Ariston Microgenus 31 - Error E33

[Get_Army]

Hi,

My 18 year old Microgenus II 31 is going into E33 when DHW is running with a high flow rate. It is OK with a lower flow rate.

Error E33 means "The air pressure switch is closed before the ignition sequence"

The observed behaviour is that a hot tap is opened fully and the boiler ignites with the digital read out increasing as DHW temp increases up to about 50 deg. The flame then cuts out (flow neon remains lit throughout) and the error code E33 is displayed for a period of 20/30 seconds. The flame then reignites and the error code clears, the DHW temp increases back to about 50 deg whereupon the cycle repeats.

The system runs fine with no errors when the sealed front cover is temporarily removed. The fan seems to spinning freely. The silicone tubes from fan body to APS are clear from any debris and I can blow air through the APS. There doesn't seem to be any obstruction in the flue. I don't have any air pressure sensing equipment to test with.

What would the wisdom of the group suggest? Aging fan needing replacement? Faulty APS? Air flow blockage/restriction that I can't see within the fan body?

I have seen suggestions that the flue restrictor ring can be removed even though the horizontal length of flue is less than 1m? Presumably this just reduces the workload on an aging fan.

Plenty of refurb fans available on Ebay at approx £30 and new fans for approx £100.

Any advice gratefully received.

 

[jeff the gasman]

Sorry, we’re not allowed to give gas advice on here.
A decent gas safe guy will sort that issue easily!

 

[Get_Army]

Fair enough. Actually I think I've solved the issue myself.

I got up the ladder and shone a torch up the flue and the outer part of the concentric pipe (air in) was full of cobwebs and spiders etc.

I have a feather duster on a stick which I trimmed back and used to remove the crud and the problem seems to have gone away. I guess it was acting as a flow restrictor!

Cheers

 

[jeff the gasman]

Fair enough. Actually I think I've solved the issue myself.

I got up the ladder and shone a torch up the flue and the outer part of the concentric pipe (air in) was full of cobwebs and spiders etc.

I have a feather duster on a stick which I trimmed back and used to remove the crud and the problem seems to have gone away. I guess it was acting as a flow restrictor!

Cheers

Well done. You may have hit it in one!