what caused this boiler to soot up

Joseph_4

Had a customer last year whose boiler completely sooted up. I took it apart, power washed it, changed the chamber cleaned the chimney and set back to manufactures specs.. its a peerless wb/04-125. I made sure when i left it it had a zero smoke. used a combustion analyzer to set up. the lowest o2 possible was 6%. any higher made carbon monoxide rise to unacceptable levels/ lower o2 created smoke

over fire draft was between -.01 and -.005 at breach was between -02 and -.03

I live 45 minutes from job revisted after 3 months chamber was still pristine. Now 10 months since job completely sooted up again..

Now there was a window fan put by basement window about 15 x20 in size because customer didnt like oil smell from a leak he had.. Is that enough to have pulled flame off head and caused this?

I also see in blast tub a little build up like from after drip, but nozzle and endcone are clear of any debris. Is that any indicator why it sooted up?

Trying to figure out what went wrong
Thanks
Joe

mattmia2

Turn the fan on and see what happens to your combustion analysis and draft. Could also be system designed with sustained low return water temps causing condensation.

Jamie Hall

That fan may not have pulled the flame off the head -- that takes some doing -- but as @mattmia2 said, it's dollars to doughnuts it messed up the draught and combustion numbers. Worse, it wouldn't have to run all that long to foul the boiler (even a few hours might do it), and once it starts fouling it's not going to get any better.

EBEBRATT-Ed

-.01 over the fire is not enough draft. You have no cushion. Don't forget the perfect set up on any burner will not stay.

Changes in air density change the amount of air the burner fan delivers, cat hair, lint etc can clog the air inlet or blower wheel and fuel oil can change

I would suspect you problem is a draft issue. If the boiler is clean and the chimney is ok and doing all it can you may want to consider reducing the fire size either by pump pressure or nozzle size or a combination of both. It's better to keep the pump pressure up which gives better atomization.

And yes, the fan could be the problem. Also a little more draft will keep the smell down if they are smelling combustion gas.

When you get a burner that doesn't work at the MFG settings .....change something. Your working in the field not a lab

The MFGs have been wrong many times. Boilers in the field don't always run under ideal conditions

EdTheHeaterMan

As I followed your explanation, I was just as puzzled as you with the reason for the soot-up problem. I was also intrigued with the very close tolerance from CO to Smoke with very little adjustment room on the combustion air setting. Then I read the part about the exhaust fan. Duh... You already know the answer. YES, the exhaust fan will definitely cause the soot to start at some point. I have thoroughly cleaned a boiler that was completely plugged with the "Fluffy" soot and after proper setup to the manufacturer's settings with combustion instruments, I returned in 2 days to the same completely plugged with soot boiler.

I did not think that could happen in such a short time. especially after having a Zero-smoke reading. Then I found out they were using a "Whole House Fan" to reduce the air conditioning bill. (the boiler made DHW during warm weather). To accommodate the new energy-saving device, I added a relay that would disable the fan whenever the burner operated for DHW.

Can't run a burner and an exhaust fan at the same time. Learned that long ago at a diner in NE Philadelphia in 1979. You can't keep a pilot lit on a water heater with the powerful kitchen exhaust hoods sucking all the air out of the building. any opening becomes a make-up air inlet including chimneys. Even back then I knew enough to check the draft on a gas appliance vent. And that is because I had the Bacharach oil burner combustion kit on my service truck. That problem has several "Plumbers" scratching their heads. The trained oil heat guy needed to figure it out.

Yours truly,
Mr.Ed

Ctoilman

Definately have a solid gravity fuel flow to the burner?  

I agree having an exhaust fan in the boiler room is a definate no-no.  

I like running the WBV-04 with a 1.00 nozzle, do configure the nozzle assembly for that firing rate if its got the Beckett burner.

HVACNUT

What make and model burner?
What nozzle?
What's the pump pressure?
Is there pre purge?
How long is the flue run and what type and condition of chimney?
Typically you'll want between 4.5 and 6.5 oxygen with 25% excess air. 

STEVEusaPA

Don't forget you can add a combustion air kit (don't know which burner you have) and a blocked vent switch, wired to a Carlin ProMaxx primary, which will help with troubleshooting.

Robert O'Brien

02, CO2 and excess air are all directly correlated

retiredguy

Many years ago, in the early 1970's there was a house in the suburbs of Pittsburgh, Pa that the customer updated with the best windows he could find and tightened the house envelope as tight as possible. My boss at the time installed a new Lennox gas furnace with A/C that summer. When the cold winter weather came the occupants of the house would occasionally suffer from dizzy spells, headaches, nausea, etc. Every service tech we had plus people from the gas utility company and the local fire company visited that house and tested for everything they could with their specialized equipment. Nothing could be found until someone used one of the 3 bathrooms that was rarely used and turned on the bathroom exhaust fan. That small fan reversed the chimney and all the products of combustion from the furnace entered the home. Problem found. This is just an example of how a small vent fan can affect the chimney draft on a furnace. Hope this helps.

