Pump (and boiler) on even though all zones off

[Deleted member 134500]

We have an oil-fired boiler and a three-zone programmer.

Some of the time it works fine, but not infrequently we get the following scenario.

20.30 last night: Programmer switches on the upstairs heating and the water heating. OK.
21.00 Programmer switches off the upstairs heating and the water heating.
OK, but the pump continues to run, even though all three programmer zones are now off and stay off.
The boiler is off most of the time but may come on in short bursts.
The boiler room is like a furnace.
No heat going to radiators (as expected).
A sound like flowing water is heard in the boiler room pipes. This sound quickly fades away if the boost is activated.
24.00 No change, zones still off, pump still running. We switch off the mains electricity.
07.00 Boiler and pump are now cool.
All programmer zones are still off. Mains electricity on. Boiler and pump start up immediately. Mains electricity off.
11.00 Mains on. Same behaviour. Mains off.
On past form, the problem should have cleared by around 17.00 and the mains can be left on again — till the next time.

We had the programmer replaced, but the problem persisted.
The electrician came back and rechecked all the wiring. Things went OK for a fortnight, then it recurred.

Ideas? Could it be the boiler thermostat?

 

[bill01803]

The switch in a motorised valve is sticking on, get an electrician that knows what he is doing to have a look

 

[Deleted member 134500]

Thanks, bill01803.

At the moment the system is behaving, but right through today it wasn't.

We kept the isolator off all day, just switching it on from time to time to see what would happen. Immediately it came on, the boiler and pump started up, even though all three programmer zones were off (i.e. "off all the time"). As far as I could see, all three motorised valves were shut — certainly the two sunvic ones were, the honeywell one is difficult to see but I think it too was off.

How did the system come right? We really needed some heat, so we switched the isolator on, and gave each zone a boost. After 20 minutes or so, we cancelled the boosts, and, much to our surprise the boiler AND the pump stopped, without having to cut the isolator.

Not a permanent solution, but better than nothing.