Isar m30100 - intermittent performance

[2020JimboJones]

Can anyone help me here please?

My Ideal Isar m30100 has started to work on and off, i.e. hot water will last for a few seconds, then go off for a while, then on again for a bit and so on.

I've tried to reset the system which seemed to work for a few days but now I have the same problem again and can't remedy it. The pressure looks quite low (less than one bar) so I've switched the system off in case this could be a water leak but this wouldn't have been fixed by a reset previously would it?

Any help would really be appreciated.

Thanks

Jim

 

[PEDANTICVINDICTIVEMAN]

Sounds like clogged DHW plated heat exchanger.

 

[dereknoble]

Sounds like clogged DHW plated heat exchanger.

2020JimboJones, did this work? I have the same problem.

Intermittent DHW, when I turn on the hot water the pump and boiler fires up and the water initially gets hot but after a few seconds the boiler light goes off, the pump sounds like it switches off and the water goes cold. this is sometimes followed by the pumpo and boiler coming back on for a while (10-20 secs).
Does this sound likely to be a heat exchanger? I have changed one of these before (well, gas fitter has) when it got scaled up but the symptoms were the that the hot water reduced to a trickle, not these symptoms.