Ariston Microgenus 23 cutting out (and sparks constantly)

[mjjstorey]

Hi,

New on here (and to owning a house so taking care of a boiler).

I have a Ariston Microgenus 23 which keeps cutting out (with the red ignition fail light coming on so I have to reset). I have not really taken any notice of it before and was always used to dealing with my parents boiler which had a pilot light.

It cuts out randomly - can work for 30 mins and heat the house, or cut off after 1 minute.

Something I have noticed (didnt notice before because it just worked) is that it sparks constantly even when it is lit and 'running fine'.

Main question is whether it is meant to spark constantly? Looked all over the net and cannot find an answer.

At a guess if its not meant to be sparking all the time then its going to be the PCB. If anyone can assist it would be great, I am an IT technician by trade so I have a reasonable understanding of circuit boards and have done the usual basic checks.

Thanks in advance.

 

[Dan Robinson]

Check that the polarity for the boiler is correct first and foremost.

 

[mjjstorey]

its been working fine for 2 years, so pretty sure it is, electrics in the house have not been touched for over 6 months (even lightbulbs!) , etc and it only started playing up this week

 

[Dan Robinson]

It's not meant to spark constantly (hence the polarity question)... When was it last serviced (your solicitor/you should have asked for all that information as part of the sale).

 

[Agile]

It is not meant to spark constantly.

It is meant to recognise the flame and stop sparking.

We cannot give advice on DIY gas repairs and there are some possibilities which are not the PCB. Obviously at the boiler I would check those first.

But statistically its most likely to be the PCB and they dont seem very reliable on that model.

All you can do is check the integrity of the electrode connection to the PCB and then replace the PCB. At over £100 its not cheap.

There is a high value resistor in series with sending circuit on the LV side of the EHT transformer and you could check they are not high resistance and the decoupling caps are not low resistance etc.

But as my advice must be to call a gas registered engineer, if its not the PCB then dont blame me!

Tony

 

[mjjstorey]

Cheers for the confirmation on the constant sparking, it did seem a little weird (then again, never seen one without a pilot light before).
House was a repossession so there was very little information, I would guess quite a while though.

 

[mjjstorey]

Thanks for the comments agile, very useful. Think I will def have to call in the cavalry on this one

There was nothing visibly wrong with anything on the pcb when I inspected earlier, but as the boards are so complicated and half of the bits are sealed its not even worth trying to look at it. Lets hope one of my mates is still gas safe'd up

 

[mjjstorey]

Just looking over the comments and this one is purely out of interest, how does the detection electrode actually detect there is a flame, I understand the theory behind a thermocoupler, but the electrode only has a single core and common sense would say that the only way to detect presence is through heat which would melt the cable / pcb.

 

[ChrisOxford]

Probably flame rectification. Google it. Very elegant way of doing things

 

[Dan Robinson]

As long as you have correct polarity .

 

[ChrisOxford]

Good point. When my boiler was fitted in 1993, the (Corgi reg'd) installer couldn't get it to fire up.

A man from Worcester had to be summoned... and found he'd connected L & N backwards in the fused connector unit. All was well when that was corrected.

A modern boiler is one of the very few domestic electrical appliances that "cares" about this, though there are many that are less safe when wired backwards.

 

[Agile]

Oddly perhaps the makers seem to be designing out that feature!

Nupty springs to mind to describe your installer.

In fact it embarasses me to work in the same industry as those who have to call someone else because they lack the most basic skill!

 

[Dan Robinson]

Went to one today where the wireless room stat receiver was wired in the FEED side of the plug socket feeding the boiler's plug

Only knew it was thus because last time I worked on that boiler the damn thing lit up for heating even though the boiler had been unplugged.

Could have been nasty otherwise.

 

[mjjstorey]

wow! I got taught basic home electrics in a-level physics, surely its a requirement for fitting boilers.

I checked on the polarity and the circuit board has a L and N symbol next to the power in, checked that the plug was wired correctly too just in case

Sat down this evening with a neighbour (plumber / builder) and the wiring diagram for the boiler and started narrowing things down. Worked out from what was turning on at certain points that its either a relay, small chip or the main chip that is faulty, so fingers crossed the pcb that is on its way will sort it.

ChrisOxford - thanks so much for recommending to look up flame rectification, makes a lot more sense now. Checked the cable for continuity and when its on there is a very tiny blip on the amp meter (min reading is 0.5 mili-amp so far to large to read accurately)

Will let you all know what the outcome is, your help has been awesome with understanding certain bits though

 

[ChrisOxford]

Nupty springs to mind to describe your installer.

To be fair, the installation is one of the neatest I've ever seen and the Worcester guy described it as "textbook" when he saw it.

But by his own admission, he knew absolutely nothing about boiler repair.