What Do U Think Abou O/S Combustion Air? Long Post, Sorry

Hey fellas, I am new here, but have played with coal for a while, I am a "heating pro" and always tinkering...

I will start by explaining my homes heating system (s).
First the house is built in 09, 2x6 construciton, well insulated, BUT 4200+sq feet, 9ft ceilings throughout with some as high as 24ft... My primary heating system is a mod con boiler (LP) running water to hydro coil units {delta T, outdoor reset, variable speed fans, the works}, with a Heat pump auxilary on all hydro zones {so electric heatpumps work down to 45 degrees before the LP kicks in}, an OIL fired G115 backup boiler {if my LP is out and there is no heat in my coal stove the oil kicks in}, and a Reading suquahanna coal furnace is my alternative heat source {wired so when my coal furnace is 10* above ambient temp all other systems are shut down}.... For DHW I use a Rinnai tankless condensing water heater in the winter months and an AO smith hybrid tankless in the summer months.... My house is like my showroom, I have waltzed many customers in and showed them the systems before they purchased... {rite now I am repiping most of the central system to allow for 2 more zones so the coal is the only system up and running, and I started thinking "how can I make it a little better"...

Now for my coal system, its a big reading unit with the coal-trol, I have it ducted into my homes duct work with its own return, I have a swg4 power venter, with a speed control turning it as slow as I can while maintaining safe draft... I burn a few tons a year, but we keep the house warm borderline hot, its much cheaper than lp or oil or electricity obviously, and while I didn't spend a ton of money on my stove {I couldn't justify spending twice the price for a furnace that did basically the same thing, the un-insulated jacket was not a deal breaker for me since the stove sits in heated space...} it works very good...

So anyway now onto the point of this post, I am tinkering and tuning, and want to rig up an outside combustion air system, I am thinking sched 40 pvc, ran to each burners intake and then ran to the outside with a critter gate and basic intake termination kit... This will stop the unit from taking my heated air and blowing it outside, plus I will be able to shut the door completely to the furnace room {I don't do this now because its pretty tight and it changes the coal fire when I do, not enough combustion air after a while}......

Has anyone done this or played with the idea? any comments and ideas are welcome, thanks a lot...

Many of us have done it. I put two 4 inch dryer vents in my boiler rm door that goes to an outside air storage rm. Major difference and I had to readjust the settings on my stoker and baro. There is a thread here about the amount of oxygen(in gallons) that is required to burn each lb. of anthracite. Do a search for threads of this nature and read to your hearts content.

Kevin

...welcome to the forum!

...sounds like quite a house!
...personally I think you may need one more heating source-like wood !

...kidding aside...make up air for combustion is an EXCELLENT idea...just do it right

...now take a chair and a beer+ cause opinions vary!

no matter what,you are burning outside air...directly or indirectly,through leaks in your house or opening doors or windows,or you would end up in a vacuum.if you pipe it in directly,you are being much more efficient

Thanks guys, when I built my house I cleared 6 acres, and figured I would put some wood inserts in or an outdoor woodstove, until my wife seen the piles of wood and started doing the math on how long it would be sitting there, she quickly put the brakes on that idea, now we have 3 lp gas inserts that would cost me a fortune to run, lol.....

I am going to do a little measuring in a few minutes, then I am going to fabricate a sheet metal collector for each burner and either use pvc or maybe some flex hose would most likely be much easier, but I have to keep the aesthetics in mind since I have customers come here pretty often so an octopus of dryer vent may look a little "backyard mechanic, while it would most likely be much easier and work better since the bends would be less intrusive... Ill see what I can get to happen...

fifthg, yes that is the plan, I have had this conversation with a few old timers in the business, and they prefer inside air, but the issue is, no matter what its coming from outside, you are not going to get your house under negative pressure with a draft inducer, but I would much rather burn unheated air than air I payed to heat, its all going back outside, and IMO the combustion is better with cold air {I spend a lot of time looking at fires, lol}

Thanks for the replys keep them coming, I lover conversation..

cloud9
..you may have missed an earlier thread about vacuums....they are unachievable !

