combustion/makeup air question....

Alan

Boilerpro -

This thread keeps expanding in different branches...ex

I did not take into consideration the drafthood, which would pose a problem in most passive combustion air supply schemes.

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Boilerpro - Never mind. I downloaded a manual for the Series 2 Burnhams and found a diagram and explanantion of the vent damper operation. Ours obviously does not have one, which others may have assumed when they suggested it shouldn't be a problem having a passive air supply tube for the enclosed boiler room.
I'll have to look into installing one on ours.

Thanks for mentioning the vent damper.

Alan

Alan

I am not clear on one aspect of introducing outside makeup air for our Burnham gas boiler (series 1A).
The boiler is in the basement utility room against one corner of the house, where it would not be too much
trouble walling in the boiler and providing makeup air through one or two 6" diameter tubes (metal).
There is also a hopper window that would be part of the enclosed area.
However, I am concerned with the air temperature during the winter and the humidity level during the summer if the boiler is
set for indirect hotwater heating, which is part of the plan.
Can someone point me to a source where I could read up a bit more on this topic ?
If the outside temp is reaching single digits, which happens in our area, the temp would be fairly low even after it
enters the enclosed boiler room.
Anyway, I'll stop and wait for guidance.

Thanks !

Alan

Dana

There are so many different ways of introducing make-up air. You could use air from within the building by simply installing a means for air to permanently be available to the boiler through louvers cut into the door or walls connecting the boiler room with other sections of the house. The requirement for this method is 50 cubic feet of air per 1,000 btuh of firing input. If you connect directly to the outdoors, its 1 opening 12" from floor and 1 12" from cieling based on 1 sqare inch per 4,000 btuh based on the additional air you would after figuring the air available in the boiler room based on the 50 cubic feet per 1,000 btuh as stated above. You can also introduce ait with a device call a Fan in Can, whish is connected outdoors thru 1 piece of pipe, 4 or 6", depending on btu load. This is wiried into the contrlo package on the boiler and pulls air into the boiler room only when the burner needs to fire. It is interlocked to the burner so the boiler cannot fire unless the fan has prooved it is running. There are other ways as well, too numerous to mention. These are the most common. Local codes wherever you are may differ. You can see the fan in can at Fields Controls Website. What you don,t want to do is introduce to much cold air or introduce it ia a spot where ir directly impacts water or heat lines. I have yet to see a boiler room freeze up in any way due to make-up air if its introduced with thought to the above.

Alan

thank-you; followup Q

Thank-you, Dana, for the btu/cu.ft figures, which I will double check against what the local code requires.

Louvered doors is out of the question because on the other side of the utility room is a second family room.
Outside makeup air is the route I want to take.
Although I'm not concerned about freezing conditions in the boiler room, even the Fan in the Can is introducing
outside air when the boiler is running, thus the possibility of humidity or low temperatures becoming a factor
in the efficiency of the boiler - or am I getting bogged down with the wrong concerns ?
I have all the pipes insulated around the boiler already, so my main concern is the low air temp or humidity level
of the makeup air. I am not sure how much of a factor this is on a gas appliance.
There must be folks up North who see many "passive" makeup air configurations - if the temp/humidity level is not a major factor
in the combustion efficiency, I could start out by piping in the air and enclosing the boiler in an appropriately
dimensioned closet. The wall next to the boiler is an outside wall, so the piping would be minimal.

Maybe I'm worrying about the wrong thing.

Thanks for your reply,

Alan

Unknown

Alan get in touch with me

by e-mail and I can help you with a set up that will minimize cold air intake on your air for combustion problem.

Dana

Tim, if you have a set-up I would love to here about is as well. Dana

Mark A. Custis

Combustion make up air

Alan:

You got to do it if the boiler can beat the can fan. I use a very inexpensive thermal trap to control combustion make up air. Imagine a pipe in a wastebasket. The cold air stays in the bottom of the waste basket and cuts off the flow of air until the boiler wants to breath, and then it only allows enough air into the room to meet the boiler needs.

I have a six inch air intake from outside to the return air drop on my forced air equipment, and thermaly trapped intakes big enough to feed the boiler room and the needs of the heat pump's gas fired airhandler. My air handler runs24/7. The outdoor air to the return air side of my sheet metal pressurizes the home (take that you blower door guys) so I only have exfiltration. The combustion needs are fed by the trapped intake.

Never have a problem with tempurature or humidity in either heating or cooling.

Timmie is a man of his word. Take him up on his offer.

Mark

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Alan

Thank-you all

I appreciate all of you taking the time to reply to my post.
Tim is sending me information to help steer me in the right direction.

