Trianco Oil Boiler start-up

[JeremyB]

Thanks again for all the helpful comments. Point taken about getting someone in to do a smoke test and FGA reading.

Yes, I do have a Tiger Loop. Regarding good suggestions about oil pressure at point of loss of flame (I will test this), dodgy drive key, slipping pump coupling, weak secondary coil, etc, wouldn't these things continue to cause a problem once the boiler has warmed up?

I don't think it's the balanced flue circulating the flue gases. The original flue started to cause this problem some years ago and I replaced it. As a test, removing the air intake hose to the burner does not improve the problem.

I am wondering if the prolonged wet weather could be behind the problem. The boiler is located in a garage with a single skin brick wall. It has a low-level rear discharge balanced flue with a total distance of only around 60 cm from the airbox to the outer end of the flue. Is it possible that driving rain has been entering the apertures into the incoming air part of the flue and lying in the flue, causing there to be heavily moisturised air going into the burner at the start of ignition after a period of non-operation. After repeated stop-starts things would dry out a bit and the boiler would run correctly. This is me going out on a limb a bit, but I do wonder. It's worth noting that there is a slight fall on the flue from the airbox to the outer end. J.

 

[SJB060685]

Like I said you could potentially rule out some I mentioned as like you say you'd expect it to be a constant fault.
Removing the hose for air intake is how you would check, I would also stick a FGA in.
The reason I ask about tigerloop was when I thought you said you were running at 70psi I was thinking the loop might be helping. The tigerloop or any deaerator not only lifts fuel and removes air it also helps warm the fuel through it circulating through pump and back by friction when at pump max capacity. If you were running on too low a pressure then this pre heating might result in what's happening.
Your theory about the flue is a sound one, however if you had saturated air then I would expect it to burn inappropriately, ie sooting etc. What are the flue gases like during the initial period?
I have known pump drive keys and couplings to cause this before they completely go altogether, I'm not saying this is the cause but checking pressure at point of flame failure will give you a good idea.

 

[John.g]

I have seen this problem on three Riello G5x burners, on one, replacing the nozzle cured it, on the other two, replacing the photocell cured it.

 

[JeremyB]

Thanks SJB060685 and John.g. It looks like there are a number of things I need to check out. I'll come back here in a few days and report. J.

 

[John.g]

I can see JeremyB posted 29 minutes ago looking at the thread starter but no message appears here.

 

[SimonG]

I can see JeremyB posted 29 minutes ago looking at the thread starter but no message appears here.

See this a lot, newbies posts need to be approved before they appear but the system still let's you know there's a response even though you can't see it until it's approved.

 

[JeremyB]

I may have identified the problem. During the very wet weather while the boiler was inoperative for a number of hours, rain would have been entering the air intake in the balanced flue. It seems possible that when the boiler fired up there was heavily moisturised air being drawn in and this caused the problem of establishing a flame.

I was able to do a test yesterday having been out for 7 hours with the boiler not operating. In the past it would have had a problem establishing a flame but everything was OK. I think this is because we've had 3 days without rain. Time will tell! J.

 

[SimonG]

Fingers crossed, would be interesting if you could come back and let us know as I have never seen that before.