Beckett AFG Efficiency Testing + Boiler sooting issue

skybolt_1

Scenario: 4 year old Force 84 (US Boiler MPO-IQ rebranded) with a Beckett AFG, Type W .45°-0.50 nozzle. Restriction plates installed in 3rd pass passages. Using a Field Controls airboot piped directly outside. No blockages in the fresh air intake.
Boiler started exhibiting sooting issues last March, combined with faint fuel oil smell. Had techs out, they replaced the nozzle stating it had probably clogged up due to lack of use over summer. Sooting issue continued. Had the chimney liner swept, there was a pretty good amount of soot cleaned out.
I purchased a Bacharach smoke tester, adjusted the airboot to trace of smoke while waiting for a rental Testo 330 to be shipped. Airboot was originally set to 5°, it has ultimately been opened up to 25°, which resulted in the following results from the Testo:

• 405.3 F = Temp Stack
  
• 4.9% = Oxygen
  
• 67 ppm = CO
  
• 12.02% = CO2
  
• 110 PPM = NOx
  
• 5.0% = NO2 addition
  
• 105 PPM = NO
  
• 85.4% = Efficiency gross
  
• 30.6% = Excess Air
  
• -0.020 in-H20 Draft
  

I believe that the CO2 and draft numbers are pretty good based on manufacturer manuals but would like any feedback on the rest of these, particularly the CO and NOx.

HVACNUT

If it is a rebadged MPO and has the same specs listed (yours should be rated 180 psi as noted in note 52, specs after 2013).I want under 50 ppm CO. Maybe go to 20° on the air and take another smoke test.

When installing the Fields Controls air boot, do you remove the air band or air gate from the burner?
What I'm asking is, if the air settings are correct on the burner, then the air boot could be 100% open because it's only going to pull what the air shutter and gate allow through. 

skybolt_1

The burner has a A2EA-6527 rated from 100-150 PSI and there is a factory sticker on the side of the burner housing that states "Pump Pressure set at 150 PSI". Not sure why that chart shows a 180 max unless it is just the max rating available?
Yes, when the boot was installed the instructions stated to remove the air band entirely, in fact I am 90% sure that you can't physically install it if the band is in place.
I just did another series of tests.
At 5 minutes run time, 25° on boot

• 388.3 F = Temp Stack
  
• 4.8% = Oxygen
  
• 58 ppm = CO
  
• 12.09% = CO2
  
• 110 PPM = NOx
  
• 106 PPM = NO
  
• 85.9% = Efficiency gross
  
• 29.8% = Excess Air
  

At 8 minutes run time, 15° on boot

• 395.1 F = Temp Stack
  
• 3.9% = Oxygen
  
• 71 ppm = CO
  
• 12.77% = CO2
  
• 124 PPM = NOx
  
• 118 PPM = NO
  
• 86.1% = Efficiency gross
  
• 22.9% = Excess Air
  

At 9 minutes run time, 20° on boot

• 403.2 F = Temp Stack
  
• 4.3% = Oxygen
  
• 73 ppm = CO
  
• 12.47% = CO2
  
• 122 PPM = NOx
  
• 116 PPM = NO
  
• 85.7% = Efficiency gross
  
• 25.9% = Excess Air
  

At 11 minutes run time, 30° on boot

• 425.3 F = Temp Stack
  
• 5.6% = Oxygen
  
• 72 ppm = CO
  
• 11.49% = CO2
  
• 107 PPM = NOx
  
• 102 PPM = NO
  
• 84.5% = Efficiency gross
  
• 36.6% = Excess Air
  

At 12 minutes run time, 25° on boot

• 429.3 F = Temp Stack
  
• 5.5% = Oxygen
  
• 74 ppm = CO
  
• 11.57% = CO2
  
• 109 PPM = NOx
  
• 104 PPM = NO
  
• 84.5% = Efficiency gross
  
• 35.7% = Excess Air
  

EBEBRATT-Ed

@skybolt_1

Your #s look good. What I have found and some recommend is to adjust for a trace of smoke and run the combustion test. Then open the air bad/shutter to lower your Co2 1%

This gives the burner a little cushion to work with. A very slight loss in efficiency which you lose anyhow if the boiler soots.

I would also check the burner head if you have not done that but with your #s doubt thats a problem.

STEVEusaPA

I don’t think the manual allows a direct vent on an MPO with an AFG. I also think your draft is too high. What’s your overfire draft.

skybolt_1

STEVEusaPA said:

I don’t think the manual allows a direct vent on an MPO with an AFG. I also think your draft is too high. What’s your overfire draft.

