How air affects the boiler combustion, this Friday's case

RayWohlfarth

In this weeks video, a contractor sent me an email saying the boiler sooted. He sent me the combustion readings and they were nearly perfect. He adjusted the air to fuel ratio when it was 12 degrees outside for 15% excess air. The boiler used combustion air directly piped to the outside. It will air Friday at 6am EST

Steamhead

Oil or gas? If gas, atmospheric or power burner?

JUGHNE

Where was the sampling done in the exhaust piping??

EdTheHeaterMan

cold air is more dense that warm air. so there is more oxygen in the cold January/February air per cubic foot (fans move air in cubic foot per minute) than there is in warmer air you may find in September /March air. so the combustion air when the burner was adjusted may have had just enough oxygen, but as the weather changes and the temperature increased over time, the oxygen was not sufficient for complete combustion.

Also as a fan gets more dirt accumulation over time, you will also move less CFM. without making a combustion air adjustment for the dirty fan or the lower oxygen content, you may get soot to form as a result of incomplete combustion.

PS. Ray did you get the vacation film developed yet? Would love to see the grand kids!

RayWohlfarth

@Steamhead Its gas and a power burner

@JUGHNE The calibration was done outside and the testing was in the exhaust pipe, about a foot away from the boiler outlet

RayWohlfarth

@EdTheHeaterMan I will post pics on friday Thanks

Steamhead

Chimney got blocked?

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1809000#Comment_1809000

Double swinging barometric should swing out and allow the system to still burn normally, no? Or worse case, the spill out switch on the damper should've tripped.

EdTheHeaterMan

Here are my vacation pics Ray

Precious times that these kids will always remember!

EBEBRATT-Ed

What @EdTheHeaterMan said. Air is more dense at lower air temps and thus contains more 02, burner fan handles more air.

You have to set burners up with a cushion. When you get the #s you want increase the air to lower the Co2 by 1%

Steamhead

https://forum.heatinghelp.com/discussion/comment/1809005#Comment_1809005

"Should" is the operative term here.

RayWohlfarth

@EdTheHeaterMan nice pictures my friend Looks like you had fun In any event, you were right. The tech adjusted the burner during the cold temperatures and when the weather warmer, they wasnt enough O2 and sooted the boiler. The video talks about how combustion air temperature affects the air to fuel ratio.

https://www.youtube.com/watch?v=Mw8-hkcNTEg

Here are the beach pics with grandkids I even saw baby sea turtles born. That was pretty cool There's even a pic of a beach whale (me)

EdTheHeaterMan

Myrtle Beach… not far from my new home in Charleston! Looks like a good time RAY!

Steamhead

Interesting. This is the opposite of what I was taught on oil.

When setting up oil burners during summer, we're taught to find the point of zero smoke, then add a bit of air to drop the CO2 by one percent. This allows for colder oil, which does not atomize as easily, as well as colder air which is more dense as you say, therefore the fan may have trouble moving it. For more on this, check out @Firedragon 's or @Alan R. Mercurio_3 's training materials.

Did this tech leave any sort of margin or cushion when he set up that burner?

RayWohlfarth

@Steamhead I recommended adjusting the air for 5-6% o2 on the coldest days In that way it will not soot as the weather warms

@EdTheHeaterMan Charleston is on my bucket list I would love seeing some of the older homes

Jamie Hall

Nice show. But… may I be permitted to mention that us pilots have been playing with varying the mixture on piston engines for a century or so, to compensate for changes in density altitude (a combination of air temperature and elevation above sea level)? And that modern automotive engines do that with computer control (those pesky oxygen sensors…)?

JakeCK

https://forum.heatinghelp.com/discussion/comment/1809138#Comment_1809138

Charleston SC is beautiful. When you make it be sure to visit the battery. Lots of historic homes. Also check out the market. And finally maybe go to dinner and forget where you parked so you get to explore while looking for your car.

RayWohlfarth

@Jamie Hall Nice way to show off LOL A few years ago there was a product on the market using auto O2 sensors to adjust the gas pressure sorta like a poor mans O2 trim system Not sure if they are still in business.

@JakeCK Im afraid I would never leave if I go there. LOL

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1809139#Comment_1809139

They (cars) also have a barometric pressure sensor. Even going back to the mid 1980s.

JakeCK

https://forum.heatinghelp.com/discussion/comment/1809149#Comment_1809149

Believe me I'm tempted to stay everytime I'm out there. There is something about walking through those old historic neighborhoods at night. Many still have working gas lamps.

The beaches are nice too. Isle of Palms is really nice, that is where we normally stay, or close by. The first time my son touched the ocean was there.

The biggest problems are the threat of hurricanes and the humidity.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1809138#Comment_1809138

Do you find the point where CO starts going up if you reduce the air further, then check your O2/CO2 level and go from there? I've found that different burners, or the same burner in different boilers, sometimes have different "tipping points".

EBEBRATT-Ed

Most people when they think of Co they think not enough air. But too much air will "chill" the flame and give you high Co as well.

You can have two identical boilers and two identical burners in the same boiler room and not get the same test results.

Bob Harper

To get more reliable, repeatable performance, consider a makeup air heater. Tempering the incoming air can level out performance. Warming the air should reduce the Rh%, too.

A fire investigator's handbook states that every 20C increase in temp. doubles the reaction rate of combustion.

Modern woodstoves incorporate an air warming system to improve combustion efficiency and decrease emissions. Homeowners think it's just there to help keep the glass cleaner. That's just a side benefit exploited by marketing guys.

The EPA certification process uses warm room air and the test wood is at a consistent moisture content.

If you don't have your draft controlled properly, the draft pressure may drop as the outdoor air warms. This is where having tight joints in your connector pipe can assist a baro. with keeping a steady draft pressure. Make sure the valve plate/ gate on the baro. doesn't stick but swings smoothly. You can lubricate it with graphite.

SlamDunk

We had three, natural gas , 600hp , industrial power burners begin, out of the blue, to soot up the the combustion chamber with 6"+ of soot even though the combustion numbers looked good after we cleaned them out and checked. Our boiler company recommended replacing the blast tubes on the burners. So, we did and the problem went away. I couldnt see anything wrong or damaged in the old blast tubes but the new ones were slightly redesigned. They were quieter too.