Combustion: Can't get even a trace of smoke

seized123

I just fired up my old boiler (22 year old Weil-McLain WGO-3, Beckett AFG with F3 head, probably a .75 70B nozzle which is a little smaller than spec) after making much needed improvements (2-pipe to 1-pipe but with Tigerloop and generally getting the supply line up to code, new A2VA-7116B pump, totally new flue duct configuration, new combustion chamber liner, a cleaning - lots of soot - various other changes), and checked it out with my Bacharach wet kit, numbers below.

When measuring smoke with this old smoke tester pump you are supposed to adjust the air shutter so you get just a trace, then open the air just enough to get zero, but I got zero smoke on all possible air settings, 1-10. I guess no smoke seems good on the face of it, but I found it strange that I couldn't get even a trace, and it's a little disconcerting because a trace setting would give you a landmark so you know you're not giving too much air when you open it up just a little to get zero. The CO2 however with the Fyrite tester seems good, so I figure I should be okay?

Pump pressure: 140 psi
Flue temp: 370-430 F
Draft: -0.035/ -0.01to -0.02
Air shutter setting: 2 6 7 8
Smoke: 0 0 0 0
CO2: 12.5 at 6; 12.0 at 7; 11.0 at 8

I left the setting at 7. I will still have a pro come in and use his digital analyzer and hopefully determine the best nozzle size, etc., but I have not had good experiences with "tuneups" lately and would like to know as much as I can in advance.

Steamhead

Not bad!

EBEBRATT-Ed

Never seen a burner that wouldn't make smoke. The numbers you show are the air band. What about the air shutter is it open somewhat? It would only have to be cracked open to make the air band adjustment not make much difference.

MaxMercy

I would think you would be making at least some smoke at CO2 of 12.5%, other than that, those numbers look great.

Are you using the right paper media and pulling 10 strokes? Also, check to see that the rubber tube isn't ripped and of course make sure you test before the barometric damper.

EdTheHeaterMan

Dont worry about it @seized123. You may have a nozzle size that is the smallest acceptable firing rate for that burner setup.

I remember teaching adult evening education class on oil burners at the local tech school. (long time ago). I had a live fire furnace in the class room that we operated with a single wall vent pipe sticking out the window. It was a Singer upflow model with a Beckett AF burner. I wanted to illustrate some ignition problems and some smoke problems with that burner. It was so stupid proof that even with the wacky adjustments, the darn thing would not fail. I was convicence that that Beckett burner was the most stupid proof burner in the market.

So turning the air gate and air band to the most closed position may not get you a smokey fire. And the 12% CO2 is a good thing. And since you are going to get a pro out there for a final adjustment before you get into the heating season, you should be ok to run it for a few hours before they get there.

You may also have a problematic smoke tester.

seized123

Yes, the smoke tester might have a problem, though last time I used it in May I got trace smoke until I opened the shutter some more. I’ll look more closely at it.

I wish there was an adult ed oil class around here. There was one the next county up but they discontinued it recently.

EdTheHeaterMan

seized123 said:

Yes, the smoke tester might have a problem, though last time I used it in May I got trace smoke until I opened the shutter some more. I’ll look more closely at it.

I wish there was an adult ed oil class around here. There was one the next county up but they discontinued it recently.

Good thing. You would drive that instructor crazy

Steamhead

The other thing you might try is a "Low Firing Rate Baffle", Beckett part# 5880. It partially restricts the air coming off the fan so the band and shutter have more range of adjustment. They're not expensive, here is one source:

https://www.supplyhouse.com/Beckett-5880-Low-Fire-Rate-Baffle-for-AFG?utm_source=google_ad&utm_medium=shopping_neutral&utm_campaign=Shopping_Neutral_New_users&gclid=Cj0KCQjw9rSoBhCiARIsAFOipllp4F5LxbVjkqF03BxT_1aiVZie0ONSDvLpUbEx-PjhRdM-TNiqkYkaAkdeEALw_wcB

EBEBRATT-Ed

I had a job once (40 years ago) that we had installed a Beckett AF in a customer's old HB Smith model 24 boiler, and they ran it for 2 years until the boiler failed.

We installed a Weil #66 (you could purchase just the boiler less burner) and used the Beckett over in the new boiler. The firing rate was around 2gph if I remember right.

We started it up without making any burner adjustments and got 13% Co2 with no smoke. I couldn't believe it. So, we tested it a couple of times and even tried a different smoke tester. This was long before electronic combustion testers. Fyrite fluid may read low when it goes bad, but it will never read high. We added a tiny bit of air to drop the Co2 a little to give it some margin for error and the thing ran like a champ.

jesmed1

Steamhead said:

The other thing you might try is a "Low Firing Rate Baffle", Beckett part# 5880. It partially restricts the air coming off the fan so the band and shutter have more range of adjustment.