It's not direct vented, it's an outside air intake, and it is approved in the install manual.
Overfire draft is -0.008 in-H20.

Edit: Thanks to HVACNUT, EBEBRATT-Ed and MikeAmann. I have checked the burner head and it looks ok, no sooting or damage.

skybolt_1

I have a really strange update that has me absolutely confused, hoping that someone here has some ideas.

I went through the entire month of November and 3 weeks into December without any problems, all the way up until 12/21, this past Wednesday. Around mid-day, I got an oil delivery, around 121 gallons.

Thursday morning around 5:30 AM, I wake up to what sounds like a bass thump, but irregular. Head down to the basement and discover that the burner is pulsating like crazy, 15-20 pulses per minute. I check the air boot, it is still set at 25° where I set it back at the beginning of November. Fiddle with the air boot and am able to get the pulsing to stop around 12°-15°. But now my smoke test is hovering between a 3 and 4 on the Bacharach filter paper, where it was a nice clean trace-of-smoke before.

I pulled the tank filter, thinking that maybe the delivery stirred up a bunch of gunk; nothing, it looks almost brand new. The 10 micron spin-on filter on the TigerLoop was replaced in March, as well as the pump screen, so I haven't pulled those yet, but it's hard for me to imagine how they could be clogged if the tank filter is clean.

I pulled the blower motor to make sure that the plastic coupler connecting the motor to the pump wasn't stripped; again, it looks brand new. Pump turns smoothly.

I'm at a loss. Could it be that I got a bad batch of oil? Maybe they filled the tank with #1 or something? Any thoughts or suggestions are welcome.

SuperTech

I would definitely check the spin on filter and pump strainer. Check oil flow to the pump. Check amperage on the burner motor and test the burner motor capacitor. Make sure its not sooted up. Check oil pump pressure. 

HVACNUT

Something like this will help know if it's an oil issue. 

skybolt_1

@SuperTech, I replaced the spin on filter and checked the pump strainer (clean). Oil flow to the pump seems strong, good flow from bleeder when opened, no foaming or anything. Motor is drawing 1.29 amps during valve-on delay, 1.34 amps on run. Motor capacitor has an ESR of .09 which is way under the curve for a 16uF 240v capacitor.
Checked the passages, some soot, maybe 1/64"? Vacuumed it out.
Don't have a pressure gauge for the pump but will get one.
Pulsation problem continues after all of the above.
@HVACNUT what's going on in that picture? Vacuum gauge on the tigerloop feed line?

SuperTech

That's a vacuum gauge on the tiger loop so the vacuum on the suction line can be monitored. Are you able to check vacuum on your oil pump as well as checking pump pressure to the nozzle? Can you check draft over fire and in the breach? Combustion analysis?

skybolt_1

@SuperTech I'll order the vacuum gauge now. I have already ordered a 200 PSI pressure gauge to check the nozzle pressure, won't be here until next week.
Most recent combustion analysis from early November were:

429.3 F = Temp Stack
5.5% = Oxygen
74 ppm = CO
11.57% = CO2
109 PPM = NOx
104 PPM = NO
84.5% = Efficiency gross
35.7% = Excess Air
-0.020 in-H20 Draft

I rented the combustion analyzer so I am not able to recheck at this time.

skybolt_1

@SuperTech, I got both the vacuum gauge and the pressure gauge. Vacuum gauge, installed on the pump suction line, reads 0 when the burner is running (which I understand to be the desired value). Pump pressure to the nozzle is 150 PSI, same as the factory setting sticker on the side of the burner indicates.

SuperTech

Everything looks good except for the 74 PPM CO, I'd prefer to see that lower, definitely below 50 PPM. That draft measurement, was that taken over fire or in the stack? 

skybolt_1

That was taken in the stack. I don't have the specific measurement of the draft over the fire but it was very close to zero. The instructions provided with the boiler state to target a draft of "zero inches water column in the canopy" which is accessed by removing a threaded plug in the back of the boiler near the flue. I made measurements over the fire, in the canopy, and in the flue. I could never get an actual "zero" reading but it was very, very close.

irishrosepotter

I am having the same issue with my Burnham MPO-IQ Boiler with a Beckett AFG, it keeps creating soot. Had a new tech work on it today for 8 hours, cleaned it reset everything back to manufacturers spec and it still is creating soot. He is at a loss as to why. Original installer is at a loss. Unit was installed Jan 2022. I have been without heat for 6 weeks now.

skybolt_1

irishrosepotter said:

I am having the same issue with my Burnham MPO-IQ Boiler with a Beckett AFG, it keeps creating soot. Had a new tech work on it today for 8 hours, cleaned it reset everything back to manufacturers spec and it still is creating soot. He is at a loss as to why. Original installer is at a loss. Unit was installed Jan 2022. I have been without heat for 6 weeks now.

