Help with central heating in new house.

[littlepigeon]

Hi all,

I'm hoping someone can help with my central heating in the house I've just bought.

Its an old Edwardian property with what i have worked out is an open vented system with header, expansion and hot-water tanks all up in the loft.

I have a central heating only boiler in a boiler cupboard outside which feeds the central heating and the element in the hot-water cylinder.

The main problem i have is that when the hot-water cylinder stat is up to temperature the central heating goes off.

If i go in the loft i and play with the stat on the cylinder i can see the valve motor turning but what also happens is the stat seems to shut down the boiler.

Can anyone think as to why this would happen and just confirm that this is definitely incorrect.

Many thanks
Gav

 

[stem]

Are you referring to a 3 port motorised valve?

If so, in the central heating only required position (ie when the hot water goes off but central heating is still required) the valve motor winds the valve fully across to the central heating only position and should operate a microswitch that makes the orange wire from the motorised valve 'live' This orange wire is what runs the boiler, and it sounds as if this is not happening.

If you are able to use a multimeter safely then disconnect the orange wire from where it connected to the heating system wiring and switch on the heating only, making sure the room thermostat is 'on' and see if the orange wire becomes live. If it doesn't, a new valve (or valve head) is required.

Just to complete the picture, when hot water only, or hot water and central heating combined are required, the boiler is controlled by the cylinder thermostat as you describe. The orange wire takes over control only when central heating alone is required.

 

[D_Hailsham]

Do you have just one valve and does it look like this?

View media item 11762
If so, how many water pipes connect to your boiler? If more than two, you probably have a pumped heating, gravity hot water system. The motorized valve and cylinder thermostat turn it into a C plan.

View media item 827 View media item 73
The problem is probably caused by a faulty micro-switch in the valve.

 

[littlepigeon]

Hi

Not sure if its a 3 port or just a 2 port but i appear to have two of them that are linked to what looks like a master control box (honeywell) that all the electrical wiring goes into.

One is blue and i think is an old british gas one (bgmvsp-2) and this appears to work off the cylinder stat. There is another one but this doesn't appear to move, unless its uber quiet. I'm thinking maybe this should work from my room stat maybe, but that has no effect on anything, on or off it doesn't make any difference to the central heating or the hot water?

My clock in my kitchen also only has constant - on - off settings and nothing to just allow for water only which i found quite weird.

 

[D_Hailsham]

i appear to have two of them that are linked to what looks like a master control box (honeywell) that all the electrical wiring goes into.

Do both valves look similar to this (it's a two port)?

View media item 11762
If so, you have an S Plan system. One valve controls the hot water, the other the heating.

View media item 71 View media item 72

One is blue and i think is an old british gas one (bgmvsp-2) and this appears to work off the cylinder stat. There is another one but this doesn't appear to move, unless its uber quiet. I'm thinking maybe this should work from my room stat maybe, but that has no effect on anything, on or off it doesn't make any difference to the central heating or the hot water?

You are correct; that's how they should work.

My clock in my kitchen also only has constant - on - off settings and nothing to just allow for water only which i found quite weird.

Sounds as if the system has been updated from C-Plan to S plan without changing the programmer. You need a new programmer. This will then enable you to have independent control over HW and CH.

 

[littlepigeon]

Basically there was a flood and a lot of pipes burts just as we were buying it, before we bought it it had a digital programmer in there but now its been replaced with an analogue thing with a red and blue wheel in the top corner that is spun by a moving clock.

I think this is the wrong type of clock for the system but also that the stat that was replaced at the same time as the clock is wired in wrong so is having no effect on anything,

Sounds like this honeywell box where all the electrical wiring is going has been connected up wrong.

I'm not at home at the min so cant look at the valves again. I know they both look different but will get a picture in a bit if poss.

Thanks very much for your help so far.

Cheers
Gav

 

[littlepigeon]

Ok , got some piccys that may help.

This is the system from a wide angle

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• littlepigeon
• 18 Mar 2010
• 1

This is the valve that does work when the cylinder stat switches on or off

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• littlepigeon
• 18 Mar 2010
• 1

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• littlepigeon
• 18 Mar 2010
• 1

This is the other one i can see but doesn't seem to do anything

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• littlepigeon
• 18 Mar 2010
• 1

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• littlepigeon
• 18 Mar 2010
• 1

This is the box they are all connected to

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• littlepigeon
• 18 Mar 2010
• 1

 

[ChrisR]

It could be all sorts of things, but very likely the grey topped valve is not working, and has been latched in the MAN (open) position, so you get CH heat when the hw is heating.
Very likely it isn't wired properly as well, if the same guy who did it as got the timer configuration wrong.

Get the dud valve working, which may mean a new motor or a new head or a new valve. Unless it's just not connected!
Then Start over. Identify all the wires which go into the connection box - write it down.
Then connect as per the standard layout, and it'll work.
Sounds simple, but first time you go in there, there's a lot you can get wrong.
Alternative is to call a heating engr, who will get you sorted in an hour, unless either
1) there are wires missing
2) he needs to change the whole valve
3) you have multiple faults.

 

[littlepigeon]

Is there anyway of manually switching that valve that isn't doing anything to see if that actually gives me central heating when the waters up to temp?

I'm waiting for a call off one of the guys that fitted the boiler but last time he came out he tried to tell me what was up in the lofty was nothing to do with him and didn't seem very interested in looking at it for me Bloody blame culture hey!! just do the bloody work