...with that said...relative to the air outside...it IS totally possible to have 'lower' pressure inside (especially a newr 'tighter' home)
...you even speak of the affect in your furnace room when you close the door-same idea.
bathroom exhaust fans...clothe dryers...stove exhausts....all add up when it comes to 'evacuating' the home of air.....and it all gets made up by outside air-eventually.
how and where it gets made. can be dictated...creating a more comfortable (aneven healthier) living space

My house is VERY sealed I have 2 -aprilaire 8100's so the conditioned inside "stale" air is exchanged with fresh outside air at certain times of day and intervals but done so by only losing 23% of the energy in my conditioned air, if that makes sense to anyone, lol... I run them very little and have IAQ sensors that control everything {essentially a carbon dioxide meter}. So when my coal furnace sucks air from inside my home and blows it outside its not doing me a favor, lol, its costing me money... All of my other appliances use outside air, the bathroom make up air comes from the 8100's, that supplies the fans and the clothes dryer {located inside one of the upstairs bathrooms} as long as the doors are closed of course.... Also the kitchen stove fan is filter and return not exhaust, so really only the bathroom fans and the clothes dryer remove air from my home...

I install high efficiency heating equipment for a living {Own an HVAC-r co} so when we built this house, efficiency was high on the list of concerns, since I contracted it myself, and obviously designed and installed the hvac system, everything is insulated, zoned, and thought of in advance, from DHW recirculation to double handled faucets to insure no nuisance tankless calls... When I built the mechanical room I was thinking about heavily insulating and using a central auto door for makeup air and letting the appliances pull from that room, but then freezing issues could have been a problem so I did it the old fashioned way individually intaked every appliance, which made a lot of holes in the house, lol.....

Anyway I measured a little bit and it is very possible, I am going to make some intake boots, and play with flipping over one of the blowers {the left ones intake is facing the right ones motor and it would be much easier if they were both facing the outside....

Here is a pic of my set up before I connected the flue pipe and fired up. 4" pvc pipe used for combustion air. not pretty enough to show potential customers, but it works.

Is that an autofeeder?

Cut a hole in the wall!

Loosen up your tight-ass modern home boiler room with a louvered vent to the outside. It will increase your natural draft. There is a code formula for air communication between the boiler room and connected rooms, and for outside air also. Forget about piping it to each boiler. No need to do that. The heating units take what they need from the surrounding air, unless otherwise designed. If boiler room draftiness is a problem on exposed piping, baffle the vented air to the floor. Pre-heated air is supposed to be better for combustion but I don't ever remember experiencing any discernible difference between 15* air and 65* air, besides, the un-piped air would preheat in the ambient temperature of the boiler room.

Edit: and btw, louvers in the boiler room door may also be the answer.

mikeandgerry wrote:Cut a hole in the wall!

I kept reading down through this post wondering why doesn't he just add a vent to the boiler room??! You don't have to pipe the air straight to the stove, just let the room breath.

Let me explain why I would rather not add a boiler room vent, this boiler room contains all of my well piping and plumbing headers, when the coal is not running there is VERY little heat in that room, when I am using my mod con boiler the jacket and standby losses are almost non existent, this room contains $30,000 of heating equipment and my well insulated house can go 10 hours without calling a zone in service, for example the T-stats are setback to 55 from the hours of 5am to 4pm, we leave the house at 6am and get home at 5pm and on a 23 degree day I recorded 1 zone calling for 13 minutes... so since the mechanical room has no emitters itself it can get cold enough to freeze, I would rather just not deal with that situation, I know if I use an autovent it will only open when an appliance is running, but the water heater, mod con boiler and oil boiler all use concentric venting so their intake air is part of the termination kit.

I am thinking about using the field combo vent in the future, since my field powervent as a unit I took out of a house used, I figured I would use it until it failed but it has been working fine for years, some day I will switch it to a ss swg combo and then I will have the air feed and the power vent all in one...

I am going to play with the outside air a little this coming week, I have a goood sized job to make all the sheet metal for so I will play with the design while IM stuck in the sheet metal shop...

Rob R. wrote:

mikeandgerry wrote:Cut a hole in the wall!

I kept reading down through this post wondering why doesn't he just add a vent to the boiler room??! You don't have to pipe the air straight to the stove, just let the room breath.

Exactly. All of your heating equipment, and you have almost one of everything, needs combustion air. Starve it for air and you set up conditons that can produce CO. Since your house is so well sealed it is even more important. A 6" vent from outside to your equipement room would probably be about right.

with all due respect...set back temp to 55 degrees has got to be one of the silliest ideas ive ever heard of.
maybe you should spend a few bucks and put a "zone" in the boiler room...
protect the 30 grand worth of equiptment???

I have found the exact opposite of my house ..... This place will call for heat when it's 60° outside! My combustion air comes thru the walls, sills, windows & doors.

Sorry I can't add a thing to this thread ...