Biasi Garda HE M96.24 SM/B - fault

[Webbins]

Hello there, I'm looking for a solution to the fault with my Biasi boiler and I stumbled across this knowledgeable forum.

The boiler in question (no. N083960604) I have had for the last 7 years and it was around two years ago it began to develop an intermittent fault during a summer when it was not being used much. During winter months, this problem would disappear as the boiler was used more and I would put it to the back of my mind, however now it is becoming more of an issue.

The boiler will fire up when calling for heat or hot water, the fan seems to be spinning, but then will lock out after five or so seconds. The left and right front panel lights will flash green but the middle light remains a solid red. As I say, previously a push of the reset button would remedy this but less so now.

I called out a local gas engineer, virtually a neighbour, and he considered the problem to be either the fan or the air pressure switch. Leaving it to me I said replace the cheapest part (APS) as I wanted an RF thermostat fitting too. This seemed to do the trick for the remainder of the day, but as he said, the exposure to fresh air may bias it, and sure enough the next day starting from cold, the same issue.

I just wanted a second opinion before I proceed with another call out as I'd rather not chuck money if it's not going to do the job as things are tight, don't let the luxury of an RF thermo fool you. The manual seems to suggest the full sequence ignition device may be at fault although I gather manuals aren't gospel.

I had the cover of myself the weekend just gone to have another closer look at the fan, and it seems to rotate without resistance, the Venturi is clear. I replaced it and after covering up again I was able to get a steaming bath full of hot water with no bother. Again mindful of my engineer's advice about the fresh air, the next day I was greeted with the lock out issue, does this point to the fan?

Apologies for the ramble but I wanted to give as much detail as possible, thanks in advance to any advice.

 

[Agile]

Oh dear!

You have opened the sealed combustion chamber which DIYers are not advised to enter.

The correct advice is to call a gas reg engineer to come and check it for safety.

Being a June 2004 manufacture boiler, it will have two PCBs and I am expecting the right hand ignition one to have become intermittent.

Later boilers had a single PCB.

Tony Glazier

 

[Webbins]

Hi Tony, thanks for your reply.

I understand your concern but I wouldn't blunder into something like this and was very thorough in my work, I wanted to just inspect the fan ahead of any further call outs.

What you say does seem to point to the problem, and the behaviour of the boiler seems to be more circuitry than mechanical, is there a test an engineer would do to be sure the ignition PCB is at fault? Also, why would exposure to air after removing and replacing the cover suddenly give life to the boiler?

Thanks again, I appreciate your advice.

 

[Agile]

Any engineer is expected to be able to diagnose faults.

But the reality is that many are not very hot on diagnostic testing and prefer to just swap parts.

I know what you wanted to do with the fan but that is not something we encourage DIYers to be doing on safety grounds.

However, in your case I are fairly sure the faulty PCB is the cause.

BUT, I have not seen your boiler myself and there is only one way to be sure and that is in front of the boiler.

Tony

 

[Webbins]

OK, I got back in touch with my engineer and he replaced the ignition PCB this morning but still no joy, deflating after forking out another £120. Further investigation revealed the chamber was igniting, running for 10 seconds, dying and then reigniting, but the ignition would still keep ticking over, not detecting a flame and then locking out.

He disconnected a sensor that led into the condensate trap, and fired the boiler, it stayed on no problems until he connected the sensor again at which point it would lock out. Pointing towards the trap, he cleared this out as it was blocked with grit and even when connecting the sensor again, boiler was firing great guns, so he left it there and we thought the battle was won. However, wouldn't you know it, an hour after he leaves, with the heat on, it starts locking out again.

Could it be the sensor that is the issue? What is this sensor called, condensate sensor?

 

[Agile]

A blocked condensate trap gives a different set of symptoms!

As the water drains or evaporates away over a few hours of non use the next time the boiler will run for 10-20 min before it stops.

A blocked condensate trap is one of the initial checks which any ( proper ) engineer will do when he first opens the boiler cover.

I don't approve of you opening the combustion chamber but you are quite able to disconnect the in line plug/socket leading from the flame detection electrode lead to the condensate trap. If the tray full then it will run OK with the connector off.

Tony

 

[Agile]

He disconnected a sensor that led into the condensate trap, and fired the boiler, it stayed on no problems until he connected the sensor again at which point it would lock out. Pointing towards the trap, he cleared this out as it was blocked with grit and even when connecting the sensor again, boiler was firing great guns, so he left it there and we thought the battle was won. However, wouldn't you know it, an hour after he leaves, with the heat on, it starts locking out again.

What kind of engineer will go to a boiler and mutter the names of some parts when the condensate trap is blocked by grit ???