Biasi M90e 24S intermittent hot water, intermittent fault

[davidmadona80]

Hi,

I have a biasi boiler. Normally it works fine however no hot water after running it for 20-30 mins.
The next time i turn the tap on, its cold. I have to wait for 5-10 minutes before it works again.

No lockout. No indicators.
Only indicator it gives is fast light pulses when it can't turn on.

Any idea what this could be, as this boiler has new dhv temperature probe, dv membrane, switches etc.

Thank you.

 

[jj4091]

Does the boiler run the heating and hot water. If so do the radiators or pipes to them heat up when you have the hot water running. If that is the case pe§rhaps you have a problem with the boiler diverter or zone valves if that is how your system works.

 

[davidmadona80]

Yes, they both works separately and together if ch called during dhw or vice versa during normal op.
The problem is observed mostly during dhw operation ( in mornings when demand is high) after continously running for long time. Its a combi boiler and i have no external zones or anything if that's any helpful.

 

[CountryFan]

Have a check for a crossing mixer.

 

[jj4091]

Yes, they both works separately and together if ch called during dhw or vice versa during normal op.
The problem is observed mostly during dhw operation ( in mornings when demand is high) after continously running for long time. Its a combi boiler and i have no external zones or anything if that's any helpful.

As I said, next time it happens check the flow and return pipes that go to the heating they should not be hot if you are only calling for hot water and the heating is off. If they are then possibly a diverter valve problem.

 

[davidmadona80]

As I said, next time it happens check the flow and return pipes that go to the heating they should not be hot if you are only calling for hot water and the heating is off. If they are then possibly a diverter valve problem.

Spot on, they are littel warm both at inlet/outlet straight out of boiler, as i go further down thr pipe from boiler not so. However after 5-10 mins, they are cold again. When i call boiler dhw again, it runs some sort of cycle, no spark, then it turns off and restarts thr cycle and suddenly there is a flame and hot water.