Central heating won't turn off

[BigBadBarry]

Hi.

I know very little about central heating systems. My problem is the radiators are all stuck on full blast.

I am using a Honeywell thermostat, I think it's a DT90E.

The thermostat is set to 20. It shows room temp at the moment to be 26.5. There is no 'flame' symbol on the display, so the thermostat is apparently not asking for more heat.

The system also has a complex controller - a Horstmann ChannelPlus H37XL Series 2. I have selected the two channels called "Heating" and set both to "off". Still the rads are at full temperature, almost too hot to touch.

Does anyone know what the problem could be? And what can I do?

Thanks.

 

[TheHandyAndy]

I'm not a plumber, but you could try switching the hot water off too. Then if the radiators gradually cool, it might be that a motorised valve is stuck. these are easily replaceable.

 

[BigBadBarry]

I'm not a plumber, but you could try switching the hot water off too. Then if the radiators gradually cool, it might be that a motorised valve is stuck. these are easily replaceable.

Thanks. The water was off, but I've made sure it is by switching the controller to permanently off.

It's ridiculously complicated. We have solar panels, heating up the tap water, and if the water in the tank isn't hot enough, then the boiler will add some more heat.

The Central Heating runs through this Hortmann control unit, and a Logic Heat 12 boiler, and the Honeywell thermostat. I can't get my head around it at all.

So, the water is "off", meaning that if I run the hot tap, it will use the water in the tank at its current sitting temperature?

The central heating channels are off, so it shouldn't be adding any more heated water through the heating system?

I've taken the batteries out of the thermostat. What effect should this have, if the system were operating correctly?

Also, I seem to remember that the Honeywell should reset itself, if you hold in the up/down buttons together. Is that right? Mine does not respond in any way if I try that.

 

[BigBadBarry]

Streuth! The temperature is still going up. Just put batteries back in the thermostat and it's 27.5 in the room.

Is this dangerous?

How can I disable the whole system?

 

[TheHandyAndy]

The boiler shout have an on / off switch somewhere? If not, is it on it's own electrical circuit at the consumer unit?

 

[kbdiy]

Turn off the mains switch that supplies power to the boiler/controller. Usually a fused spur connection.

Sounds to me like the motorised valve for the heating is jammed open so constantly pushing heat round the rads.

 

[BigBadBarry]

Thanks. There's a switch marked "Heating" next to the Hortsman controller. I switched that off and the cupboard where is is went quiet. (There's a small red tank in there, loads of piping, a water tank which I presume is nothing to do with the central heating, and yet another controller with all sorts of digital display data - solar-panel related I gather).

Anyway I've switched the Heating switch off. Also there's an isolator switch next to the boiler in the kitchen, so I've switched that off too. We'll see if the rads start cooling down now.

I still have to get to the bottom of the initial problem - why isn't the thermostat switching the rads off when the room temperature is reached?

Sorry I'm such a dummy - I know nothing about these systems.

 

[BigBadBarry]

Turn off the mains switch that supplies power to the boiler/controller. Usually a fused spur connection.

Sounds to me like the motorised valve for the heating is jammed open so constantly pushing heat round the rads.

Many thanks. That sounds logical. Is there a way I can test this? Do you know where it sits? I am guessing next to the red tank near the heating controls?

EDIT: Got it! A Myson Power Extra - little white box. Silly question perhaps - should I knock it with a hammer to see if it frees up the moving parts? Or is there a test I can do?

 

[kbdiy]

Pictures would help. Controls, pipework, tanks etc. If you can post some then the experts here might be able to point you in the right direction but ultimately you will probably have to call a heating engineer if you don't have a good understanding yourself. No disrespect intended but conscious that time is of the essence where heating is concerned in winter .

 

[BigBadBarry]

Thanks very much - sorry for being so vague! I have taken some photos which might help...

Thermostat: Honeywell DT90E
Controller: Horstmann ChannelPlus H37XL Series 2
Valve: Myson Power Extra

We had not adjusted anything - the fault just occurred on its own.

Honeywell DT90E

• BigBadBarry
• 6 Feb 2014
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Hortsmann

• BigBadBarry
• 6 Feb 2014
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Valve

• BigBadBarry
• 6 Feb 2014
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General view

• BigBadBarry
• 6 Feb 2014
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Boiler

• BigBadBarry
• 6 Feb 2014
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[Whitespirit66]

It's probably the white motorised valve next to pump in 3rd photo. When you turn heating on and off, can you hear the valve moving/whining? Can you see the lever moving?

 

[BigBadBarry]

I don't hear anything from the valve when I switch it on or off, except water flowing/stopping flowing. I think I can hear sound coming from the pump.

Not sure where I would see the lever - there is a sort of grey slider button on the bottom (you can see it in the photo, through the loop of the white cable). When I went in just now, it slid freely from one end to the other. Now I've done a switch on/off a few times, it is held in position. Haven't seen it move by itself.

The thermostat is still giving a room temperature above the point it would want to turn on the heat - don't know if that matters?

 

[D_Hailsham]

There should be a second valve, like the Myson.

Can you post a pic showing all the pipework in the cupboard, ie. pic 4 but not close up.

 

[BigBadBarry]

Many thanks once again. I don't see a second one. I've photographed the whole of the system (see below).

The last two images show the tank and the solar panel system, which I don't think are relevant to the central heating system. There is a small box on the piping from the tank (centre of image 3), but no others I can see.

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• BigBadBarry
• 6 Feb 2014
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• 6 Feb 2014
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• 6 Feb 2014
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• BigBadBarry
• 6 Feb 2014
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• BigBadBarry
• 6 Feb 2014
• 1

UPDATE; Just found this, under the shelf in the same cupboard. Couldn't see it initially, but it's situated just under the wooden slats you can see in image 3 above. It says Honeywell on it - same brand as the thermostat in the living room.

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• BigBadBarry
• 6 Feb 2014
• 1

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• BigBadBarry
• 6 Feb 2014
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[mogget]

That silver box is the other motorised valve.