That is a REALLY bad situation. Sorry to hear that. My boiler is exactly the same as the MPO-IQ, but was rebadged for Ferguson (plumbing supplier) as a "FORCE" boiler. But it was built by US Boiler and is the same unit, slightly different housing.

EdTheHeaterMan

I have solved several AFG burner problems with a Riello in the past.

Just sayin'

skybolt_1

Not that I'm doubting you, but it seems crazy that switching out the burner for a Riello would be necessary on basically brand new units!

EdTheHeaterMan

Stranger things have happened. Some locations and configurations just are unfriendly. Can't say why. Case on point... READ THIS
https://forum.heatinghelp.com/discussion/comment/1689835#Comment_1689835

To get the answer to that particular problem might have taken thousands of dollars of forensic testing to find out that replacing the equipment would be the best fix. Or you can bite the bullet and just make the change.

There was another story that was fixed by a Riello burner because of the way the primary control was powered by the “BACK EMF” of the motor The combustion issues with the standard R8184G primary were corrected by replacing it with an electronic Carlin 70200. But the electronic control was causing a different failure as a result of the quality of power from the grid to the home. The Rellio was not affected by the power quality issue because the electric motor was the generator for the electronics in the primary control/ignition module.

Why is the AFG causing a problem on two different Burnham MPO boilers? If it were my customer, I really don't care as long as there is a fix. If the Fix is a different burner and the factory will approve it, and cover some of the cost… then why bother with the forensics, Just do the fix.

Insanity is trying the same thing over and over and expecting a different result. Stop the insanity and try something new!

skybolt_1

Update: I got my hands on a Testo 300 and am doing some more checks. Here are the numbers that I just pulled after letting it run for 5 minutes:
Over Fire: -0.0200 in-H20 (fluctuates by about 0.005 +- while running)
Canopy / Breech: -0.0249 in-H20 (with adjustment weight all the way out at the 2 mark)
As a test, I pulled the barometric controller completely off, leaving the hole entirely open. Canopy / Breech draft went to -0.0136 in-H20.
Per the manual for this unit, "Adjust draft regulator for a draft of zero inches water gauge in the canopy after boiler has been run five minutes." However, it also states that "A negative pressure reading up to -.03 inches water column is acceptable for proper operation."
Is the draft here too high?

EBEBRATT-Ed

@EdTheHeaterMan

Sounds like another "Blu Ray". Where is John Cameron Swazy?? They use blue flame in Europe and the UK. It's probably the quality of the oil here that sucks.

It wouldn't be the first time something worked in the lab and won't work in the field and it will not be the last. I have seen many instance with that.

skybolt_1

EBEBRATT-Ed said:

It's probably the quality of the oil here that sucks.

This goes back to my original update... things worked great for 7 weeks after I tuned the burner in November. After I got an oil delivery on 12/21, that's when the issues started.

MikeAmann said:

The mounting of the draft regulator must be straight and level.
Try to adjust the draft regulator to achieve these numbers, or as close as you can get.

The regulator is straight and level, and the weight is fully "out" to the #2 marking. Best draft I can get is -0.0249 in the breach. This is a three pass design, with baffles installed. Not sure how much that matters, according to the manual it should be 0" over fire, 0" in the breach with baffles installed, with the caveat that "These values are minimum and could be as much as -.03" w.c., more without impacting performance. Pressures based on 11.5% CO2"

Wonder if I need a second draft regulator?

SuperTech

If anything you would want to change the position of the baffles to lower the over fire draft.

STEVEusaPA

MikeAmann said:

Over Fire: -0.0200 in-H20 GOOD
The fire itself should generate -0.0200 in-H20.
Therefore, you should read -0.0400 in-H20 in the breach, assuming no restrictions...

Over Fire for this boiler: NOT GOOD.
Breach should be 0 and OF slightly positive.

To the OP, this is a set up problem, and maybe a combustion air problem, then maybe a draft problem.
Again, Z dimension is of utmost importance.
If you think it's the oil, pull some oil and have it tested. But I think there's a combustion air problem, because maybe this burner was set up incorrectly on a 90° day.
What were the rest of the combustion numbers?
Do you have any baffles in? The nearly identical OF and breech measurements tell me you probably don't, or aren't measuring draft properly.
Here's the other things that need to be double checked.


