Outside Air Supply

[karl]

Attached is a drawing of my fireplace and the wood pass through that sits next to it. I have decided on the PE Summit insert. I'm trying to figure out the best way to provide outside combustion air to the stove. The following paragraph is from the PE Summit manual


Outside air supply: Remove cover from ash clean out in existing fireplace. Place a rodent screen in place of the cover. Install the Insert as described in the "Installation" section, making sure not to cover the opening of the air inlet. When installation is complete, seal surround to fireplace and anywhere else air may enter. This will ensure combustion air is drawn from the outside of the house and into the 9" x 2" intake at the lower rear of the appliance.

Since I don't have an ash clean out, can I cut a small hole in the cinder block of the fireplace and then a small hole in the outside door of the pass through, and then build a duct like i have shown in the drawing? If I do this will I still be able to place wood in the pass through? Also how big of a duct do I need? The above paragraph mentions a 9" x 2" intake at the lower rear of the stove. So, am I safe in assuming I would need 18 square inches of opening? Also, there is no mention of connecting this to the stove. Does the stove just pull air in from the back of it and the hole replaces that air?

 

[builderbob]

Not a stove owner yet, but that is the way I interpret the instructions. They want you to "seal" around the fireplace surround---that would prevent it from drawing any "inside" combustion air. The only remaining source to draw air from then, would be the "outside" vent.

As to how big to make the hole, your best bet is to contact Pacific Energy technical help online, and ask. I forget the formulat for computing area of a circle, but perhaps 6" diameter duct would give the 18 sq inches to approximate the stove opening.

With stove sealed off from inside air, and duct to exterior providing outside air as only source to cavity behind stove, does not seem you would need to connect the outside duct to the actual opening in back of stove.

I may be all wet, but that is just my "cold" impresions from reading PE manual about outsid air.

BTB

 

[builderbob]

If pi times r squared is the formula for area of a circle, then a duct about 4.75 inches diameter would give close to 18 square inches.


Ask Pacific Energy technical how big the outside duct hole should be.

BTB

 

[begreen]

I believe 4" pipe is called for the Summit freestanding stove. The same size should suffice for the insert.

 

[karl]

I figured out how big of a hole I would need, but I was also concerned about cutting a piece of block out. Also with having this intake go through an area where I going to store kindling. Would there be any fire hazzard associated with doing this?

 

[builderbob]

Also with having this intake go through an area where I going to store kindling. Would there be any fire hazzard associated with doing this?

I see your concern now with the routing of the air intake duct through the wood kindling storage area.

The question might be stated as: Could there be hot enough temps flow back out the intake tube, and under/amidst the woodbox to ignite the wood kindling in the storage area?

That would raise the question, what is the likelyhood of draft ever reversing, and instead of flow going up the chimney, and supply of combustion air coming in the intake, the air goes out the intake and down the chimney?

I don't know, but suspect the chances pretty low.

What could one do to lessen worries? Use an insulated air intake duct, perhaps. Build some kind of metal cover/shield over it as it passes through the wood storage box.

Or how about venting the combustion air intake duct to the crawlspace--if crawlspace is ventilated. Or run the air intake under the floor, through the crawlspace to exterior vent. That way you could avoid the woodstorage box entirely.

Just some thoughts of a consumer searching for a woodburning hearth.

BTB

 

[karl]

Btb,

You make some very good points. I thought about a flapper of some sort to ensure I never have a reverse draft or a double wall intake and then a 6" metal spacer to get my clearances like a chimney. But before I go to all that trouble I'll just stop using the pass through. As for venting from the crawl space. There isn't one. I have a basement and right below this fireplace sets another fireplace. The block goes from the basement to the roof.

Now, let me tell you about the third stove store I visited today. Elk's going to love this.

I asked about outside combustion and the guy said they usually just leave the top of the chimney uncovered so the stove can draw air in from there. Which by the way, answered the next question I was going to ask him. Do you install a block off plate where the damper used to be? Would some one please tell me why I should buy a stove locally and not off of the internet? I don't care to pay a little more. I'd rather not install the thing myself, but look at what I'm dealing with. I bet these guys would install an insert in the back window of my truck if I asked them to.

