Biasi RIVA Compact HE M96.28SM/C-Intermittent Firing Problem

[shenque]

Hi there

I know there's a thread on here with a very similar title but my issue is somewhat different.

I have a Biasi RIVA Compact HE M96.28SM/C boiler. When calling for hot water or when the CH is running, the boiler fires up (you can hear the sound) and then the blue flame appears in the viewing window. Temp gauge moves up to around 60, and the pressure rises too. Hot water comes out the tap, the radiators start to get warm - all good.

BUT - after about 10 seconds the flame disappears. This means that the hot water is not constant, it keeps dropping out and going cold, and also that the radiators just don't get as hot as they should, so my flat is still quite cold even after running the CH all day! It usually happens when then temp needle goes over 60, but the pressure rises as normal and remains steady after it reaches around 1.5 bar.

I am sure I can hear a click when the flame switches off, so don't know if this is a PCB thing or something else. After the temp needle returns to just under 30 it ignites again, blue flame appears, and we go through the whole thing all over again.

Can anyone help? We have wooden floors in the flat and it's bloody freezing at the moment!

Thank you.

 

[shenque]

Hmm I just saw this thread:

//www.diynot.com/forums/viewtopic.php?t=166311

Wonder if it's a similar issue? But the thread I've linked to doesn't have a resolution!

We also don't have a thermostat in the house (well, there is a VERY old one on the wall but moving it has never made any difference, fairly sure it's not connected to the system anymore).

 

[transam]

If I remember correctly the M96 28sm/c , is not your boiler fairly new , under warranty ?


There are 2 temp ntcs on this model , hw & ch all ultimately under the control of the main control board eg this reads & acts upon the info given to it from the ntcs , there is a 3rd temp probe ( excluding high limit stat )
In the flue again an ntc , providing over heat protection for the plastic flue
this ntc can trim the temp of the boiler , or dependant on temp lock it out !

There is a current or X ? Biasi agent on this forum , who may pick up on this thread ?

 

[shenque]

If I remember correctly the M96 28sm/c , is not your boiler fairly new , under warranty ?

Sadly no - have lived in our flat nearly 3 years and it wasn't new when we got there!

There are 2 temp ntcs on this model , hw & ch all ultimately under the control of the main control board eg this reads & acts upon the info given to it from the ntcs , there is a 3rd temp probe ( excluding high limit stat )
In the flue again an ntc , providing over heat protection for the plastic flue
this ntc can trim the temp of the boiler , or dependant on temp lock it out !

Thanks - will try and take a look but that might be beyond me...

There is a current or X ? Biasi agent on this forum , who may pick up on this thread ?

Do you mean Tony (Agile)? I've seen him give some really useful replies on other threads and hoping he can help here!

 

[Agile]

I have just been talking to a tenant with that model which was 1995 so yours is probably about the same age.

Unfortunately, without further information is could be just about anything.

A clue would be given by what the lights show when it goes off.

Tony

 

[mmscaer]

turn the control knobs (C/H & HW) and see if you can feel them turn. have had a couple in the past with broken spindles that attach the knobs to pcb.

could may well be the cause as you describe, stats set at 60 C.

 

[Agile]

Its usually only the right selector knob spindle which is broken by heavy handed builders etc.

But in this case the boiler cuts out after a short time so it will be another fault.

To test the right spindle turn to the off position and see if the LH light flashes every four seconds.

Tony

 

[Slugbabydotcom]

Suspect no1 is CH thermistor

IIRC this boiler started production about 2004/5 and is the same as the ideal mini he and eurocombi

The predecessor was the m90 series with the snapping control knob spindles