Ferroli Modena 80e troubles...

[calman]

Hi,

Im having trouble with my Modena 80e boiler, it has been tempramental for a while.

Problem is, When cold the boiler operates normally both CH and DHW. It will run for around 10-15 minutes then cuts out. Resetting brings the boiler back on but for around 5-10 seconds.

I have replaced the venturis in the fan, cleaned the fan and flue thouroughly.

On one occasion I turned on the DHW prior to resetting, the boiler remained on for as long as I needed Hot water. After turning off the Hot Water the heating came on perfectly for around 10 minutes then cut out again.

I have swapped plugs on the two thermistors just in case one was faulty, this made no difference.

I have flexed the PCB (safely!), no difference.

Any ideas would be greatly appreciated.

Thanks

Darryl.

 

[superdupergasman]

What about the electrodes?? These lift away from the burner when hot then eventuallly get too far away the the spark is very weak.

Try bending the spark one back untill the gap is about the width of a £1 coin.

A simple suggestion.

 

[calman]

Hi Superdupergasman,

Wow, quick reply!

I have checked the electrodes, assuming the left hand one is the flame electrode and the right hand one the ignition one?

The left is about an inch off the burners which assuming this is the flame sense electrode would be ok at this distance?

The right hand side electrode is about 3mm off the burners and (if it is the ignition) is working fine as the burners light ok.

Ive just had it working flawlessly for 12 minutes! until I turned the CH temp knob from 60 to 70 degrees then it cut out within 10 seconds! Boiler was in standby, then came on, then shut down 10 seconds later.

Is this an overheat problem? It gave the 'feel' that if I'd left the thermostat well alone it would have soldiered on forever.

Prior to the troubles the thermostat has been on 80 degrees.

Hope this helps.

Darryl.

 

[bengasman]

As you have already done the respiration, my thoughts go back to the thermistors. They are pretty cheap, would be worth replacing them. if they are wrong, it is only marginally which makes it very hard to measure.

 

[calman]

Thanks Bengasman,

I will give that a whirl tomorrow.

Darryl.

 

[calman]

Well it is the morning after the night before.

Strange thing happened through the night, we had a half hour power cut!

Power came back on, boiler came back on, it is in our bedroom, hasnt been off since!

Pump runs continuosly, burner comes and goes as it should, Hot water was perfect this morning, radiators toastie.

Is this a miracle boiler or am I being far to optimistic? Perhaps it needs a period of no power at all to reset and calm down?

Prior to the power cut the boiler would light for 5 seconds go off for 5 minutes then back on for 5 seconds off for 5 minutes, and round and round and round!

Curious how a power cut could alter its behaviour in such a massive way!

Any thoughts anybody?

 

[calman]

Well problem is now resolved, replacing both thermistors solved it as per previous suggestions, THANKS!

Im guessing they where underreporting the temperature of the heat exchange thus the boiler was cutting out on its over temp limit switches?

Just a theory but seems plausable.

Hopefully this may help someone else out in the future.

Thanks to all that offered advice, it was greatly appreciated.

Thanks

Darryl.