EBEBRATT-Ed

Takes about 1700 cubic feet of air to burn 1 gallon of oil

That's a lot of air that has to come from somewhere.

People don't realize how much air a boiler or furnace needs

STEVEusaPA

EBEBRATT-Ed said:

Takes about 1700 cubic feet of air to burn 1 gallon of oil

That's a lot of air that has to come from somewhere.

People don't realize how much air a boiler or furnace needs

Also high efficiency driers can suck all the air out of a 1500 sqft house pretty quickly.
And if the boiler is providing domestic hot water, it’s usually running when someone is doing the laundry.

Big Ed_4

I would suspect improper ventilation to the boiler room . You need from room to room if room large enough 1 square inch of free air per 1,000 BTU input ,or two vents 1 square inch per 1,000 BTU input for fresh out side air . They make Air in a Can which will work if any problem . . Exhaust fans can also be the culprit ....

STEAM DOCTOR

Check boiler for leaks. Water dripping into flame can certainly mess with proper combustion. 

captainco

An old furnace with a drafthood is not connected to a chimney and is more susceptible to house pressures, but an oil furnace is connected, However, when the burner is operating, the burner fan can overcome almost any negative pressure such as a fan. But when the burner shuts down the negative pressure has a major affect on the equipment. The draft will cease immediately and the heat will radiate back into the burner tube and cause what I define as delayed afterdrip. This will cause the flame cone to start sooting and the the combustion gets worse,

Just for the record I like to throw this out for thought. If l gallon of oil uses 1700 cubic feet of air an hour, how much does it use in a minute or 15 minutes? That is 28.3 cu.ft. per minute or 425 cu.ft. in 15 minutes. What are the odds a room is smaller than that? I am not saying a room should be 425 cu.ft. but sometimes we over think the combustion air problem. It is not the size of the room or the size of the opening, it is how are we controlling it? No room ever runs out of air, air just gets misdirected.

EBEBRATT-Ed

Bottom line is there has to be air either from an opening to the outside or from infiltration

Joseph_4

I appreciate everyones's comments. I thought i did proper diligence last year. I asssumed all was ok because they told me they had no sooting up before they called me , in june 2020, in13 plus years with little yearly maintenence. This year i noticed they have a webster pump on a beckett chasis afg, which i checked the pump pressure THIS time and its at 100psi with the nozzle size being a .85 when manufacturer calls for a1.25. I will be going back there today. i cleaned it all up and replaced chamber. hosed it down to clean out all soot about 30-40 times. Can I assume the reason my air is so high is because the nozzle is very undersized?
This still wouldnt explain why it lasted 10 months or did the small fan cause its slow demise
Thanks
Joe

EBEBRATT-Ed

Adjust the burner to a trace of smoke and take a Co2 test. Then increase he air until the Co2 drops 1 point. So if you get say 12% with a trace adjust the burner until your at 11%. This gives you a cushon to prevent sooting.

Maybe the oil changed

Maybe drop the nozzle size and increase the oil pressure to 130 to give it a better fire

Joseph_4

The nozzle that was in there was a .85 at 100 psi. manufacturer wants 1.25 at 100 psi.. i was getting 02 at 6.. on the chart Robert provided at 12% co2 i should have 4.6 O2.. is the discrepancy because a small nozzle is being used in a bigger chamber?
Thanks
Joe

Steamhead

Could be.

The current version of that boiler is the WBV-e-04. That boiler is offered in firing rates of 0.95, 1.25 and 1.5 GPH. All these models now use higher pump pressures- 140 on the Beckett AFG. For the record, it's 170 on the Beckett NX, 150 on the Carlin EZ-1 and 155-160 on the Riello 40-F5. The burner spec sheet is here:

https://www.peerlessboilers.com/wp-content/uploads/2017/12/WBV_burnerspecs2.pdf

And of course, you've checked the burner head and static plate to make sure they're correct, and that the nozzle is an 0.85x80B.................

What I'd do is turn your pump pressure up to 140 PSI using the 0.85 nozzle, re-tune it and see if that helps. The higher pressure will produce smaller oil droplets in the spray, giving better combustion, and the slightly larger fire should eliminate stray air currents in the firing zone. See @Firedragon 's book "Advanced Residential Oilburners" for an in-depth discussion of this.

Let us know how you make out.

EDIT: Whatever setup you end up using, always put a label on the burner showing the nozzle spec, pump pressure and (if different from the usual) head spec and static plate size. This makes it easier for the next tech to maintain your work. We label all our burners this way (and use at least 140-PSI pressures too). An old-school DYMO labelmaker works great for this.

