The boiler starts up and starts cycling while boilermate control board status shows pump and boiler off

[KanRat]

Hi,

I have a boilermate A-class OV and a baxi solo 3 boiler fitted in my flat. Not sure how old it is, but we moved in 3 years ago and it has worked fine so far. The problem started a couple of weeks back when the hotwater pressure dropped. I called the BG homecare and the engineer came and replaced the heat exchanger. It started working fine, but the same night the boiler stopped working. He came back and replaced the control board on the boiler and the boiler pump and valves on the Boilermate. It seemed to have fixed the problem and everything worked fine until the very same night. We turned off the central heating and went to sleep only to be woken up by a loud banging noise at the boilermate and the boiler. In addition to this the boiler was cycling quite fast. The cycling sequence is like this: The power on light, followed by fan light and pilot light and immediately cuts off and starts again with power on, fan on ... It never reaches burner on and sometimes does not even reach pilot on. I turned off the boiler and switched off the hotwater switch and the green power switch on the Boilermate immediately. The BG engineer came the next day and replaced the control board on the boilermate. Last night the same problem happened again. Before I call BG engineer again, I want to get some advice from this forum.
I have since done some investigation and found the following. When I turn on the boilermate, switch on the hot water, wait until the boilermate control board status shows "boiler on" and "boiler pump on" and then go and turn on the baxi boiler, it all works fine. I can then turn on the central heating switch and it also works fine. It goes wrong when the central heating switch is off, the hotwater switch is on and the Boilermate control board status shows the boiler pump or the boiler are off, but the boiler suddenly starts cycling by itself as explained above (it happens after the boiler has been off for around an hour). I thought the boiler is controlled by Boilermate. How can the boiler try to turn itself on when the status on the boilermate shows neither the boiler pump nor the boiler is on? My suspicion is the new control board change on the boiler, but BG engineer is not buying that. Any idea what could cause this?

[mike]

It would or does sound like the ACB
Is it / has been coded in properly ?
Mike