 

[BrotherBart]

Yeah, that is scary. But I do have to ask why you are set on having an outside air source. Is your house that airtight so as to cause a problem with combustion air? I ask this because the only other reason would be drafts caused by the draw of the stove. With an insert the blower is going to be causing a heck of a lot more draft pulling cool air back to the stove than the intake air ever will.

Saves a lot of engineering just to knock that 4" plug out of the side of the Summit insert and let it do its thing.

 

[builderbob]

Btb,

Now, let me tell you about the third stove store I visited today. Elk's going to love this.

I asked about outside combustion and the guy said they usually just leave the top of the chimney uncovered so the stove can draw air in from there. Which by the way, answered the next question I was going to ask him. Do you install a block off plate where the damper used to be? Would some one please tell me why I should buy a stove locally and not off of the internet? I don't care to pay a little more. I'd rather not install the thing myself, but look at what I'm dealing with. I bet these guys would install an insert in the back window of my truck if I asked them to.

After my travels so far to seven different fireplace stores, I too have had mixed results. I have hit some stores where the answers were credible, and educational. But out of seven shops, I hit more than one where the answers were *scary*. I will say that at those places, I was not talking with the owners or even installers, but with salespeople.

But still, it does give one pause on just who do I want to deal with, and if "local" is always such a good idea.

The hearth industry and *credibility*---an interesting subject.

BTB

 

[BrotherBart]

But still, it does give one pause on just who do I want to deal with, and if "local" is always such a good idea.

The hearth industry and *credibility*---an interesting subject.

BTB

I can't wait until you have to pick out the roofing and the carpet! ;-)

 

[webbie]

Hey, in WV a 50% "good store" rate would be a high number! When I lived there, I had a friend who burnt down his house while trying to freshen up his kitchen cookstove with a gas can. The can lit on fire, and he tossed it away across the living room - house was a total loss!

But in terms of the outside air, my suggestion would be NOT to use it except in the tightest of houses. Many in the industry have also questioned their use, including John Gulland, an expert in these matters. Things may be different with open fireplaces or pellet stoves, both of which use vast quantities of air compared to a sealed wood stove.

 

[builderbob]

Those choices were taken care of long ago. A wrong choice there doesn't necessarily kill you.

BTB

 

[builderbob]

But in terms of the outside air, my suggestion would be NOT to use it except in the tightest of houses. Many in the industry have also questioned their use, including John Gulland, an expert in these matters. Things may be different with open fireplaces or pellet stoves, both of which use vast quantities of air compared to a sealed wood stove.

But then again Tom Oyen (I think that's his name), runs the Chimneysweep stove shop in Bellingham, Washington, has directly and point by point refuted John Gullands article against outside air.

Tom's website has his point by point rebuttal posted---some prior thread there was a link to it.

BTB

 

[builderbob]

But then again Tom Oyen (I think that's his name), runs the Chimneysweep stove shop in Bellingham, Washington, has directly and point by point refuted John Gullands article against outside air.

Tom's website has his point by point rebuttal posted---some prior thread there was a link to it.

BTB

Here's the link---and from Tom's site he links to John's article against outside air at Woodheat.org. Tom gives you BOTH sides of the story. I found him very convincing.

(broken link removed to http://www.chimneysweeponline.com/hooa3.htm)

BTB

 

[karl]

Craig,

It's nice to see that you have escaped from this state with all of your fingers and toes. I love it here and most everyone is hard working and friendly, but Robert Byrd sure hasn't gotten enough brain appropriations to go around yet. If you guys think stove installs are scary around here, take a look at what passes for automobile repair shops. Reminds me of the old joke.

Why can't the police solve a murder in West Virginia?

There are no dental records and all the DNA's the same.

 

[Gooserider]

I would think that insulating the duct even slightly would probably give enough margin, and still let you use the pass through. I don't think it is likely you'd be backdrafting, and that's the only time you'd ever have a problem. Another possible approach, though it might not help a whole lot in regards to the combustibles issue, is what about flipping that "L" duct over 90* and going out the back of the fireplace, through the closet, and out the side of the wall? Probably still need the same level of insulation on the duct to avoid combustibles, but the question is where is the space more valuable, in the wood passthrough or the closet?

Gooserider