Not to offend you or anyone who was already there, but the chances of installing two regulators correctly is pretty much 0.
If you actually found someone who understood what to do, you'd consider a neutral pressure point adjuster, which is what I had to do on my MPO. If they say 'what's that', they're the wrong tech.

EdTheHeaterMan

skybolt_1 said:

EBEBRATT-Ed said:

It's probably the quality of the oil here that sucks.

This goes back to my original update... things worked great for 7 weeks after I tuned the burner in November. After I got an oil delivery on 12/21, that's when the issues started.

MikeAmann said:

The mounting of the draft regulator must be straight and level.
Try to adjust the draft regulator to achieve these numbers, or as close as you can get.

The regulator is straight and level, and the weight is fully "out" to the #2 marking. Best draft I can get is -0.0249 in the breach. This is a three pass design, with baffles installed. Not sure how much that matters, according to the manual it should be 0" over fire, 0" in the breach with baffles installed, with the caveat that "These values are minimum and could be as much as -.03" w.c., more without impacting performance. Pressures based on 11.5% CO2"

Wonder if I need a second draft regulator?

What size is the vent connector pipe? i have noticed that some times using the 7" draft diverter on a 6" vent connector pipe will allow for a lower draft adjustment. I have also used two Barometric Draft Controls on some vert tall chimneys in order to get the draft low enough for consistent burner operation.

Since you are just on the verge of the allowable -0.03 draft, I would make the assumption that there will be times when you are not present to measure the draft, that the draft at the breach or canopy WILL be greater than that allowable number.

skybolt_1

@STEVEusaPA, interesting... here is the same page from my manual...

skybolt_1

EdTheHeaterMan said:

What size is the vent connector pipe? i have noticed that some times using the 7" draft diverter on a 6" vent connector pipe will allow for a lower draft adjustment. I have also used two Barometric Draft Controls on some vert tall chimneys in order to get the draft low enough for consistent burner operation.

Since you are just on the verge of the allowable -0.03 draft, I would make the assumption that there will be times when you are not present to measure the draft, that the draft at the breach or canopy WILL be greater than that allowable number.

6" vent, 6" draft diverter. And I suspect that at my current airboot setting of 15°, the intermittent pulses that I still occasionally get are a result of those greater than -0.03" events.

EBEBRATT-Ed

Two different spec sheets. Inadequate mfg testing.

In my opinion positive fired units and balanced pressure units are difficult to make work. They do it to get more efficiency. The efficiency gained by firing a positive pressure is almost negligible.

Designing a unit that has to be "perfect" to run in the field never works. This has been tried in the past. It does not carry over to a mass-produced piece of equipment.

Equipment that has to be perfect to run....won't run. Combustion changes constantly. draft changes with air temp, combustion air temp changes, fuel changes composition and temperature. The equipment has to be designed to run in a "safe range" not a perfect range

skybolt_1

Well, I'm throwing in the towel on this. I just started a new job and the time that I have to try and figure this out solo has gone to zero. I put in a call in to Joyce Cooling & Heating in Nashua (listed on the contractors page here) and they are sending out a tech tomorrow to take a look at this. Hopefully, they will be able to figure out what's going wrong here. I will certainly update the thread once I have some more info.

Dyingtofly

I'm fascinated by this mind boggling situation, skybolt! You stated that the boiler is 4 years old and I'm assuming operation was without issues up until March of 2023 but then you got it to operate properly in November. Then, after a fuel delivery on December 21st you woke up to the thumping sounds of a pulsating burner (often the result of excessive air). The thing that immediately jumped to the forefront in my thinking was the quality of the fuel oil (i.e. was it a higher sulfer content or poor process/quality fuel). Were you using the same delivery company, etc.?). You also were careful to note that you had the nozzle changed, the filter and screen checked or changed, and the chimney liner brushed, but how about the cast iron sections? With all of your thoroughness I can't imagine you would have neglected brushing and inspecting the sections. Did someone check the integrity of the combustion chamber (no broken material, excessive cracks, etc.)?
I went and looked at Ferguson's literature and noticed that it calls for a .60-GPH nozzle. I then went to the Delvan nozzle site and found they recommend a type "A" nozzle as opposed to a "W" because "it is especially well suited to fractional gallonage and flame retention burners". That coincided with information I found on a Beckett nozzle chart for the AFG model as well. Was there a reason for a nozzle size change or is that what actually came with the boiler & burner? As a former (now retired) HVAC service technician, I enjoy having several choices at my home; water-source heat-pump fed by my artesian well, a couple of ductless split heat-pumps, a cast iron Crown boiler converted from an AFG oil burner to a Midco LP gas burner and, my favorite, a Vermont Casting soapstone woodstove. Needless to say, I love to tinker.
Well my friend, I'm anxious to hear what the next technician finds! Looking forward to your next post... I think.