I just looked into downfiring my Weil-McLain oil boiler to a 0.75 gph nozzle using an F3 head in a Beckett AFG, same setup as you have. My recollection is that the Beckett AFG manual says that an F3 head firing below 0.85 gph requires that low firing rate baffle. At 140 psi, you'll be right on the ragged edge of 0.85 gph. So you may need that baffle.

Steamhead

EBEBRATT-Ed said:

I had a job once (40 years ago) that we had installed a Beckett AF in a customer's old HB Smith model 24 boiler, and they ran it for 2 years until the boiler failed.

We installed a Weil #66 (you could purchase just the boiler less burner) and used the Beckett over in the new boiler. The firing rate was around 2gph if I remember right.

We started it up without making any burner adjustments and got 13% Co2 with no smoke. I couldn't believe it. So, we tested it a couple of times and even tried a different smoke tester. This was long before electronic combustion testers. Fyrite fluid may read low when it goes bad, but it will never read high. We added a tiny bit of air to drop the Co2 a little to give it some margin for error and the thing ran like a champ.

The AF would run fine in a 66, but not in a 68 or Gold. For those you need the AFG with its higher static pressure.

HVACNUT

You made all the air adjustments with the shutter. What's the band set to? It shouldn't be blank with an F3 head. 
If the band was closed, and the shutter was at a 1, firing .89 GPH with an F3 head, the paper should've been black.
I wouldn't think you'd need the LFB at that rate with the F3 head.

EdTheHeaterMan

I know how to test your smoke sample pump. Get yourself a 4.00 GPH nozzle and run your burner with that. if you don't get a #10 smoke by the second pull, then your smoke tester is not working.

Don't actually do this because this message has been brought to you by:

Click on Spoiler

MikeAmann

He already has an AFG, so I assume that the LFB is already there.
My guess is that he needs to reduce the air by closing down the shutter or band - the one that he didn't touch.

I have a Beckett AF on my HWH. .65x70B nozzle at 100 psi.
It is common for your air band to be nearly closed, like this:

When you get in range, then only a small adjustment of the air shutter will take you from no smoke to black soot, like this: (look at 4 and 5)

MaxMercy

MikeAmann said:

He already has an AFG, so I assume that the LFB is already there.
My guess is that he needs to reduce the air by closing down the shutter or band - the one that he didn't touch.

What's odd though is that he's a 12.5% CO2 - he's right at the edge of smoke. Honestly, if I could get 12.5% CO2 and no smoke, I would leave it as is!

STEVEusaPA

You could check the ohms while adjusting the air band and shutter. But I'd still leave it to an actual pro, or work with a pro properly trained in combustion.

Steamhead

MikeAmann said:

He already has an AFG, so I assume that the LFB is already there.

Not always.

Bob Harper

If you use a smoke test pump on a cigarette, it will show some residue. That's a quick bump test. You really need a pro certified in combustion analysis. A digital meter will show you the CO, O2 and calculate the CO2 unless it's a UEI which measures CO2 and calculates the others. Adjusting to CO2 is a bit old school versus looking at the delta T, O2 and CO which is why I advise use someone who took the NCI course. It all ties together.

seized123

Thanks @Bob Harper I assume this photo below means the smoke test pump works, which I thought it did because it worked last time I used it and could get a trace. Weird color but that’s because I burned a piece of cardboard to get it.

Pro from oil company will supposedly come tomorrow. Even with a digital combustion analyzer, he would be expected to do a smoke pump test too, right? 

Also trying to learn what the suggested LFB does. Also FWIW below is a picture of the firing head or whatever it’s called.

seized123

HVACNUT

seized123 said:

Yup, that's an F3 head. 
Can you post a pic of the air settings?

seized123

Yup @HVACNUT:

seized123

Also, don’t know if it makes a difference but it has a new draft control damper and no matter where I moved the adjustment knob the flue draft stayed constant at about - .035.

I recently switched from a 7” damper to 8” because interestingly (to me) Field Controls says that with 7” flue piping like I have you need to use an 8” damper (so you need to use a reducer).

(@HVACNUT see requested photos in last post.)

jesmed1

Here's the low fire baffle.







The baffle clips onto the partition under the igniter. I don't know the why's of the design, but you can see it impedes airflow on either side and admits air through the center cutout.

jesmed1

seized123 said:

I recently switched from a 7” damper to 8” because interestingly (to me) Field Controls says that with 7” flue piping like I have you need to use an 8” damper (so you need to use a reducer).

