Help! Heating on only when hot water on!

Floxxie

I'm having a nervous breakdown over my central heating system which is 3 years old. The set up is there is a Potterton boiler in the kitchen and the tank is in the airing cupboard on the third floor.
The heating is on a constant on, the thermostat situated in the hall is set to 19 degrees. The hot water is set on the timer to come on in the morning and the afternoon.

The system's latest trick is to provide a small amount of heat when the hot water is timed to come on. The radiators do not reach the temperature as controlled by the hall thermostat and when the water reaches the required temperature then the boiler and subsequently the heating turns off.

Any suggestions as to what the problem is? It has already cost us £350; £50 for a plumber to change the valve in the tank around (apparently put on upside down) and £300 for the boiler service engineer to change the programmer box and change the valve back again. This was done yesterday and the heating worked extermely well until this morning when I thought I would turn it down to 15 degrees whilst I was out. I came back to find a cold house and have been clock watching waiting for the hot water to come on (it doesn't come on if I switch it to hot water constantly).

Any help or guidance before I get ripped off for even more money, would be appreciated! Thanks.

Threewheeler

Sounds like you've got a sticky thermostat, try turning it right down and gently tapping, then right up and tapping again. If sticky it just might work once or twice, you will then need a new thermostat. There are two different thermostats, one on the boiler as water temp control and seperate one usually in hallway.

Floxxie

Hi Threewheeler,

Thanks for the suggestion; I have some questions about it (if you don't mind):

1)The thermostat still clicks but the boiler doesn't kick in - could that be the 'sticky' part of the thermomstat i.e. we need a new hall thermostat
2) Why would the hot water then 'control' the turning on of the heating (albeit not very successfully)? Could that be something to do with the valve in the airing cupboard.

I'm going to try it out now....

Threewheeler

Yes.
1. If the thermostat clicks, it still may not be making a good contact, I had to replace mine after a while as the contacts got burnt.
2. Normally ther is a motorised valve in the airing cupboard that opens and closes to add the heating to the rads when switched by the thermostat.
You could check if you have one, then with everything switched on check whether the valve lever moves back and forth , i.e. when thermostat on max valve opens (note the lever is likely to be able to be opened manually into a slot at maximum position, to hold the valve open ). This could be tried, if the boiler starts be patient as takes a little while to activate and the boiler could have a sequence timer to go through all the process to restart.
By the way I presume that you have checked that the boiler has not gone to lockout, a light shoud show you if it has?

Floxxie

Hi Threewheeler,

Tried the tapping, no joy.

Will have a go at the valve side of things and report back...

No the boiler has not gone to lockout; it's showing no external call for heat - mmm, I suppose if the thermostat hasn't got proper contact then it wouldn't be communicating with the boiler. Shouldn't the plumber and the service engineer picked up on this?

Thanks for your advice, I'm off to have a lookin in the airing cupboard.

Floxxie

Hello Threewheeler,

Didn't make it upstairs as husband had already found the manual override lever, moved it and voila heat! He put it back and I turned down the thermostat in the hall, a red light went off and when I turned it up the red light came on; this sounds as if it is doing what it is supposed to be so do you think that there is a dodgy connection in the hall thermostat?

If so, woudl there be a problem using the manual override until a new thermostat is fixed and would I need an electrician to carry the work out?

Thankyou very much!

Threewheeler

Sorry, out for a while,I don't think that it would matter, I have used manual override for a while before changing the power unit to the heating switch valve, which is the electric part of the mechanical valve. Sounds more complicated than it is. Just to confirm when you turned the valve manually the boiler started up O K and you got heating to rads? yes did the valve open itself after fiddling with it, sometimes it can get stiff and just by manually opening and shutting it you can effectively cure your problem. Advise me of your results.

pollsdolls

Hi, i have shown this post to my husband Roger, who is a Corgi Registered heating engineer. Here is his reply. Hope it helps.................

Hi my wife has just asked me about the problem that you are having with your heating system, don't be to hasty about thinking that it is a t/stat problem it is probably a problem with the motorised valve.

With you pushing the lever to the manual position you have done what the synchron motor should be doing. To check it out, set the clock to have the heating and hot water on constant.

Turn the hall stat and cylinder stat up, gently push the lever on the motorised valve to the manual position. If you can feel a resistance about half way through the travel of the lever, the synchron has not opened the valve.

The correct way to check this out is to, make sure that there is power to the synchron, which would prove that the stats are working. Therefore leading you towards there being a fault on the motorised valve.

Some synchrons can be changed, otherwise you will have to change the whole motorised valve. Good luck and the bill will be in the post!!!!!!!

NB ******. This will only work if all components are wired in correctly.

Floxxie

Ok, thankyou to you both; I noticed the rapid introduction of technical terms - have printed off both responses to see if I can get my head around them!

Pollsdolls, your husband's repsonse about things being wired correctly rings alarm bells. The original contracting firm who put this system in were sacked by the builders for their incompetence....we had to have our hall thermostat wired correctly.

Now the other part about his post was about having the heating and hot water on at the same time to test and I think that is where our problems have been clouded over. Up until now we have had the water and heating on constantly. This is because we didn't understand simple things like timers and not having to heat the water up 24 hours a day. Thinking back it was around the time that the hot water was put on timer that the heating only came on when it did, so I thought it might have something to do with the valve (and that might be the wrong word) in the airing cupboard.

Threewheeler, yes as soon as manual override was in place, the boiler kicked in and the rads heated up. Switched back but the hot water and heating were both on so would expect the rads to stay on for a while...Right just turned off water and tried heating alone...boiler does not kick in.

Does the boiler receive instructions from the hall thermostat via the airing cupboard valve (which I am assuming is set by the programme controller by the boiler?). Does the synchron control the valve for both water and heating or heating alone?

Finally who would get to the bottom of this problem? I have had a plumber and a service engineer out. Do I need to get an electrician out to test the valve and check the contact points for the hall thermostat?

Many thanks for your support; I just want heating that works!

robby-01

the problem is likely to be in the wiring,the diagnostic test by the corgi guy is bang on and he knows his stuff.A lot of systems like this get wired wrong at the start and never work as they should.
It can be hard getting someone to put it right as a lot of sparks dont understand the mechanics of the system and end up making a mess of it ,and a lot of plumbers wont touch electrics.Try a reputable local heating firm who may employ their own sparks, someone with the right experience should sort that in an hour or so.

Canucklehead

Good morning

Corgi guy in the canucklehead chair...

I might have missed it but looking back through the thread I don't see any mention of whether it is a three port valve or two, two port valves. The difference is that the three port valve will always give hot water . If the motor fails it will not move over to c/h. Manually opening it will give heating ,but only as long as there is demand for hot water.Usually opening a valve manually does not make the electrical contact .
Roger's advice is correct (and robbie).... you do need someone to follow through the wiring ,a good heating guy or a heating savvy sparks.

Good luck.