCH suggested, you need to remove the head and check if the spindle can turn easily by hand (it will be less than a 1/4 turn). If it sticks, apply a little silicon lubricant (NOT WD40). If not sticking, come back for more advice.

 

[cruisewhu]

Thank you all for your advice!

I shall attempt to remove the cover and test the spindle and I will report back tomorrow.

Many thanks again.