Carlin G3B Combustion Problem

Long Beach Ed

We're looking at a Dunkirk 160,000 BTU oil boiler outfitted with a Carlin G3B burner twelve years ago. The installation then was a breeze, and with somewhere around 9% CO2, 0 CO and 475 stack temp.

Back there to clean the gun 12 years later and find 1200+ppm CO. We open the air shutter until it goes down to 20ppm only to find the CO2 at 6%. Close the air shutter a hair and the CO soars back up. Close it more regardless of the CO and the CO2 doesn't budge from 6%.

Checked the gas pressure on the outlet; 3.5" wc. Clocked the meter, 160,000 as should be.

Wet base 37 year old boiler with no chamber could be sucking air from somewhere? But where? It was fine a decade ago.

Where can we start?

EBEBRATT-Ed

Pull the burner out and check the end of the burner

Long Beach Ed

I brushed it down from inside the tube and brushed down the end but I didn't look at the outside. Glanced around the firebox. Will take a better look tomorrow. Thanks, Ed.

EBEBRATT-Ed

some parts for that burner are no longer available

Long Beach Ed

EBEBRATT-Ed said:

some parts for that burner are no longer available

Probably the one I find out I need.

Long Beach Ed

Pulled the gun. The firebox is clean. Insulation up tight against the front. Front of gun pretty much flush with inside of door. Screen on the gun is clean. Checked again, 40ppm CO; 6% CO2. Try cutting the air and the CO soars. CO2 remains the same no matter what.

Meter clocks at 160,000. Orifice correct. 3.5" wc out. This once worked like a dream... This isn't good.

EdTheHeaterMan

I wonder how it might work with a ceramic fiber target wall and a blanket on the floor? That boiler was designed to have that chamber in place with the old oil burner. Just a thought. As far as the low CO2, could you be getting dilution air from a bad seal on the breach, vent connector, or any of the other section seals?

Last but not least. Is the test equipment calibrated properly? Double check it against a "known good" combustion analyzer.

EBEBRATT-Ed

What is the boiler water temp? Firing into a cold boiler will increase CO especially with no chamber.

Maybe Carlin will have an idea

Long Beach Ed

The section seals could be gone. It's a radiator-type 1975 boiler. I don't want to start playing with the firebox because it worked fine set up exactly this way 11 years ago. All that could have changed would be air leaks, I suppose. We ran the boiler well into creating steam but nothing changed. Even got new fluid for my old Fyrite wet gauge and it came up the same. Thanks for the ideas, gentlemen. This one's got me stumped. Let me know, please if you think of anything else. As a last resort, I'll reach out to Carlin, but I feel stupid.

EBEBRATT-Ed

Maybe take the jacket off and see if you have air leaks between the sections. 37 year old boiler the rope between the sections could be compromised

Big Ed_4

A few burner field techs that I talk to , whisper to pull the target chamber .

Funny how some converion burner jobs work great and some don't.

It's time to change the fluid if the reading goes up after another flip .

Long Beach Ed

The chamber's out of there. Been out since the conversion, Ed. Worked great when set up. And I put new fluid in that silly thing, tested it two, then four. Blew in it and tested my breath twice, double... all that stuff. It's just saying "no more"!

Long Beach Ed

Any new thoughts on this? Still trying...

Mad Dog_2

Maybe Captain CO Jim Davis will see this.  Maf Dog

Long Beach Ed

Still working on this one. Anyone have any thoughts?

Big Ed_4

I set them up with O2 not sure how to convert fromCO2 . The EZ sweet spot is between 4-5 O2 if the CO reading allows . What percentage are you firing at ?

EBEBRATT-Ed

Co2 or O2 whatever you use does not matter. You can use either one. Most measure O2 with the modern analyzers and convert to Co2 automatically.

Big Ed_4

What percentage is it firing from max ?

captainco

O2 on gas power burners should be 4% to 6% or CO2 8% to 10%. Usually air leaks do not cause high CO just high O2 and low temperatures. The flue temperature might help. Is there a draft reading? Underfiring certain burners creates poor mixing but this sounds like it is in a range that should be acceptable. Not sure if there is anything in the airtube that can warp or be out of position? However that don't explain the drop in CO2. Need temperature and draft.

rick in Alaska

I the burner fan dirty?
Rick

EdTheHeaterMan

I am just spitballing here. When the burner was new you were able to get 9% CO2 and 0PPM CO at 475° stack temperature. The fan was new, and clean, the air gate adjustment was new and clean, the mixing plate at the end of the burner was new and clean. If the fan has 12 years of household dust build up and the air adjustment has some dust on it I'm sure the static pressure of the dirty fan and air adjustment is different from the day it was new. How well did you clean the burner on the last maintenance? did you actually brush all the dirt off of the fan blades individually? Are all the air handling parts as clean as new? Sometimes it is the simple things that are overlooked. You may need to look closer at the burner parts.

Mr. Ed

captainco

If it were the fan the CO2 would have gone up as the O2 went down.

EdTheHeaterMan

captainco said:

If it were the fan the CO2 would have gone up as the O2 went down.

Agree ... BUT...

One might adjust the air gate to compensate as each year of build up is added to the fan blades. Eventually the static pressure is effected and you can't open the air adjustment any more. Now we need to find out why.

As I said... Just spitballing...

I was taught to brush the fan blades on every tune up in order for the fan to be able to function as efficiently as possible. I have also worked on burners that were "TUNED UP" for years by technicians that were not taught this method. After cleaning a rather large pile of dust and lint off a burner fan, I was able to close the air adjustment by 50% and get a cleaner fire than when I arrived. Static pressure did a better job of mixing fuel and air. Of course I was taught this on oil burners, but the same amount of lint can clog up a fan on a gas burner.

Just suggesting that someone look.

Mr. Ed

Long Beach Ed

Ed, we pulled the motor, really cleaned the fan, tube and screen at the end of the tube. This baby's clean.

Long Beach Ed

Just noticed I never followed up with a cause to this problem. Further testing found Excess Air to be in the 90% range. Stripped much of the jacket and resealed the clean out plates with furnace cement. That's how this boiler is sealed. Brushed and vacuumed.

Now it's running with 9.5% CO2, O2 of 4.6% Excess air of 28%, CO at 35ppm. Net stack temp is 491 degrees. That's called the 79% efficiency range. The boiler is a 50 year old Dunkirk with a Carlin G3B gas conversion burner.

Tim McElwain

Excessive air will do it every time!