Boiler not switching off!
Discussion
Could use some help please!
We have a Potterton Suprima 80 boiler with separate heating and hot water circuits. Timer controls HW as normal, with the heating side of the timer set to "ON" - timing of heating is controlled by a remote digital thermostat/timer. (Honeywell CM927) Hope that makes sense.
The timer/stat were installed a couple of years ago and have worked very well.
All was fine until a couple of weeks ago. We have a British Gas "servicing" contract (ie, bloke comes out, hoovers it, and checks CO levels every year!) - he did his stuff and left.
It was fine.
Went away over Christmas and put it into its holiday mode, where it maintains a minimum temperature that you specify (16 C in this case).
Came back to find the house baking - 34 C according to the thermostat, with the "target temp" still 16 degrees but the boiler full on. Had to override the thermostat base station (bit actually attached to the wall) by toggling it on and off.
Just today noticed it was very hot again. Target temp 20C, actual room temp 23C. Stat saying boiler was off, Stat base station light off indicating no call for heat. Boiler on full whack. Toggled base station call for heat button on and off, and boiler switched off.
I had initially suspected the thermostat batteries, but the low battery indicator was not on. Now I don't think that is the problem at all, as the base station was suggesting there was no call for heat, but the boiler was on.
Is there some way the gas engineer could have buggered up the boiler so that it is not always detecting a CFH signal correctly? I thought it was a constant voltage / no voltage for heat / no heat, rather than a "toggle" signal that it might miss...
Does this make sense to anybody?
We have a Potterton Suprima 80 boiler with separate heating and hot water circuits. Timer controls HW as normal, with the heating side of the timer set to "ON" - timing of heating is controlled by a remote digital thermostat/timer. (Honeywell CM927) Hope that makes sense.
The timer/stat were installed a couple of years ago and have worked very well.
All was fine until a couple of weeks ago. We have a British Gas "servicing" contract (ie, bloke comes out, hoovers it, and checks CO levels every year!) - he did his stuff and left.
It was fine.
Went away over Christmas and put it into its holiday mode, where it maintains a minimum temperature that you specify (16 C in this case).
Came back to find the house baking - 34 C according to the thermostat, with the "target temp" still 16 degrees but the boiler full on. Had to override the thermostat base station (bit actually attached to the wall) by toggling it on and off.
Just today noticed it was very hot again. Target temp 20C, actual room temp 23C. Stat saying boiler was off, Stat base station light off indicating no call for heat. Boiler on full whack. Toggled base station call for heat button on and off, and boiler switched off.
I had initially suspected the thermostat batteries, but the low battery indicator was not on. Now I don't think that is the problem at all, as the base station was suggesting there was no call for heat, but the boiler was on.
Is there some way the gas engineer could have buggered up the boiler so that it is not always detecting a CFH signal correctly? I thought it was a constant voltage / no voltage for heat / no heat, rather than a "toggle" signal that it might miss...
Does this make sense to anybody?
A bit of googling has suggested people have had similar issues when their zone valve has a dodgy microswitch. Could this explain why the stat isn't calling for heat but the boiler is on? We have separate valves for HW and CH.
We have BG Homecare 200 ( http://www.britishgas-savings.co.uk/british-gas-se... ) which doesn't specifically mention valves but does say "Repairs to central heating boiler, controls, radiators, pipework and hot water system" which I would hope covers it (nothing on the higher levels says anything about valves)
We have BG Homecare 200 ( http://www.britishgas-savings.co.uk/british-gas-se... ) which doesn't specifically mention valves but does say "Repairs to central heating boiler, controls, radiators, pipework and hot water system" which I would hope covers it (nothing on the higher levels says anything about valves)
Rickyy said:
My first thought was a sticky microswitch, but this wouldn't allow the radiators to get hot as the valve would be closed.
Although it could be possible that the whole valve is getting stuck in the open position. What make/model is the CH zone valve?
They're both silver Honeywell valves - no obvious model numbers, one says V4043H1106 and the other V4043H1056 but they may be serial numbers. They both have metal switches on the back with 2 positions - manual & auto. One of the switches seems to be in the middle, while the other is set to auto. No idea what that means.Although it could be possible that the whole valve is getting stuck in the open position. What make/model is the CH zone valve?
Re: using the contract - yes, I fully intend to, but I would like to have an idea of what is wrong first.
Update:
Heating did the same thing again this evening. Went up and checked the zone valves - one appears to go into the bottom of the hot water tank, the other goes down through the floor - I assume the latter is the CH zone valve. Both of the little metal switches were in the same place, both seemed to move with a little pressure. Manually toggled the thermostat on/off but the boiler didn't shut down. Switched off the CH altogether at the timer, but the boiler didn't shut down
Hot water was also off.
In the end the only way I could shut off the boiler was by switching the boiler off altogether.
I'm not terribly confident about waving multimeters around live distribution panels so will leave that for now.
Am I right in thinking that if switching off the CH & HW at the timer doesn't stop the boiler, it can't be anything to do with the 'stat (as the stat is effectively a switch inline with the timer)??
Heating did the same thing again this evening. Went up and checked the zone valves - one appears to go into the bottom of the hot water tank, the other goes down through the floor - I assume the latter is the CH zone valve. Both of the little metal switches were in the same place, both seemed to move with a little pressure. Manually toggled the thermostat on/off but the boiler didn't shut down. Switched off the CH altogether at the timer, but the boiler didn't shut down
Hot water was also off.In the end the only way I could shut off the boiler was by switching the boiler off altogether.
I'm not terribly confident about waving multimeters around live distribution panels so will leave that for now.
Am I right in thinking that if switching off the CH & HW at the timer doesn't stop the boiler, it can't be anything to do with the 'stat (as the stat is effectively a switch inline with the timer)??
spike ST500 said:
lets just hope it does the problem while the guy is there!
I'd be looking at the CH valve sticking on myself.
Indeed. It seems to behave itself in the morning, just late afternoon & evening it just stays on. I had the boiler off for most of the evening and tried to switch it on before I went to bed so we would have hot water this morning, but it just fired up despite the stat being low and the hot water timer off...I'd be looking at the CH valve sticking on myself.
Did the batteries yesterday morning just to be on the safe side but it did it again last night. Hopefully the BG engineer will be able to track it down even if it's working ok on Tuesday. A bit worried that he may decide to rip out the (expensive) stat and timer that I fitted with my dad 18 months ago, and replace with cheap crap...
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