heating only fires when hot water turned off. Ideal Isar HE24

[brandomoron]

Hi
My combi stopped feeding the central heating last week, and only fires for hot water supply when both heating and hot water are both set to ON.
BUT if I turn hot water function off, then the central heating will work.
So I can manually switch between hot water and heating but not have both simultaneously.
If I select both to be on, then it will only heat hot water supply.

Is this a diverter valve problem or microswitch or something else?

A week before the problem started I bled the system a bit to add inhibitor as it had not been added after a previous system drain to change a leaking pressure top up valve. Then pressure topped back up between 1 and 2.

Thanks

 

[SafetyBoots]

Hi

Have you manage to resolve the issue on this boiler?
Got the same problem at the moment, was adviced by ideal to replace hot water thermistor and boiler programmer. Both done, £150 later, same problem.

Many thanks

 

[brandomoron]

We had it on central heating only for a week or so manually switching to hot water just before anyone wanted a shower and then back to central heating.
Then after a week I turned it in and off a few times to double check it still did not work before an engineer visit and it was working fine again.
Engineer said only explanation for the problem is when there is a constant hot water demand situation as the boiler prioritises hot water over heating. Such a situation could be a hot water tap left running which maybe someone had noticed and turned off during the week. Or in your situation, assuming no hot tap fast dripping, could there be a hot water pipe leaking somewhere? However you would notice the boiler intermittently firing to feed it. Mine wasn't. So it was a self resolving mystery...