Boiler comes on outside the times set on the timer

[OasisFan79]

On two occasions now (Monday this week AM and PM and again today) we noticed that our boiler was on when it shouldn't have been.

Wondered if anyone could shed any light on what might be causing the problem?

I noted down everything that I could:

1. The boiler fires up outside the times set on the timer.

2. When this occurs, the boiler fires up, displays C (meaning that heating or DHW is being supplied) and the burner light stays on.

Then the boiler quietens down (stops pumping or burning) and the C remains on but the burner light starts flashing again.

Then the process repeats.

If I turn off the power to the timer and the boiler (same wall switch) and turn it back on, the process then seems to repeat i.e. as soon as you turn the switch back on, the boiler fires up, C light is on and burner light flashes.

Turning the boiler off but leaving the timer on doesn't seem to make any difference. In fact the boiler fires up and on immediately after turning it back on.

Setting the timer to off on both heating and water and then power cycling the boiler seems to resolve the issue. We can then put the timer back to the timed position for water and heating.

It's happened twice so far: Monday this week and then again today (so 4 days in between).

In terms of hardware, we've got the following:

Ideal ICOS HE-15 Boiler
Drayton LP522 timer
Drayton thermostat


Thanks in advance

 

[45yearsagasman]

View media item 44939View media item 38425Got anything like these in the airing cupboard?

 

[OasisFan79]

There are a couple of similar devices in the airing cupboard:

View media item 96210
View media item 96209

 

[45yearsagasman]

It could possibly be one of those valves causing your problem, and most likely the white valve. They have a reputation of sticking and the micro switch staying closed keeping the boiler switched on. A good repair man would find that fault in no time. If you intend to DIY then a multimeter would be useful.

 

[OasisFan79]

The programmer is still under warranty, so if the system plays up again I will switch the programmer for a new one and see if that makes any difference.

Thanks v. much for the replies.