Yellow spot after soot up

Robert_H

I had a no heat call tonight that turned out to be a soot up. Buderus G115WS/3 with a Riello. It had been cleaned by someone last month and now was caked with Nice (if soot can be nice) soft soot.

After cleaning I checked pump pressure which was at 150 and I adjusted it to 185(spec) it had a 75-60A which I replaced with a 55-60A. I also set the air band and head position to spec for starters.

MFR	Buderus
model	G115WS/3
Burner	Riello
nozzle	55-60A
Pump Pres	185
Head, static plate	1
Firing Rate	= 0.75
Draft Breach
Draft OF	0.03
Tstack	612
O2	5.2
CO	99
CO AF	= 132
EFF	79
ExAir	31
CO2	11.8
AT	53
Net Stack	559
Comment	yellow spot

I had to push the head forward to "1" to get the CO to drop (spec is 2)

The CO readings are dropping, and are Post Soot up so I feel they will continue to drop.

I pulled yellow spot on every smoke test I did, that and the High net stack temps tells me high excess air yet, Excess air is a little low for what I usually end up with at a final reading. O2 and CO2 are reasonable.

The head is clean and when I had the door open I pulled the gun and really cleaned the tube and especially the venturi area with a brush and rag. So I don't think there is an impingement issue.

I don't get yellow on the smoke test very often and the few times I have it was confirmed with high excess air. but not the case here.

Ill be back to check Combustion and smoke on Tuesday.

Educate me! Happy Saint Patrick's Day

EBEBRATT-Ed

Probably some residual soot could be messing with the readings. It may calm down when you go back

HydronicMike

Is the OF draft .03 negative? Should be slightly positive. What was it at the breech?
High stack could also be from high draft.

When you go back I’d put the head position back to where it was and recheck combustion.
Also CO numbers at light off, at steady state-rising, falling, stable, and at shut down.

EdTheHeaterMan

I asked that question here about 30 years ago.

https://forum.heatinghelp.com/discussion/74527/yellow-smoke-spot

I think the answer is still the same:

TOO MUCH AIR. Your flame is too lean. the residual soot that was not vacuumed out completely is making you have a #2 or higher smoke test from an otherwise clean flame. After a week, go back and reduce the air mixture. (probably from the #2 setting back to #1 setting) and see if you get a zero smoke with no yellow spot. That yellow spot is unburned oil vapor that is getting blown out by the excess air

SuperTech

I agree that it is yellow from too much air. On that particular boiler with a Riello burner I am usually able to obtain a true zero smoke in the range of 12.5-13.5% CO2. Make sure to set the draft so it's slightly positive over fire, +.01-.03".