Any Riello Experts?

BornForDying

I was out on a service call with a Buderus G115 with a Riello F3 a few days ago.

Unit was installed in the late 90s.

Unit was having an intermittent problem as follows:

Would run through pre-purge fine, and light. After 5-10 seconds, the flame would go out, but the motor would continue to run through a pre Purge cycle, after which the burner would re light. This cycle would continue.

Hate to say it, but between the other tech and I, we threw every part at this thing with no luck. Tested everything per Riello troubleshooting guide. Nothing.

Call up Tech support, he says without question, it's an issue with low sulfur fuel oil. Recommended an electrode adjustment, and fuel pressure increase of 20 pounds. Customer hasn't called back yet.

What's the deal here? Anybody have an understanding of why the low sulfur oil causes this problem, and why this fix works?

GW

Hard to believe the oil is to blame but anything is possible

Yes in the old days (your system is Old Days) jacking the pressure was the ticket. Now the G115s come cranked up. Not too many years ago it was set for 150.

Are you lifting oil? Did you check vacuum? Excessive draft? Too much draft pulls the flame off the head

newagedawn

change the strainer

STEVEusaPA

Without knowing the rest of the numbers, I would check for too much air, then ohm out the coil for the fuel pump.
Could also be very cold oil, or something in the fuel line. What was your vacuum number?

BornForDying

No lift on oil system. About 20 ft of 3/8 coated. Dual filtration. No reading on vacuum gauge at spin on filter. Customer has annual cleaning done where filters, strainer, and nozzle are changed. Always nice and clean. System is well taken care of.

According to customer, issues started 6-8 years ago. I found out later NYS mandated the switch to ULSD in 2012.

If the flame was going off on flame sense (lost flame) wouldn't it trip reset? This condition never does.

Coil was within spec. Tried a new one just to be sure. No change in faulty condition.

STEVEusaPA

I've been using/delivering/selling ULSD w/wo bio for at least that long, never had a problem. In fact I think things have improved-heat exchangers cleaner.
I'm disappointed tech support would say it's the fuel, then tell you to adjust the electrodes, jack up the pressure. Did they spec a different nozzle?
What were all your combustion numbers-draft (OF/OB), air/head settings, nozzle, pump pressure?

Jamie Hall

We've had a somewhat similar problem with a Carlin -- prepurge, start, 15 seconds, fuel cutoff. Run through the purge, restart and run just fine. Only did/does it once in a while. Never managed to actually catch it in the act. Never did figure out why...

Robert O'Brien

Flame isn't stable when ignition drops out. Usually over aired or cold oil. Needs to be setup with analyzer

Jamie Hall

Robert O'Brien said:

Flame isn't stable when ignition drops out. Usually over aired or cold oil. Needs to be setup with analyzer

That's what we figured. Been over the whole thing with a fine tooth comb, good analyzer readings (one of the experts on the Wall does that for me). Still puzzled...

EBEBRATT-Ed

Maybe a slight suction leak. Burner lights the first time but has some slight foam or air, shuts off recycles and has solid oil the second time around just a guess.

Maybe check flame signal or cad cell resistance on a cold start and see if it changes when it warms up

rick in Alaska

I bet this is direct vent? The only time I see this happen is with this setup, and a concentric vent. If there is s slight wind, the combustion air intake draws the exhaust right back in, and since the riello responds so well to a lack of flame, it flames out and goes right in to recycle.
If this is the case, all you can do is run separate exhaust and intake lines with better separation on them.
Rick

BornForDying

Chimney vent. FYI, still no call back after the tech support recommended adjustments.