Joseph_4

thanks steamhead.. the only label on that boiler said 1.25 didnt give other options, but i see as they sell today its as you say, the webster pump says up to 3gph at 100 psi.. do you know if its made to run at 140psi?
thanks
Joe

EdTheHeaterMan

That pump will operate at 140 PSI. The max GPH will be somewhat less at that PSI.

Mr.Ed

Steamhead

It should- most are. When you set the pressure, make sure it remains steady- it should not rise and fall. If it does, replace the Webster. When replacing, I'd use a CleanCut unit that contains a solenoid valve to delay the introduction of oil to the nozzle until the airflow, oil pressure and spark are established ("Valve-on Delay"). This results in cleaner starts and stops. If using a CleanCut without a PD (Precision-Delay) Timer, you must use a primary control that has the delay built-in. Let us know what control is on that burner and we can advise you.

I realize all this sounds like a lot, but this is how we bring oil burners into the 21st Century. The end result is much less cleaning needed the next time, and better efficiency over the course of the heating season.

Joseph_4

ok thank you to all.. will let u know how i make out
thx
joe

Joseph_4

so i went today. raised pump pressure to 140 psi. with the old nozzle, was a 85 80a, could not get a zero smoke with air below 6 percent. I changed the nozzle to a 85 80b. That wouldnt allow a zero smoke without air being 7 percent. The c02 was 10.3 percent.. that is How i left it for now. I installed a new barometric draft control still, The overfire draft is zero ..at breaching it was mostly at -02. sometimes -.03.
What do I do for these people? with these numbers are they guaranteed to have problems of future sooting in future?
Thanks
Joe

Ctoilman

The numbers are fine, but I would be inclined to use a smaller .75/80A nozzle.  How are you reading zero smoke by the way?  Smoke tester right?  I use a minimum of 12 pulls across the paper.  

EBEBRATT-Ed

@Joseph_4

Putting in the "recommended nozzle" is half the job. Most all boilers can be downfired one nozzle size without any ill effects.

Your not going to have good success with the overfire draft at 0

If the chimney and flue are in good shape and clear (have you checked that) and the boiler is clean and you don't have over fire draft what do you do?

When you pour water into a funnel and it overflows do you keep pouring or stop pouring? You stop. So reduce the burner input

Leave the oil pressure at 140 and try a smaller nozzle, less input = more draft

and make sure the burner has the correct head and static plate for the firing rate your at........not the nozzle size.

How is the burner head? Clean, burned off or warped??

Joseph_4

I checked the chimney the head and nozzle.. Burner not warped or burned off. The smallest nozzle size the boiler manufacturer recommends is .85 at 140 psi as Steamhead pointed out. I Understand Ed-EBEBRATT's solution. but it brings me to a problem I have had for years understanding oil boilers in general. I've been taught not to underfire a boiler more that 10%. How is it possible that the same size cast iron Boiler can can be fired with a .85, 1.10, and a 1.25.. Why is .85 not considered underfired compared to 1.25 size? The solution to use an even smaller nozzle wouldn't it be even more underfired?
This may be a stupid question, but if I put in a new boiler sized according to house's heating load.. If this one was originally sized properly, would they still be having the same draft issues?
Thanks
joe

EBEBRATT-Ed

@Joseph_4

Following the manufacturer's recommendations on set up is always the first place to start.

But there comes a time when your beating your head against the wall and it;s not working what are you going to do? What you have to do is throw the book out and come up with something that will work. Are you sure the boiler flue passages are clean? The chimney is unobstructed?

You can't put more fire into the boiler than the chimney will take.

Downfire it. You combustion test will tell you the story.

If you have a little more draft, decent CO2 and 0 smoke then you should be ok.

I have had both Power Flame and Carlin burner where the factory set up simply didn't work. There are countless jobs like this.

Carlin came out and tried different nozzles until they found a set up that worked.

Contrary to what some beleive oil burners are not an exact science.

Draft changes
Fuel changes
Fuel temperature changes
Combustion air temperature changes
The temperature in the combustion chamber changes

Your looking to keep the burner in a safe range, not hit exact numbers

mattmia2

remember that .85 nozzle it .85 gph at 100 psig. at 140 psig its firing rate will be significantly more.

Ctoilman

mattmia2 said:

remember that .85 nozzle it .85 gph at 100 psig. at 140 psig its firing rate will be significantly more.

Yes, at 140 psi fuel flow increases by 18% compared to the nozzle rating.  For example, a 1gpm nozzle will deliver 1.18gpm of fuel flow at 140 psi.

Big Ed_4

Rule of thumb you can down fire 80% of the firing rate ...

Burner ran fine for years now there is a problem. What changed ? Did they finish off the basement ?