Boiler not switching off!
Discussion
It does sound like the microswitch on one of the valves is sticking. You mentioned that the levers on them offer resistance when you try and move them, this indicates the valves are closed, when they are open the levers will move with no resistance at all.
If the valves are closed and the boiler is still firing it can only be a faulty microswitch unless you have a wiring fault somewhere.
I'm a little confused as to why the house was a few degrees warmer though if the valves are closed when this happens, unless the CH valve isn't shutting fully and letting heat by.
If the valves are closed and the boiler is still firing it can only be a faulty microswitch unless you have a wiring fault somewhere.
I'm a little confused as to why the house was a few degrees warmer though if the valves are closed when this happens, unless the CH valve isn't shutting fully and letting heat by.
NiceCupOfTea said:
Can't answer that I'm afraid. I'm fairly technically/practically minded, but I find CH/HW very difficult to understand 
Your system sounds like it's fully pumped with a couple of 2 port zone valves so it's really pretty simple.As someone mentioned earlier, all the timer does is to drive the valves open, via the thermostat. Electrically, the CH & HW operate as two separate channels. If either of the zone valves is driven open then they trip an internal microswitch and that powers the boiler (and usually the pump is then powered by the boiler).
So assuming there's no bizzare wiring fault, the only possibility here is a sticking microswitch or a sticking valve. Most likely a sticking valve, hence the house is still getting hot.
If the BG man drains the system to replace the whole valve make sure he puts corrosion inhibitor back in. Might be worth getting some to have on hnad in case they don't do that. If you get it from B&Q etc you can always take it back if not needed.
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...
spike ST500 said:
if they do, they'll put in a BG branded one, which is made by Drayton... Insist they replace like for like instead...
Even though from your information it would appear to be the zone valve
You can insist all you want, they'll fit a BG branded part which will work just fine. Do you honestly think he's going to get a special permission from his manager to go to a merchants, pay double what they pay, just because you want a Honeywell. Not a chance.Even though from your information it would appear to be the zone valve
eastlmark said:
NiceCupOfTea said:
Update:
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)??
does sound exactly like the same problem I had in my post as above. A room stat will operate the valve only once it has a feed from the timer, so its not likely to be the problem. 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)??
In the internal wiring of a zone valve the opening and closing of the valve is electrically isolated from the switching.
The stat and timer will control the opening and closing of the valve. The physical movement of the valve then trips a microswitch which will control the boiler. That's why there are so many wires into the valve - it contains a switch and a motor.
On some valves the whole motor and switch can be replaced without needing to remove the physical valve - which requires draining down the system.
If you're confident to fault find then you could remove the valve cover and look at what is going on - is the microswitch not being tripped because the motor isnt moving through the full range or is something broken. You can get a new motor easily enough at screwfix or similar.
Careful because it will be 240V.
Otherwise just drain down and replace the whole valve. £50 or so for a valve and £10 for inhibitor.
Just for pedantic completeness, regarding the diagram of an 'S'-Plan system above...
The room stat will normally have a neutral, not always, but normally.
The pump will only be switched from the boiler on 'pump-overrun' gas boilers.
The bypass pipe requires an automatic valve.
28mm V4043H valves have a white wire which MUST be isolated.
You need some variety of expansion!!
There...that's put my head on the block!
The room stat will normally have a neutral, not always, but normally.
The pump will only be switched from the boiler on 'pump-overrun' gas boilers.
The bypass pipe requires an automatic valve.
28mm V4043H valves have a white wire which MUST be isolated.
You need some variety of expansion!!
There...that's put my head on the block!
Arthur Jackson said:
Just for pedantic completeness, regarding the diagram of an 'S'-Plan system above...
The room stat will normally have a neutral, not always, but normally.
The pump will only be switched from the boiler on 'pump-overrun' gas boilers.
The bypass pipe requires an automatic valve.
28mm V4043H valves have a white wire which MUST be isolated.
You need some variety of expansion!!
There...that's put my head on the block!
The OP has an programmable room stat, instead of a normal room stat, so will not have a neutral.The room stat will normally have a neutral, not always, but normally.
The pump will only be switched from the boiler on 'pump-overrun' gas boilers.
The bypass pipe requires an automatic valve.
28mm V4043H valves have a white wire which MUST be isolated.
You need some variety of expansion!!
There...that's put my head on the block!
The OP has a Potterton suprima, so is a pump over run boiler.
The other 3 points , although correct, are not important in the OPs question
sa v8 mate said:
You can insist all you want, they'll fit a BG branded part which will work just fine. Do you honestly think he's going to get a special permission from his manager to go to a merchants, pay double what they pay, just because you want a Honeywell. Not a chance.
If the engineer has to order a programmable stat from stores, then no harm in ordering an alternative make, if also stocked in the National Parts Center. It is unlikely he;d have a programmable stat on board.spike ST500 said:
The OP has an programmable room stat, instead of a normal room stat, so will not have a neutral.
The OP has a Potterton suprima, so is a pump over run boiler.
The other 3 points , although correct, are not important in the OPs question
Then perhaps the heading on the diagram should have been, "Honeywell S-Plan in regards to NiceCupOfTea's System"The OP has a Potterton suprima, so is a pump over run boiler.
The other 3 points , although correct, are not important in the OPs question
This forum has enough people on it who haven't a clue. People OFTEN search and read old threads for information. I at no time claimed that I was referring to the OP's system, merely ensuring that the diagram he'd posted was fully understood. I could have added that in many cases the flow and return connections might be plumbed the other way around and in many cases are DIRECTED that way by the manufacturer. I didn't want to confuse though...
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