As for Mark's comment:
"I use a very inexpensive thermal trap to control combustion make up air. Imagine a pipe in a wastebasket. The cold air stays in the bottom of the waste basket and cuts off the flow of air until the boiler wants to breath, and then it only allows enough air into the room to meet the boiler needs."

This kinda makes sense to me - I'm guessing the room is pressurized and keeps the outside air at bay until the boiler starts breathing. I'm interpreting this to mean for this to work, the boiler room would need to be fairly well sealed up and airtight except for the opening for the makeup air tube that is properly sized. Some cold air would enter but not continuously.

However, my concern is while the boiler is breathing it is possible the combustion air would get extremely cold during an extended run. Likewise with humidity level during the summer. This I haven't figured out how to address.
I guess it is possible the running boiler could be offsetting the cold temp of the air makeup air and I am getting bogged down on this detail unnecessarily - I would be happy if someone told me to just drop it.

I have read articles showing two 6" tubes, one closer to the ceiling and the other terminating withing 12" from the floor.
But for the pressurized setup to work, there should be only one tube.....

Anyway, I will carefully digest the info that I gather and proceed cautiously.

More specific examples, ofcourse, would be appreciated.
I am hoping for a fairly passive setup that does not require any electronic controls that is coupled to the boiler but without the danger of starving the boiler of combustion air.

Thanks again,

Alan

hot_rod

There are some other options

A fairly new revision allows only one opening near the ceiling NFPA A 5.3.3(b)2 (1 square inch per 3000 BTU/hr. input)

"The second method addresses the concerns to reduce the combustion and ventalation requirements to reduce freezing water pipes and limit low temperatures in the equipment room"

I believe the International code has a similar wording. Find out which code is used in your area.

Personally I prefer sealed combustion equipment to get away from combustion air grills into the mechanical room. Keeps the boiler from breathing undesireables that may be stored near the boiler, also.

hot rod

zeb_3

Comb. air

I have used Tjernlund's "Inforcer" w/ good results. It is a motorized fan that draws outdoor air through 3" pvc and mixes it w/ room air to temper it. Check out their sight.

Alan

Thanks, hot rod -

I guess my idea is to close in the mechanicals and keep it nice and tidy in there....
No flammables would be allowed in the room.
Sealed combustion would be nice, but the Burnham is humming away nicely for the time being.
If it is possible to pipe combustion air to the boiler directly, I would consider that option.
Not sure if that is possible with a Series 1A cast iron boiler.
(I have seen pictures posted here showing such Burnham installations.)

Yes, the single opening theory is making more sense to me.
I will read up on the regs when I receive them.

Thanks again,

Alan

Alan

Thanks for the "Inforcer" info.
Although I am aiming for a passive setup, I am interested in reading up on this setup.

Thanks again,

Alan

Steamhead

Me too, Tim

always glad to hear your ideas.

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Mark A. Custis

Humidity control

Let me try again:

Close the door from the family room to the boiler room. If the boiler is off the room should be the same pressure as the rest of the house. Install a passive intake with a thermal trap and nothing happens the room will be the same pressure as the rest of the home. Fire the boiler, now the draft from the boiler will bring air in through the passive intake.

The air mixes with the burning fuel and goes up the stack. It will not affect the rest of the home. The termal trap is like opening and closing a damper. No burn, no outside air. I try to locate the wastebasket on the floor as close to the burners as practicle.

If you are afraid of passive infiltration don't be, unless you have a home running under negative pressure. The only time air comes in is when the burners are firing, and at that point there should be enough heat in the room to prevent freeze ups.

If you are intersted in being slightly more in control check out the Arzel Zoning web site. They make a damper assembly that will "seal" the air intake. Or check out Skuttle Manufacturing in Marrietta, OH, they make a thermal trap intake you just mount and forget. They also make the outside air to return air equipement I pressurized my home with.

If you need more please let me know.

Mark

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Alan

Howdy, Mark -

Everything you say is making sense now, and thanks for your patience.

Two questions.

1. I am not clear on "I try to locate the wastebasket on the floor as close to the burners as practicle.".
Some information I'm getting is the single wall opening should be near the ceiling of the room.
Are you piping the air tube from there closer to within 12" of the floor as I have read in some articles ?
If so, is the tube dropping down into a wastebasket fairly close to the boiler intake ?
I'm trying to picture this setup....
(The boiler is close to the outside wall, so none of this should pose a problem.)

2. As for the thermal trap damper, I guess this would be the horizontally swiveling type that is slightly weighted.
It would swing open when air is drawn in by the boiler.
If there are specific types I should look at, I would appreciate some guidance.

Thanks again,

Alan

Alan

Thanks, Zeb - I looked up the info.

