Biasi boiler cutting out..

[Calmore]

We have a Biasi 24S boiler.

Central heating works. Hot water works. Try and draw hot water when the central heating is running and it often cuts out.

(Lamp in the front flashes at double speed; power cycle the boiler and it works OK until next time)

Any thoughts? I have been though the fault finding chart and tested lots of parts but I'm now running out of ideas.

 

[Agile]

Is this really a 24S Biasi at least 22 years old?

If so has it ever been properly serviced?

 

[Calmore]

Hi, I'm not sure it's quite that old. It's a Riva M90 24S which I think dates from just before condensing combis came in. I think the serial number features the date so I can check.

It has been semi regularly serviced; average every two or three years at a guess. Radiators have been flushed, fernox etc added and one of those magnetic filters installed maybe five years back. Radiators get hot with no cold spots.

There's nothing really wrong with it. I mean I know it doesn't work at the moment, but its in v good condition, nothing leaks and many parts have been replaced over the years.

In the absence of any other ideas...

I'm pretty sure all the evidence points towards the boiler overheating and cutting out, but it's getting to the bottom of exactly why is the issue. Sensors have been checked, diverter valve checked along with lots of other parts including the pressure vessel and heatex.

Are pumps prone to intermittent running? It obviously functions OK when the boiler is running, but if it failed to start up occasionally I think there would be no overrun and thus the boiler would stop.

Would a bypass valve being stuck open cause an overheat situation when the boiler is under load.

 

[Agile]

That is what I expected as the 24S does not have any green flashing lights.

However my expectation is that is probably a combustion setting problem which we cannot give advice about except to Gas Registered people.

 

[Calmore]

Checked and the first service sticker is 2005, so it is indeed getting on a bit.

Why would a combustion setting change? I don't remember the fault chart listing combustion as an issue. Is it a common problem on these boilers?

 

[Agile]

The previous 24S boiler was much more reliable and probably one of the most reliable boilers ever made.

Your M90 was not as reliable and perhaps just an average reliability.

The rapid flashing can be caused by several different reasons and to diagnose the cause it would be necessary to check every function of the boiler. The combustion settings can drift over time as components age and thermally cycle. They should be checked and reset every time the boiler is serviced which would usually be advised to be every year. One I went to last week had drifted about 15% too high within about a year.

I expect that you are likely to need a competent boiler engineer.