outside air ?

Hi,
New here and I've got a question about the introduction of outside combustion air.
I have a Harman Mag.( first time use) along with an oil boiler with a power venter. I don't know if I'll have an issue or not but my question is ;
When folks cut in an outside source , how do you "combat" the infiltration of cold air ? ( may sound dumb... but I'm curious )


My house is relatively "tight" .

Thx, Mossy Beard

Most people will run PVC pipe (or flex) directly to the combustion blower and make an adapter to the blower. ON the outside, you can use like a dryer vent without the flapper) or something that will keep the critters out.

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My house was built in 1975, is by no means air tight & since my stove is in the basement family room, I find there is enough outside air infiltration that I don't need to deliberately add any outside air. If your house isn't "tight as a drum" you may find the same thing.

The "air filtration" make up method may not be in your best interest!

What if your stove is drawing air from say the stack of your hot water heater -or the dryer vent - or from the stove vent... of what if the infiltration is on the opposite side of you living space from the stove / boiler / furnace

Now you get to live in a cold draft..

Bring in plenty of dedicated outside air and defeat the infiltration to the appliance.

Mossy Beard wrote:My house is relatively "tight" .

That is a very good reason for outside air for the combustion draft right there.

What Sting says is very true plus, why burn air that you have already paid to heat. That said all houses need to exchange the air, the idea is to control the air exchanges and keep heating as economical as possible. I have never worried too much about outsice air on the heating stuff because appliances like dryers draw a lot more air than a furnace though not run constantly. That and there is no easy way to connect a hand fired stove to outside air

I believe that bringing outside air for combustion will reduce drafts in your house. I called Alaska on this and was told that it would lower the efficency of my stove. Others have said that is baloney. I guess I'll never know until I pop a hole into the side of the house. You can buy 3"aluminim flex pipe for under 10.00 which will make the job of running the pipe a snap. Just remember to add a screen at the end of the pipe. I was also told not to seal the pipe to the stove just in case the pipe becomes clogged.

Frank

Depending on the size of your combustion appliance, the International Building code, which is part of many building codes REQUIRES outside combustion air. Small stoves that can draw air from large areas like a whole basement might meet code without the outside air.

All good points.
I have to look further into "how to adapt a 2" or 3" pipe to the Mag. combstion blower and make the whole thing look good....
This area of the basemant is finished, to my lovely wife's specifications.
My concern is NOT to have a bunch of cold air leakage caused by "not so positive connections" ?
As stated previously, I have a power venter on the oil boiler, which will run at times.

I'll have to pipe it all up in something 'pretty' until it enters my suspended ceiling, above the stove. ( maybe small black stove pipe, or painted PVC)
I guess I could run it along an adjacent wall, at the floor to enter an unfinished space ?

Another question that came to mind is;
What distance would you suspect that little fan will draw ? ( duct run)

Thx, Mossy Beard

Think of your house as a sealed box.. when your stove is running, the amount of air going up the chimney has to leak into the box to make up for the volume of air going up the chimney...
Now. toss a load of clothes in the dryer,, that big fan is forcing air out of the house, then turn on the exhaust fan in the bathroom.. and maybe the exhaust fan in the kitchen.. now your house is under a significant vacuum.. and the strongest fan wins... I'd guess the clothes dryer.. so, where does the 'make up' air come from?? There can be enough vacuum on a 'tight' house to REVERSE the airflow in a chimney.. and pull the coal exhaust into the room and the house..

Every year we have a few forum members who get CO warnings unless they open a window or saw a 1/2" off the bottom of a door.. to provide an outside air source.

I would not seal the outside air source vent duct to the inlet of the combustion fan.. if you have a lot of snow, or leaves or whatever block the outside inlet to the duct, the stove will starve for air, if you end the duct just a few inches from the inlet of the fan that will suffice.

Once you have the duct installed, try this 'science experiment'.. light a candle to show air flow.. put it near the outside air duct.. have someone turn on the clothes dryer, the bathroom exhaust fan and the kitchen range-hood exhaust fan.. and take a look at the increase in the air flow through the duct..
I did the above 'experiment' many years ago in a not very tight house and was amazed at the amount of air being pulled into the house to make up for all the exhaust fans... And my rooms at the far end of the house became much warmer because the lousy windows in those rooms were not leaking cold air into the house whenever an exhaust fan or the dryer was running..

Greg L

Once you have the duct installed, try this 'science experiment'.. light a candle to show air flow.. put it near the outside air duct.. have someone turn on the clothes dryer, the bathroom exhaust fan and the kitchen range-hood exhaust fan.. and take a look at the increase in the air flow through the duct..

What works even better then a candle and no where near the price of one of those smoking pens is a simple incent stick, they give off a constant smoke and are very lite to move around the house while you are investigating air loss/gain.

Steve.N wrote:That and there is no easy way to connect a hand fired stove to outside air

Good point.

The International Building Code requires two outside air openings, one within 1' of the ceiling and one within 1' of the floor. Each opening area should be 1 sq in. per 4000 Btu input rating. I've oversimplified the requirement and there are other details. Look up the details in the code, Section 701

Devil5052 wrote:

Steve.N wrote:That and there is no easy way to connect a hand fired stove to outside air

Good point.

Not exactly correct.. a hand fired stove is still pulling air from the room and house it is in.. provide a duct that ends under the hand feed stove.. the fresh air will supply the air to the hand feed firebox through the same air inlet with it's air control you have now. The source for fresh air to the stove will now be primarily from the duct instead of all the window, door and foundation leaks...

It works.. trust me !!

Greg L

LsFarm wrote:Not exactly correct.. a hand fired stove is still pulling air from the room and house it is in.. provide a duct that ends under the hand feed stove.. the fresh air will supply the air to the hand feed firebox through the same air inlet with it's air control you have now. The source for fresh air to the stove will now be primarily from the duct instead of all the window, door and foundation leaks...

The problem is that if your hand fired is situated like mine (see pic below)in a finished room where it must pass the "wife test" it would require a rather unsightly "Rube Goldberg" duct to end up supplying the outside air to the lower ash door air inlet. (mine is on the cement basement slab so it's inaccessible from underneath) If you have any suggestions for my setup Greg, I'm wide open to ideas. (as it is now, I just keep the window (beside the stove) open a crack, except on the coldest days.