Central heating seems to be firing up for a short time, when not called for?

[ericmark]

I will guess a micro switch in the motorised valve had stuck, but having a problem working out which motorised valve, it is C plan, but supplies a flat and main house, each with its own motorised valve, the fault has cleared now, the boiler seemed to fire for around 5 minutes, which I assume is the time it takes DHW to warm up, and turn boiler off.

I am trying to think of a way to test next time it happens, to see which motorised valve micro switch has stuck, but can't think of a method to test.

 

[RandomGrinch]

Does your oil boiler have an independent frost stat?
It has been chilly the last couple of nights?

 

[ericmark]

Does your oil boiler have an independent frost stat?
It has been chilly the last couple of nights?

Good point, but it is in the flat under main house, which since half buried in the hill side, never gets really hot or cold, so would not think that is the cause, i did a plan for the wiring when I added the motorised valves.

The problem before I added the valves was running one pump would circulate the water in reverse in the other circuit, I noted the problem when I doubled up on the thermostat for house, 1, 2, 3, 4, 5 now also go to a wiser thermostat, as hall cooling too slow, tested at 5 and it did disconnect, I did not test at 7 on upper wiring centre, but since red demand neon on at the boiler, I would think line.

I do not activate boiler for DHW any more, it clearly heats it when central heating is running, they is no way to turn it off, but seems unlikely the Nest Gen 3 is the cause, seems far more likely the V3 micro switches in the motorised valves, but the access is not good to get at the valves, and likely will need to employ some one to change them for me. I am getting older, and have to accept it. But when installed the heating guy admitted he did not understand the electrics, and to be frank I do not understand the plumbing.

In my mind, if should have not needed the motorised valves, if all TRV's are closed, there should be no radiators warm, but may be as a three story house, the radiators did warm up.