Intermittent Oil Burner Lock Out

[Alfiromeo]

Oh this is getting tedious!

Having read reams and reams on the subject of intermittent oil burner problems I THOUGHT I had narrowed my problem down.

I found that the capacitor on the motor had leaked a small quantity of waxy substance which I imagined would signify it was giving up the ghost. I wasn't able to buy a direct replacement from my usual supplier of heating parts and, in the end, bought a motor start capacitor from Maplins. Correct specification etc (but plastic bodied rather than aluminium). It says it's Ok up to 85 degrees C and is 3uf rated....just like the one I replaced.

All has been well for a week. Then, when I was just beginning to think it was a solved case....bang....another lockout.

It started immediately I pressed reset and has gone fine since.

I have done all usual service items. Namely, new nozzle, cleaning chamber, filter on tank outlet (which was quite grubby & I did that today), electrodes (cleaning and resetting).

I'm now wondering if it's the solenoid on the pump. Or the transformer....although the spark looks great. OR.......could it be the capacitor from Maplins. £3 instead of an expected £12?? A capacitor's a capacitor isn't it??

I have never actually managed to witness a lockout. So no clues there.

HELP???

Jim

Oh yes, it's a Sterling 40 ST108PL burner. 8 years old.

 

[gremlin16]

I'm now wondering if it's the solenoid on the pump

More than likely.

Might be worth checking, pump pressure, and checking and setting combustion values.

 

[Burnerman]

As above - the capacitor starts the motor spinning so its unlikely to be that.
Has your system had a pressure and flue gas analysis check recently?
Particularly important if you have a balanced flue.
John

 

[Alfiromeo]

It's a conventional flue. A gas analysis check has not been done recently. Could a rogue value cause this type of problem or are you both thinking the pump solenoid is more likely? I gather the whole thing can break down slowly but surely and was advised by Danfoss that they can be troublesome at any point.

 

[gremlin16]

Has your system had a pressure and flue gas analysis check recently?

That would mean the OP would have to fork out for a FGA, oil pressure kit.

And pay registration and resits.

Bet he (diy,er) ain't got any of the above

Could always phone an OFTEC engineer to sort it out.

 

[Burnerman]

Its absolutely true to say that you can't go any further without a pressure test and FGA - seriously. a smoke test will be done before Mr. Oftec risks his gas analyser.
Settings can't be guessed and incorrect settings will cause smoke, internal condensates, soot deposits or burning out of baffles.
I charge £40 for this, and boy if punters looks could kill then I'd be history

 

[dcawkwell]

The first thing to do is make sure the oil pressure and air mixture
are correct.

As you won't have a flue gas analyser you won't be able to do this.

OFTEC engineer required.

Other possibilities are solenoid and coil.

 

[Alfiromeo]

The baffles, flue and everything would not suggest the boiler has been overfueled. The air/fuel mix was originally done in the old fashioned way (by my Oftec man!) ie, having set the fuel pressure to the correct setting (using a gauge) he decreased the air until smoke appeared and then increased from there bit by bit until it was burning without smoke. He said, when you've been doing it as long as he has you don't need the gas analyser!! Was he giving me some S**T??

Anyway, I can easily be persuaded that getting the analysis done would be in my interests......and therefore that's what I will do.

Meanwhile, finding this intermittent fault is driving me.....and my Oftec man...mad. We can't make it happen. And I can't keep getting him here.

"Other possibilities are solenoid and coil." Where/what is the coil??

Cheers.

 

[spraggo]

Have you checked and cleaned the FFD

 

[dcawkwell]

The coil is the round part that fits onto the solenoid of the fuel pump.

Could be either the solenoid valve is sticking or the solenoid is beginning
to fail. Both can happen once the boiler is getting hot so you get a failure intermittently.

 

[Alfiromeo]

FFD being the photocell? Yes. Cleaned it. How would you check if it works faultlessly? Good idea just to replace?

 

[Burnerman]

The baffles, flue and everything would not suggest the boiler has been overfueled. The air/fuel mix was originally done in the old fashioned way (by my Oftec man!) ie, having set the fuel pressure to the correct setting (using a gauge) he decreased the air until smoke appeared and then increased from there bit by bit until it was burning without smoke. He said, when you've been doing it as long as he has you don't need the gas analyser!! Was he giving me some S**T??

Anyway, I can easily be persuaded that getting the analysis done would be in my interests......and therefore that's what I will do.

Meanwhile, finding this intermittent fault is driving me.....and my Oftec man...mad. We can't make it happen. And I can't keep getting him here.

"Other possibilities are solenoid and coil." Where/what is the coil??

Cheers.

To be fair you can get a reasonable idea if the burner is happy but a proper FGA is essential.
As it happens I always keep the Danfoss coil in stock - I've never had such an intermittent fail - sure they go once the burner starts to get hot but never once in a blue moon.
John

 

[Boilerman2]

Yuo definately need to get a Service Guy or Gal in!!
you could waste a fortune "Guestimating" a fault on a Bentone Sterling!!
many possibilites - you don't say what make of boiler it is fitted to but could be Control box, Photocell, Ignition Transformer (EBI) or even a flat spot on the motor the cost of fitting these parts without firm evidence would cost far more thatn a Proffessional engineers visit!!

 

[Alfiromeo]

Spoke to Danfoss today having taken the fuel pump off. The shaft was a little on stiff side to turn and there was a slight squeak too. That's now been replaced along with the solenoid. And yes, the pressure has been set etc.

Incidentally, how hot should the solenoid get? I was surprised at the heat but the new one is just the same.

 

[Boilerman2]

Solenoid coil operating temperature??? Too hot to touch!!

P.S. you have set the oil pressure, (I assume to the same pressure as the old pump?) - BUT what about the Co2, O2 and CO all of these should be tested and optimised to suit the boiler - once again what model boiler do you have??