Biasi 24 locks out!!

[midnite]

Sorry for the essay...

Came to turn the tap on a couple of weeks back and no hot water. Went to the boiler, it was locked out. Pressed the little red button and the boiler fired up ok only to lock out 5 or so seconds later. It keeps doing this, 5 seconds and it locks. It also keeps the ignitor going right up until it cuts out. The boiler will not stay on. Seems to me like the flame isn't being detected.

I changed the detection electrode and aligned it exactly as the old one and as per manual. No joy. I have a corgi friend who got hold of an ignition sequence board for me and told me it was easy to fit. The fault is still there. I am an electronics engineer and I have gone over the old board. No fault that I could see, maybe a leaky diode, but the new board would have cured the fault if that was the case. Checked connections, looked for dry joints, none.

The pump is working fine, the fan and air pressure switch are working ok (boiler firing up). Turn on the hot water the boiler fires up and the pipe just manges to get warm before the boiler shuts off. CH does the same, pipe gets warm and then shut off.

I'm stumped and my corgi mate is sunning himself in Florida for three weeks and I need this fixed. If I need to pay an engineer then so be it, but I was hoping you guys might have some ideas as to where the fault might be. Any help would be appreciated.

 

[Slugbabydotcom]

Edited:- After slight misinterpretation

Seems your boiler is lighting but then goes out. I'm not there with my kit to check your CH thermistor. Quite a common thing on these in my experience. Especially after a DIY or cowboy install where the system isn't properly flushed.

FOR TESTING PURPOSES ONLY
Swap the leads over if you can OR
Stick say a 10k resistor across CH thermistor wires.

Have you checked the obvious? ie. The pressure is up to 1- 1.5 bar?

After that the spark gap should be about the thickness of a £2 coin away from burner.

Then you need your corgi friend to check that lighting pressure is up to the mark.

Is the flue intact and as per the manufacturers instructions

Is the flame lifting off the burner and seeking air? Possibly indicating a fan or again flue problem.

Have you checked the polarity of the power supply?

 

[midnite]

Thanks for responding.

Seems your boiler is lighting but then goes out. I'm not there with my kit to check your CH thermistor. Quite a common thing on these in my experience. Especially after a DIY or cowboy install where the system isn't properly flushed.

This may be misinterpretation but the system was installed by a company called Gas Flair 2 years ago and it was power flushed. Something else was put into the system to help protect the boiler, can't remember what it was called.

FOR TESTING PURPOSES ONLY
Swap the leads over if you can OR
Stick say a 10k resistor across CH thermistor wires.

Both DHW and CH thermistors are fine, 16K across each. Disconnection of either stops the boiler from firing up.

Have you checked the obvious? ie. The pressure is up to 1- 1.5 bar?

Approx 1.2 bar.

After that the spark gap should be about the thickness of a £2 coin away from burner.

4mm gap, 10mm from burner as per service manual.

Then you need your corgi friend to check that lighting pressure is up to the mark.

Can't wait 3 weeks. Looks like I will have to call out an engineer after all. Any opinions on British Gas?

Is the flue intact and as per the manufacturers instructions

Is the flame lifting off the burner and seeking air? Possibly indicating a fan or again flue problem.

Gas Flair fitted it so it should be. It has been working for the past 2 years without a problem. The fan seems to be working ok. Looking through the pilot window and there doesn't appear to be a gap between the flame and the burner.

Have you checked the polarity of the power supply?

The fused spur is wired correctly and so is the boiler.

Just another thing to add(sorry I forgot). The lights on the boiler say no signal from the ignition board. Which is why the detection electrode was suspect and then the PCB.

Once again thanks fro your help. I will call British Gas today unless you have any other ideas of what the problem may be.