VERY odd soot pattern in Trio combustion chamber

Ted89

Have a 4 year old Trio with a Carlin EZ conversion gas burner. Flame outs from a dirty flame sensor and an overdue servicing led to opening the chamber. Very heavy black soot, but look at the pattern in the photo of the main chamber. Soot left, NO soot right. What could have caused that pattern??

After cleaning, the tech had to change all 3 adjustments to get it back into spec. Some were off a lot. Something happened. Any quess as to some root causes to check?

Thanks

STEVEusaPA

I'd guess impingement caused by poor combustion. Bad gas valve, wrong pressure? What's the end of the burner look like? Warped end?
How was the draft?

Steamhead

Was this a universal-fit burner, or one specifically furnished for that boiler? The latter has a welded flange that matches the bolt pattern. These boilers run with a slight positive pressure over the fire, and you need the right setup for them to run well.

Ted89

I can answer some of your questions. The gas flow was over 4", the spec was 3.2 to 3.8". A change to 3.2" and more air brought the CO to spec. Assuming the value was commissioned at about 3.5", is it normal for it to produce over 4" in 4 years? Do they drift that much?

The draft will be measured today. But nothing in the 24' x 6" SS round flue setup has changed. Could an air leak on the chamber door "steer" the sooty flame sideways?

I believe the Carlin EZ is a conversion burner (universal). The tech did not comment on a warped burner end. Thanks.

Jamie Hall

That pattern of a really clean area and soot elsewhere very strongly indicates to me that you had active flame impingement on the wall in the clean area. Something was way out of whack in there.

captainco

I would assume someone had to drill the orifice for the correct size but was it correct? Good chance it was drilled crooked which is why the flame may have impinged on the left side. Gas pressure does not give us btus. We need to know the orifice size or the cubic feet of gas. I suppose if you make the flame small enough it won't impinge, but is that a fix or a bandade?

GBart

Never set up right in the first place.

This is LP or NG?

Tim McElwain

All good answers so far. I would start from scratch and go through the entire setup and installation just to make sure. Then a combustion analysis to confirm the setup.

Steamhead

I just talked to Dave Thomas, whose company (Boyertown Furnace) sells the Trio boilers to F.W. Webb. The Trio is the same as the Solaia- both are based on the Biasi block, and these boilers run very well when set up properly.

Just like oil burners, gas burners come in different configurations for different boilers. If that EZ-Gas does not have the specific welded-flange air tube and other air-handling parts for that boiler, it will not run properly. This is due to the firing zone design, which among other things, as I said, runs at a slight positive pressure. When we convert Solaias, we always get the proper burner and have never had a problem.

Dave is as good as it gets. Give him a call tomorrow at his office, 610-369-1450. He'll be able to get you what you need. You will probably end up replacing the entire burner with the proper EZ-Gas variation, and using the other one for something else that is not as critical.

Ted89

Thanks. What does "air impingement" mean? Why would it lead to NO soot at all or the right side o the back wall?

My installer had done several Trio and EZ Carlin on natural gas with no problems. My burner does, in fact, have a welded flange for the Trio which bolts to the chamber door. In an earlier post, I incorrectly said it was a "universal" burner. I also said it was a conversion burner because the installer called it that- but mine was not a conversion from oil- it was gas day 1.

According to Carlin, my burner had a label on it which identified it as having the right .189" orifice pre-drilled at the factory.

Jamie Hall

Air - or more accurately flame -- impingement; if the hottest part of the flame impinges on a surface, no soot will be deposited. Indeed, any soot present will be burned away. Soot will be deposited in areas where cooler (yellow/orange) parts of the flame are in contact with a surface.

In fire investigations, that can be a very good way to tell where the fire was actually burning...

One can get a somewhat similar effect -- but usually quite distinguishable -- if there is a high velocity air flow deflecting the flame and combustion products away from the surface.

Ted89

Thanks,
Can you see if the flame is impinging on the left chamber wall if the inspection port is on the right side of the front face (swing door)? It's a triple pass cast iron Trio/Biasi.

Jamie Hall

Ted89 said:

Thanks,
Can you see if the flame is impinging on the left chamber wall if the inspection port is on the right side of the front face (swing door)? It's a triple pass cast iron Trio/Biasi.

Probably not. In fact, unless you can really see all around the flame, it can be very difficult to tell if impingement is occurring. But the clean areas are a really good clue!

Manufacturers go to a good deal of trouble to design the equipment so that impingement does not occur -- if only because it is almost impossible to get decent combustion numbers or efficiency if it does. This is why only certain burners, with quite specific equipment, can be matched to certain boilers.

Tim McElwain

Many times when impingement is occuring there is an odor of a product called aldehyde. It is the result of the gas flame at say 3000 degrees up to 3400 hitting a cooler surface the metal which may be at 1500 to 2000 degrees on the surface. This will cause soot deposits along with the odor of adelhyde. Keep in mind Carbon Monoxide by itself is odorless.

EBEBRATT-Ed

@ted89, You could drop the gas pressure very slightly (say from 3.5" to 3.2" wc) readjust the burner with instruments and then run and see if the impingement stops.

their are many variables in combustion, fuel composition, fuel and air temperature, draft or furnace pressure, burner run time................the list goes on and on. If your combustion #s are good but getting impingement reducing the fire very slightly may help. If #s are bad I would suspect a burner issue.

Tim McElwain

If my calculator is correct a .189 orifice is the same as a # 12 drill size or 3/16. If so at 3.5" W.C. with btu content of gas at 1050 and specific gravity at .6 it should be firing at 110,000 BTU's unless I am missing something?????

Table 1 in the Carlin manual says 3/16 on natural gas should be 75,000 BTU's I guess compensating for the air band opening and increased pressure. The notes say "maximum burner input decreases with increasing overfire pressure. Assume a reduction in maximum burner input of approximately 5% at at.1" W.C. and 10% at .2" W.C. This has to be taken into consideration.

So at 5% it would be a reduction of 5,500 from 110,000 or 104,500. At 10% it would be 11,000 reduction from 110,000 or 99,000. If memory serves me the other posting about this job says you wanted 89,000 BTU's.