skybolt_1

@Dyingtofly, your sentiments regarding the fuel quality were exactly what I suspected since having the tank filled was the only change between November. Same delivery company I have been with for the past two years, although it was the first fill I had gotten since the early spring.
Here are pictures from December when I opened up the unit to clean it out. I saw no evidence of cracks or damage:


Regarding the nozzle, the unit shipped with a 0.50x45W, and it is also indicated in the manual (picture a few posts back), despite it being rated at .60-GPH in both the literature and by the sticker. I have no idea why this is...

jesmed1

skybolt_1 said:

Regarding the nozzle, the unit shipped with a 0.50x45W, and it is also indicated in the manual (picture a few posts back), despite it being rated at .60-GPH in both the literature and by the sticker. I have no idea why this is...

If you look at the Beckett AFG specs you posted above, the spec'd 0.50 nozzle is supposed to be run at 150 psi, which presumably results in the actual 0.60 gph input rate.

Remember that the nominal nozzle gph is based on 100 psi.

MaxMercy

skybolt_1 said:

@Dyingtofly, your sentiments regarding the fuel quality were exactly what I suspected since having the tank filled was the only change between November. Same delivery company I have been with for the past two years, although it was the first fill I had gotten since the early spring.

Questions for the group - what if this is an oil issue? How is something like this resolved short of pumping out the tank? Can a different pump pressure/nozzle angle/z dimension change etc. solve this? An additive maybe???

skybolt_1

Update: the tech from Joyce Cooling & Heating came out this morning. Completely stumped. We talked through everything that's happened, he witnessed the pulsation, made some adjustments to the air to get the combustion numbers a bit better. He was able to get the following numbers at 20° on the air shutter:

• 
  
• 379.5 F = Temp Stack
  
• 4.3% = Oxygen
  
• 7 ppm = CO
  
• 12.47% = CO2
  
• 84.7% = Efficiency gross
  
• 25.9% = Excess Air
  
• -0.029 in-H20 Draft
  

Even with these numbers, I've noticed an occasional pulse.
He also pulled a 2000 Ohm reading on the cad cell, which he said was pretty high, but he didn't believe it warranted replacement.
Nice guy, didn't charge me, said he would raise the case at his service meeting tomorrow morning to see if anyone else has ideas.

MaxMercy

skybolt_1 said:

He also pulled a 2000 Ohm reading on the cad cell, which he said was pretty high, but he didn't believe it warranted replacement.

2000 ohms?? Is that while firing or maybe 2000 0hms in ambient room light?

Most controllers I've run across shut down at 2Kohms or even less - I've seen them intermittently lockout at 1600 ohms. It wouldn't be 200 because that is excellent/low. My AFG runs about 225 ohms and that's downfired to the minimum fire rate Slant recommends for my boiler.

Do you know if your AFG has the low firing rate baffle installed?

skybolt_1

I must have misread it over his shoulder. Bet I missed a decimal. It was probably more like 200-210 then. He said he usually sees them in the 125-150 range.

Yes, I have the baffles installed (note: picture was taken before cleaning).

MaxMercy

skybolt_1 said:

I must have misread it over his shoulder. Bet I missed a decimal. It was probably more like 200-210 then. He said he usually sees them in the 125-150 range.

200 would be extraordinarily low (excellent). I haven't seen anything in 125 ohms range on such a low fire rate, but if the tech wasn't concerned, don't worry about it.

Anyway, the baffle I was speaking of is the single low firing baffle that is in the AFG burner itself, not in the boiler. Lift up the transformer (burner off ) and it will be right where the right angle turn is of the burner tube. The baffle increases back pressure to improve combustion without changing the amount of air.

skybolt_1

Ah, thanks for the clarification! Yes, I just verified that baffle is installed on the burner.

MaxMercy

skybolt_1 said:

Ah, thanks for the clarification! Yes, I just verified that baffle is installed on the burner.

Honestly, I would try removing it and see if that helps the instability.

skybolt_1

OK, I can certainly try that. Unfortunately I am without an analyzer, and it is a warm day today. So I will probably need to do this later on.

I suppose a more general question is whether, given the numbers I've seen to date, I can make adjustments to the airboot, use a combination of smoke test+stack temp, and be reasonably confident that the changes I'm making to increase combustion air aren't having a significant impact in other areas? Probably a pipe dream but figured I'd ask.