Boiler firing up when heating & HW off?!

[BritishBeef]

I have had fun and games with our CH over the last few years. It has had a few issues that have required several visits from heating engineers to fix.

A new issue has now just arisen.

I have recently noticed the boiler firing up even when the central heating & hot water is switched off.

When this happens, the radiators on our 2nd floor get hot but the other lower 2 floor rads stay cold?!

If I turn the heating on and call for the CH from the thermostat then all the rads get hot as they should.

The HW is functioning fine too. It's only when it's all switched to off or the thermostat is turned right down so it's not calling for heat that the boiler sometimes still fires up and the rads on 2nd floor get hot.

This doesn't happen all the time. Right now everything is on auto and heating & hot water should be off - and it all is. The boiler is off.

I seem to mainly notice this issue at night when I go to bed. I hear the boiler is on so check and the issue is happening. Also when the issue is happening the hot water pump is on. I left it running last night but switched the boiler off at isolation switch and by the morning everything had switched off as it should be (boiler and pump).

Anything this newbie can check before calling someone out again?

For your info my system is:

Boiler: Ideal Classic FF350
Thermostat & programmer : Danfoss FP715
Honeywell motorized valve (replaced a couple of years ago)
Pump: Grundfos Superselectric UPS 15-60

Any help greatly appreciated.

 

[picasso]

Is there a frost stat fitted ?

 

[Agile]

I doubt that diagnosing the fault is likely to be possible as a DIY.

Most often a faulty motor valve or programmer but needs inspection and electronic tests to identify.

Tony

 

[BritishBeef]

No idea about frost valves, sorry picasso.

Ah ok Agile, I feared as much. Will get someone out then.