That seems odd. We have Weil McLain WGO-5's which are basically the same boiler as yours but larger, and we have a 7" flue with a 7" damper (no reducer) and it works fine.

Steamhead

seized123 said:

........Also trying to learn what the suggested LFB does.........

Here's a short summary from Beckett:

https://www.beckettcorp.com/bulletins/understanding-the-low-firing-rate-baffle/

Ignore the part about the inlet air shutoff. That was a good idea that just didn't work well, and is no longer used.

EBEBRATT-Ed

The baffle increases the air velocity to create good combustion at lower firing rates. Which is why I always preferred Carlin's adjustable head + the head removes for cleaning.

But Becketts are a good dependable burner with combustion that is as good as any burner.

seized123

Okay, LFB: right off the bat I can guess if the air bands (those bigger windows?) are closed and I’m getting no smoke on all shutter settings then I can put in the LFB (I might get smoke then, right?) and open the air bands some and then fine tune using the air shutters?

According to a standard nozzle chart I saw the .75 gph nozzle run at 140 psi should be just under .90 gph. Indeed, the sticker on my WM WGO-3 says .95 gph, so that would be underfiring it some. The chart in the Beckett article (thanks @Steamhead) says no baffle for .90 gph, but yes baffle for .85, so it’s a fine line. But it seems like it’ might be a good idea.

BTW, I’m a little worried about possible impingement. I only ran the thing a couple minutes and looked at the back wall of the new combustion liner and it was a little gray-black, and when it’s running I can’t tell if the flame is licking the back wall. Would an LFB increasing pressure increase chance of impingement? Is that yet another thing you have to adjust for?

Steamhead

seized123 said:

Okay, LFB: right off the bat I can guess if the air bands (those bigger windows?) are closed and I’m getting no smoke on all shutter settings then I can put in the LFB (I might get smoke then, right?) and open the air bands some and then fine tune using the air shutters?

Yes.

seized123 said:

According to a standard nozzle chart I saw the .75 gph nozzle run at 140 psi should be just under .90 gph. Indeed, the sticker on my WM WGO-3 says .95 gph, so that would be underfiring it some. The chart in the Beckett article (thanks @Steamhead) says no baffle for .90 gph, but yes baffle for .85, so it’s a fine line. But it seems like it’ might be a good idea.

The baffle is not expensive, so try it and see.

seized123 said:

BTW, I’m a little worried about possible impingement. I only ran the thing a couple minutes and looked at the back wall of the new combustion liner and it was a little gray-black, and when it’s running I can’t tell if the flame is licking the back wall. Would an LFB increasing pressure increase chance of impingement? Is that yet another thing you have to adjust for?

The flame might be a bit wider but should not be longer. Final determination will be the combustion test.

seized123

I hope the pro coming tomorrow has one. If he postpones I’ll order one.

EdTheHeaterMan

Once you have it set up by a Pro, DO NOT install the LFB after he leaves. That part will change the settings and air flow and VOID the adjustments the Pro made.

EdTheHeaterMan

@seized123, When you get this finished, Weil McLain might hire you for Tech Support on their WGO boiler line. You have asked more questions in the past 2 years that I have heard in my 40+ years of doing this work. Hope you have absorbed everything. You should be able to answer queries from others soon.

seized123

EdTheHeaterMan said:

Once you have it set up by a Pro, DO NOT install the LFB after he leaves. That part will change the settings and air flow and VOID the adjustments the Pro made.

Yup, I even thought of postponing the appointment so I can get one first, but we’ll see if he can do it without the baffle, or if they stock one.

EdTheHeaterMan said:

@seized123, When you get this finished, Weil McLain might hire you for Tech Support on their WGO boiler line. You have asked more questions in the past 2 years that I have heard in my 40+ years of doing this work. Hope you have absorbed everything. You should be able to answer queries from others soon.

I wouldn’t ask so many questions if I didn’t always get such great answers. Every time I ask I get helpful answers and often tips I never would have gotten elsewhere (example, bicycle pump to clear oil lines - sound familiar? -  which I’ve used twice now.)

This stuff is interesting. The county-run trade school one county up used to offer oil tech courses, and I would take it but they discontinued it due to not having a teacher. They do have HVAC in my county but it filled up this semester before I could register. 

Anybody in the Hudson Valley (NY) area wants to teach HVAC and/or oil heat in the evenings, especially Orange County, it’s called BOCES. The one near me is “Orange/Ulster BOCES” and I know they’re looking for an HVAC instructor.

seized123

I found this very helpful article on air and the Beckett AFG:

https://thermodynamicsboiler.com/common-service-questions-asked-about-the-afg-oil-burner/