Riello burner locks out after short purge time

[ngate]

My faithful Riello 502T5K, installed 20 year ago, suddenly started to lock out intermittently. It took me a while to realise that there was a pattern to the failures:

Starting with an unlit lockout button the motor would run for a very short period (5 seconds or so) and then lockout. Pressing the button immediately would then produce no response, but with persistence and another couple of presses, the motor would, eventually, restart. This time, moreover it would run for the usual 10-15sec and the burner would fire successfully.

Once the burner was warm, the burner would continue to function normally for the rest of the day. But then the above pattern would be seen when starting from cold the next day.

Can anyone suggest what might be going wrong?

 

[oilhead]

Possible faulty solenoid coil or maybe capacitor. Is there a hum from the motor when first switched on?

 

[ngate]

The fan motor appears to start normally with just the normal "purging" noise. Could there be an intermittent fault in the control box?

 

[oilhead]

There is always that possibility, and persistent attempts at reset will not have helped it. My first suspicion would be the solenoid coil as the box looks for circuits in the startup period, and if there is a problem there, this is how it could show up.

 

[ngate]

Thanks for the heads-up re the coil, oilhead. I pulled it out and tested it for continuity - found 100 ohm resistance, so assume that it's still healthy. But also found that the nut holding the coil in place was loose, so tightened that.

Anyway, while all this was going on I found time to pull the trays out of the boiler itself and gave everything a good clean. Everything looked good, which was quite a surprise given that this was the first time anybody had looked inside there in 20 years. I also took the housing off the burner's fan and hoovered that out, and dismantled and cleaned the oil filter - again both very clean.

But finally, the good new. Having put everything back together and crossed fingers, toes and everything else I gave the burner a quick test. It worked perfectly and has continued to do so ever since

I think the lesson I take from this is that I need to be a bit more diligent about annual maintenance. Just to complete the story, prior to my creating this thread, I'd already realised that the boiler needed investment and had cleaned the blast tube, set the electrode gap and fitted a new nozzle. None of this had made any difference. But clearly /something/ I did subsequently did the trick. I wonder what it was...

 

[Johntheo5]

Is it a Riello G5X Burner like in my 19 year old Firebird 90S, if so, a really outstanding burner, mine has never tripped on combustion failure during this time, new nozzle every 3 years or so and boiler baffles cleaned, kerosene fuelled.

 

[ngate]

Riello 502T5K burner, Johntheo5

 

[oilhead]

Glad to hear the finish.
When any of us offer advice about regular servicing we are often shouted down, but this proves the case. Although you say everything is clean, this is not necessarily a good thing . It can be a symptom of lean mixture, which could explain your original problem when allied to some other factor in the process.