SOOT.....

FXProglJr

I have 2 houses with old (1950's) American Standard furnaces and about 10 years ago we had the burners replaced with new BECKETT NX burners. Both operated fine

But about 3 years ago the fireproof lining of the firebox at one house started falling apart so my oil service company put in a new firebox. The original firebox was approx 15" round. It seems the first one they brought was too small, so the tech went out and came back with a different larger one. ( the first one was smaller than the original one and the second one was bigger). It seems the extra soot started around this time.

The tech told me he put in a slightly larger nozzle because the firebox was bigger, but assured me that it was ok. I asked the tech if the flame was ok and he said "yes, it's perfect....look, it goes all the way to the end of the firebox"

Well, since then, that furnace seems to be producing a lot more soot (in the furnace itself and in the chimney) than it used to produce or than the other one does. I called my oil service people who sent a tech back who cleaned the soot (again), told me the flame was ok and I have a problem with my chimney.

Well, except for some soot on the walls, my chimney looks ok (I sent a camera down to take a look) and I've always thought soot was produced by improper combustion. But I must say that the flame is the same color as it always was and is the same color as the furnace that's ok.

Where should I start looking for the problem? If you need any more info, photos, videos, just let me know

Any help is appreciated

Frank

STEVEusaPA

What are the combustion readings? Proper draft, true zero smoke, excess air, CO, etc.
Sounds like the burner isn't set up correctly. Could be nozzle, pump pressure, combustion air, any or all in combination.
Anyone who's calling a flame good by eye with an NX burner is a hack, sorry.
And what 'problem' does the second guy say, you actually have with the chimney?
Too rich or too lean, can look the same until it really gets out of whack.
The soot on the walls may be dirty and/or leaky ductwork, or cracked heat exchanger.

On a side note, why you putting NX's in 70 year old furnaces, and of course, why are you still using 70 year old furnaces?

FXProglJr

well….thanks for the response….guess you’ve figured out I don’t know much about burners – that’s why I’m here. To answer your questions/comments:
What are the combustion readings?. Proper draft, true zero smoke, excess air, CO, etc. – sorry, I know they took some readings when they first installed the new burners, but don’t remember what they were nor did I keep a record. I’ll have to do that in the future.

Sounds like the burner isn't set up correctly. Could be nozzle, pump pressure, combustion air, any or all in combination. Again…this is why I’m here. Suggestions?

Anyone who's calling a flame good by eye with an NX burner is a hack, sorry. Ok….I’ll keep that in mind and insist on them bringing test equipment from now on.

And what 'problem' does the second guy say, you actually have with the chimney? not good enough draft….they suggested I keep a window in the basement partially open to help. But I did check the chimney......other than some soot on the walls, it's clear and there is a draft.

Too rich or too lean, can look the same until it really gets out of whack.
The soot on the walls may be dirty and/or leaky ductwork, or cracked heat exchanger. – the soot is on the sides of the chimney clay liner and inside the furnace by the heat exchangers above the firebox

On a side note, why you putting NX's in 70 year old furnaces, - because when I started having trouble with the old burners and stack repays, this is what my burner/delivery company suggested.
and of course, why are you still using 70 year old furnaces? well…..over the years I’ve asked several technicians if it was time to replace these furnaces…….every one of them told me “no….what you have here is a tank….no need to replace it until it fails completely”

Steamhead

Are these "furnaces" as in hot-air heat, or "boilers" as in steam or hot-water heat?

What make and model are they?

I like the NX, but it produces a lot of static air pressure by design, so putting it in a unit that has little back-pressure thru its heat exchanger can lead to loss of retention. I had that happen years ago with an AFG that someone else had installed in an old American-Standard A-505 steamer. Switching the chassis to the AF solved the problem.

FXProglJr

Thanks for any help you can provide. These are American Standard boilers for steam heating in 2 family houses. I've attached photos of the furnace and the nameplate (although it's not easy to read)
Frank

STEVEusaPA

These are boilers, not furnaces.

EdTheHeaterMan

Your soot problem is from improper burner adjustment. Also, you mentioned the nozzle size was increased to match the chamber. Was the heat in the building adequate when the smaller size nozzle was used? Have you noticed a reduction in the amount of oil used per season?

With something that old you can keep it operational and also minimize your oil consumption with several adjustments. One is that your boiler probably has no baffles in the heat exchanger area. I have used fire brick strategically placed inside the cleanout doors to slow the flow of combustion gasses thru the boiler. There were manufacturer's baffles made specifically for that boiler, I'm sure they are long gone and you won't easily find them anywhere so just use fire bricks cut to fit.

Also, the firing rate can be maximized to cycle the burner at just the right amount. Too much fuel will cause short cycling... Too little will take too long to make steam. So make note of the amount of time each cycle is during the season, and what the outdoor temperature is that corresponds to the cycle times.

The next time the burner is serviced ask what the nozzle size is removed and what nozzle size the replacement nozzle is. Also, make sure they adjust for a ZERO smoke See if the different size is giving you a better cycling rate. and if the annual fuel usage is lower.

Ideal cycles on the pressure limit is longer than 7 minutes. If you are cycling at 5 minutes or less you are probably over fired.

This would have been checked by me when I installed the new burners. But that is just me. I want to start steaming within the first 15 minutes on an old boiler like that, then have Cycles no shorter than 7 minutes burner operation once the pressure limit was reached. The ideal would be over 10 minutes of burner operation between off by the pressure limit

EBEBRATT-Ed

@FXProglJr

the bottom line is you need a technician who know the NX burner, and has the proper testing equipment.

You don't have one now