ferroli modena 80 locking out

[gezzer28]

Hi, i'm from sheffield. This is my first post and the site was recommended by a gas fitter who called today.

My combi keeps intermittently locking out especially when i have been in the shower for a while. After 5-10 mins the water goes cold and the combi needs resetting. it can work ok when running the hot tap.....

Sods law that when the gas fitter came it worked fine. He checked the gas valve and checked the emissions with his electronic analysis 'whotnot'.

He cleaned some sort of electrode. Any ideas as to the cause of this fault??

Gezz

 

[bengasman]

When is the last time it had a full service?

 

[gezzer28]

About 2 months ago.....funnily enough the problem with lockout after runnning the shower started not long after the service. Coincidence????

 

[bengasman]

Could be a coincidence, but that would be a bit of a coincidence.
Do you know if the whole machine was taken to bits and reassembled?

 

[DP]

How long did the service take and what did you pay?

A service calls for checking clearances and tolerance among other things. Often a service by some is an operation check. A service should be what the manual asks for. Was your work carried out in conjunction with the boiler manual?

 

[gezzer28]

Don't know if anything was removed as i didn't stand over the guy..

Did get a printout which shows me the burner pressure was 11mbar, the co in ppm was 52, the co in percentage was 5.2 and a ratio reading of 0.0005.

Anyone got any ideas as to why the lockout on hotwater running for a while.. I've had my ladder up and checked the flue outside. Looking inside with a torch it looks clear--no blockages..

One forum search suggested changing electrodes and flame sensing electrodes?? Could those be the cause??

 

[undercover]

Can be a temperemental boiler - the modena......

Seems as if it could be the electrode and flame sense electrode. Could be that when the burner gets hot (eg midway through your shower) its loosing rectification and locking out. The electrodes on these models have a habit of warping from the heat which may explain the prob. Looks like your gas fitter tried a temp fix by cleaning and possibly resetting the gap. But i've found that doesn't work.

Time for a new set which i think have now been upgraded.

Hope this helps..

Maybe someone else has another idea to suggest so wait to hear for any further responses.

 

[gezzer28]

any idea of the parts numbers that i need or is this a gas-safe job only

 

[bengasman]

Defo RGI job.

 

[DP]

All you got was a flue analysis. It is not a service. What the printout shows is ratio of gases in the flue products. Boiler could be knacked, but if flame picture (as shown by the printout is OK) it is assumed the boiler is OK as well.

Now I will go and get my tin hat to take shelter under.

 

[bengasman]

that's about right though. FGA only tells you that the fluegasses are clean (or not) when you measure them.
Bit like mot, if brakes, lights etc work, it passes, but could drive just long enough to get to breaker's yard under own steam.

 

[bigelsy]

could I have the same problem?? I have read various reports on the boiler but none seem to match my problem. My boiler trips out after running perfectly, times vary from 30 minutes to a couple hours. I have dropped the pressure in the rads and checked the pressure in the expansion vessel is 1 bar. Re charged the rads & bled pressure back up to 1.1 bar. Seemed to work for longer before tripping. i discovered a brittle air flow sensor in the fan had broken off and dropped in the fan casing. have replaced the plastic tube but could not remove 1 in casing. Heelp! Please!!!! HW works fine & rads get up to temperature and cut off, but boiler still trips out after time.