Zeb - The "Inforcer" may have a place in another house where a oil burner resides in the middle of the basement.
The smallest unit would be the ticket.

I'll keep it in mind when that boiler is closed in.

Thanks for the tip.

Mark A. Custis

Check this out

This works if your home is either neutral or pressurized.

This is a cheap, effective, low upkeep way to do what you need to do.

Please feel free to contact me if you have any additional questions or are in need of additional clarification.

This is what I have in my mechanical room sized for all appliances burning at once. The barometric damper assembly you reffered to is what I have on my sheet metal system. It too, draws in outdoor air, but this air is for people plants and pets. They make me go outside to breath.

Mark

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Unknown

Alan what I am sending

you explains what Hot rod posted and gives you the step by step procedure for sizing. The single opening was the result of a study done by GRI (Gas Research Institute) and a company named Batelle in 1994. It became a part of National Fuel Gas Code in 1996. It is also in the 2000 International Code and the new 2002 National Fuel Gas Code. I will be in the mail tomorrow.

hot_rod

One concern with \"high\" only

is in LP fired equipment. As you know LP is heavy and settles to the floor. With a high and low opening their is a path for a LP leak to vent.

With high only... ??

A LP detector is a good idea in either case, although they do false alarm from various other "smells" ocassionally.

hot rod

Unknown

Dana & Steamhead

it is nothing mind boggling. It is the single opening system tested by GRI and Battele back in 1994. I have used it in several situations that had problems with pipes freezing in extreme cold weather.

I have a guide on "Air for Combustion" that includes the procedure with some drawings.

Steamhead I will send you one. Dana I am not sure I have your address e-mail me and I will get it out to you.

jim f

DANA, ran into that a couple of weeks ago. 2 cas-6 fans in a can with 10" pipe to each can positioned on a hanging platform feeding air to 2 burnahm 904 boilers 980,000 bth total. thermometer in room read 23*. outside temp over night went down to -15*. needless to say pipes coming in from the well and all surounding the area frozen solid. we heat taped the pipes with a t-stat for now. did not know what to do at the time.
jim f.
milford, ct.

Boilerpro_2

Another suggestion..

If you have a standard atmospheric draft hood equipped boiler without a stack damper, I'd put one in. My father had an apartment building with a big million btu plus draft hood boiler and a big air intake in the wall. Freezing was a constant concern. Installed a stack damper on the 12 inch vent and from then on the boiler room almost never dropped below 100F.

Boilerpro

zeb_3

No problem, that is why we hang out here. n/m

Alan

stack damper...

Boilerpro -

Would you mind elaborating on this a bit more ?

Is the stack damper is installed on the makeup air vent ?
My apologies for asking this - I'm trying to picture the setup you're describing.

Thanks for your post.

Alan

Boilerpro_2

Stack damper on boiler flue,

not on air intake. If you close the chimney vent, the amount of air entering the boiler room through the open air intake is reduced dramatically. The chimney is drawing air out of the room whether the boiler is firing or not, so closing this vent during the off cycle helps lock heat into the boiler room.

Boilerpro

Alan

ok....

re - The chimney is drawing air out of the room whether the boiler is firing or not,

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This makes sense.
Does this mean.....the positive pressure theory mentioned isn't necessarily so ?
Our Burnham gas boiler is equipped with a draft hood, which will probably cause cold air to enter the room through the makeup air vent even when the boiler is not running.

Is this "chimney vent" or draft damper passively closed or is it triggered by a control when there no demand for heat ?

Boilerpro_2

Damper operation..

It is a motorized damper. When the boiler needs to fire, first the damper is opened and when the damper is fully open an end switch is made to fire the boiler. They are basically standard issue on newer atmospheric gas equipment with drafthood in order to boost the AFUE rating of the boiler (worth about 8 to 10% boost in AFUE rating).

Boilerpro

Boilerpro_2

BEfore installing stack damper...

be sure the gas train is up to snuff. Equipment with stack dampers require redundant gas valves and probabaly spill and roll out switches.... call an expert for the modifications.

Boilerpro

Alan

re - call an expert for the modifications.

------

Thanks for the warnings.
Certainly don't want to create a dangerous situation.

Alan

THANK-YOU, Timmie !

Tim -

Received your packet the other day.
I appreciate you going out of your way to help me out, in particular with the inclusion of "Air for Combustion" textbook for your seminars.
(If there is an opportunity to take advantage of the classes you offer I would love to sign up.)
And thanks for the yellow stick-on notes identifying the chapters that cover the topics mentioned on this thread.

As Mark Custis pointed out earlier, "Timmie is a man of his word. Take him up on his offer."

With sincerest gratitude,

Alan