Biasi 24s cutting out intermittently

[mrcrusty]

Hello all, I have a biasi 24s boiler that cuts out intermittently.
There is no thermal cut out, and no error light.
Sometimes the boiler will run for days before this happens,other times it may just run for an hour or so. It seems to happen more often when the boiler is working hard ie. when its cold - at the mo its winter!
When it cuts out the pump is still running, just no flame.
WHen u turn on taps u can hear the diverter actuating, but just not igniting the flame.
Over the last couple of years i have done the following work:
Diverter valve full refurb kit (to cure previous fault of no hw)
Flushed out whole system
Taken exchangers off and flushed out (with formic acid)
replaced temp sensors (electronc ones)
replaced psv
replaced gas valve - this was done by myself with guidance from ex corgi reg friend, but was never adjusted or tweaked once installed.
Could the gas valve need properly adjusting or another fault perhaps?
any ideas?

Its Damn cold and if it cuts out mid shower again I'm gonna rip the bugger off the wall!

ps. Made redundant recently and no money to pay an engineer
pps. I am a electrnics technician and can turn my hand to most tasks, and after all the work already done on this boiler don't regard myself as a novice!

 

[transam]

From what u say I assume that u have the biasi boiler with the 3 diagnostic lights , 2 of which may not be visible unless u remove the electrical control cover ? are they flashing in a particular sequence ?

 

[barryauid]

Sounds like the only thing apart from the air pressure switch and psb have been changed so why dont you check the position of the air pressure switch?

 

[mrcrusty]

From what u say I assume that u have the biasi boiler with the 3 diagnostic lights , 2 of which may not be visible unless u remove the electrical control cover ? are they flashing in a particular sequence ?

there is only a green on led, no other lights apart from the red trip neon.

I have noticed however that when the boiler cuts out, the green led seems only slightly lit, and once the boiler is turned of for 10+ seconds then back on, the led is fully lit.

 

[mrcrusty]

Sounds like the only thing apart from the air pressure switch and psb have been changed so why dont you check the position of the air pressure switch?

the air pressure switch seems to function correctly.

When the boiler cuts out, there is no fan running thus the pressure switch wouldn't work

 

[mrcrusty]

just to say, when the boiler cuts out, you have to kill power for at least 10 seconds for the boiler to reset and work again

 

[Agile]

Whilst I will not give you advice on gas matters you can see what the diagnostic lights show as the fault.

Whenever a gas valve is changed it should be set up correctly. This needs a gas registered person who knows how to set it as not all seem able to do it.

Look up my recent posts where I have explained how to put the boiler into permanent diagnostic mode.

For a few seconds you can get this by putting DIP switch 4 down and then up again.

Tony

 

[mrcrusty]

Whilst I will not give you advice on gas matters you can see what the diagnostic lights show as the fault.

Whenever a gas valve is changed it should be set up correctly. This needs a gas registered person who knows how to set it as not all seem able to do it.

Look up my recent posts where I have explained how to put the boiler into permanent diagnostic mode.

For a few seconds you can get this by putting DIP switch 4 down and then up again.

Tony

Thanks for your reply, i have not been on here for a while, but I do still have the problem - it only happens when the boiler has to wrok hard, then it will cut out - not nice when in the shower!
As for the diagnostic you mentioned, well the boiler is a '98 model and only has 1 green led light on the pcb, so am unsure how to get diagnostics,

 

[ChrisR]

I think Tony's thinking of a different Biasi 24S. You mean this one?

Does it always restart straight away (given 10 seconds off)?
If you just leave it , with no call for heat/hot water, does it start up again by itself?

 

[mrcrusty]

Hi - yes thats the bad boy! It will reset straight away after turning off for a while, but sometimes it will cut out agin very quickly, its like a temp related issue, but it doesn't ever thermal cut out.
I notice when it cuts out, the green LED on the pcb goes very dim also,
I have changed one of the temp sensors on the diverter valve assy, but not the other. I did have a problem where the diverter valve assy pretty much melted inside, but i replaced the whole assy with a kit, and flushed the whole system out, and also took off the exchanger and flushed that out too.
I also had a problem with the salmson water pump - the rotor came off - I simply took it out and epoxied it - been fine since, but i do wonder if the pump may have seen better days (very expensive to source another) I know these boilers either came with a salmson pump or a myson cp53 pump. ANy idea if these are interchangeable?
If so I'd rather pay 30quid for a myson rather than over 100 for a salmson

 

[mrcrusty]

and when it cuts out, you have to turn power on and off, it wont restart itself - i would use the timer for this, so it turns off for a coupoe of times a day but it doesn't work - and they aint cheap either!

 

[transam]

So you have got one of the Prisma , early riva biasi???????

 

[Agile]

I totally disapprove of DIYers who change gas valves and particularly when they are not checked or set up.

This is a very dangerous person and in my view no one here should be giving him any advice.

He must have already spent more than the cost of getting a professional would have charged and its still not working and may be dangerous.

Tony

 

[transam]

I totally disapprove of DIYers who change gas valves and particularly when they are not checked or set up.

This is a very dangerous person and in my view no one here should be giving him any advice.

He must have already spent more than the cost of getting a professional would have charged and its still not working and may be dangerous.

Tony[/quote

Good point , I need to engage brain before posting !!! have edited post

 

[mrcrusty]

I totally disapprove of DIYers who change gas valves and particularly when they are not checked or set up.

This is a very dangerous person and in my view no one here should be giving him any advice.

He must have already spent more than the cost of getting a professional would have charged and its still not working and may be dangerous.

Tony

Well thats your opinion, advice or not I will be doing the work myself as I have no money due to redundancy.
I agree perhaps i should have not replaced the gas valve, but i did so with guidance from an ex corgi reg'd friend - and this was done over 3yrs ago due to the original failing.
As for spending more than getting a professional - all the work i have done was not to cure the cutting out problem, merely work to keep the boiler going over the last 7 yrs, since it was a second hand boiler install.
These boilers were cheap boilers and are not the most reliable, and need repair and preventative maintenance.
I did call an engineer to look at the boiler, and he was clueless, but did not charge me for his time thankfully, and so i summize there are a lot of boiler engineers out there who's qualifications are not worth the paper they're written on.
Seeing as I'm an electronics technician, my next step was the pcb - and thats the route I'll go down next, checking solder joints, resistors, regulators etc. and give it a good refurb.
Before i did this i just thought I'd post on here to see if there was anyone with experience of these boilers who may be able to help or point me in the right direction.
so thanks all for your help and AGILE you can call me Mr Dangerous if you like, I can live with that, I've been called worse!