Potterton Promax - hot water but no heating

[lasto]

Seeing a Potterton Promax 28 combi boiler where the heating seems to have completely stopped working this afternoon. It is still heating hot water on demand perfectly well.

The hot water indicator on the boiler itself is constantly on, and the burner indicator lights up when I increase the hot water temperature on the boiler. This is true even when there is no hot water tap or shower on in the house. I've tried overriding the mechanical timer to make sure heating should be demanded, but it refuses to kick in. The pressure reading at the boiler is between 1 and 1.5 bar.

Does it sound like an obvious fault?

 

[DP]

Have you checked for a leak on hot water supply pipe? That could be the issue

 

[CBW]

Sounds like the flow sensor cartridge is stuck open with the indicator being on constantly. If you do want heating over hot water, remove the boiler cover (if it doesn’t form part of the combustion circuit) and remove the Hall effect sensor.

 

[lasto]

Have you checked for a leak on hot water supply pipe? That could be the issue

As far as possible, no obviously leaks. I thought it might be an open tap or minimally dripping shower, but no.

Sounds like the flow sensor cartridge is stuck open with the indicator being on constantly. If you do want heating over hot water, remove the boiler cover (if it doesn’t form part of the combustion circuit) and remove the Hall effect sensor.

Happily, the neighbour I was trying to help called me back to say that the heating was back on again. Looking at the boiler again, the hot water indicator had gone out and let the heating come on as it should, though I've no idea as to why there was such a delay.

My neighbour is very elderly and understandably scared of being cold, and even opening the boiler cover is beyond what I'd want to attempt. As she is a vulnerable customer, an engineer will be out tomorrow morning to check it out and hopefully give her some peace of mind that it won't happen again over the winter.