Alpha 240P CH problems

[tomosman]

We have an Alpha 240P as we have a problem with the Central Heating turning on at random. Could anyone please help us?

History:- A few months back, we were having problems with intermittent hot water. Our plumber replaced the diaphragms and springs in the diverter valve and since then the hot water has been fine.

However, since then, the central heating has been turning on intermittently when not required. The burner can fire up from anywhere between a short blip and several minutes. We have taken to turning the boiler off at the mains when not needing HW to prevent the CH from turning on.

The Alpha help desk suggested it could be the micro-switches on the diverter valve or the external controlled. We have isolated both and they are not causing the issue.

Both Alpha and our plumber then suggested it could be the main circuit board. This has been replaced by a reconditioned board as new ones are over £200. The problem is still occuring though.

When the CH randomly fires up, the rear piston in the diverter valve is extended, triggering the micro-switch, however, the heating does not always fire when the piston is in this position. If the piston is down, the heating does not fire up.

This occurs with the rotary switch in both the CH & HW and the HW only positions but not in the centre position.

We've searched through the forums and we cannot find anything similar. Does anyone have any ideas what this could be?

Thank you for your help,

Tom

 

[Boilerman2]

No I don't know what the fault is at the moment HOWEVER we have a 240X which is doing exactly the same as yours, so far we have replaced the microswitches, the external control interface, disconnected the room stat, we have not gone as far as replacing the main PCB yet as we can find no evidence to support doing this, but every couple of days the boiler will be at rest when suddenly it starts up in heating mode for no reason

if and when I find the answer I will let you know
FRUSTRATING!!!!