Fresh air ducting

[n2brk]

Hello -

I am writing because I am pretty frustrated, lol. I am trying to make a fresh air duct to my wood stove fireplace insert. The insert has a knockout panel on the side and an adapter to let me run a 5" flex pipe to the great outdoors.

Since it is an insert, it is inside my fireplace and there's a shroud that covers the rest of the fireplace opening around it; large fireplace/medium insert.

I need to run the 5" through the ash pit in the fireplace that exits at the basement floor about 8' below... then I need to run it out the ash pit cleanout door, and up 8' and over to the outside wall of the house. The problems that I'm seeing are two: First, do I need to knock up some tin to do this, or can some insulated flex duct handle the heat in there? I have the excess area of the fireplace packed around the stove with Rocksol insulation, so it should be cooler for the flex but not too cool! Secondly, that's a loooooooottttt of length... is it too long?

I am tempted to just let it draw air from the basement, but my home heater is right there and it draws from the basement already, so in the event that they are running at the same time, the furnace (185,000btu) will suck a lot of air from a couple feet away, and that can't be good.

SO in the spirit of making mountains from mole-hills... do I create something to go from the outlet of the stove to the clean out, or do I use flex duct? Do I run it all the way outside or just to the basement... in which case I should run the heater to the outside. So much to think about, lol.

What does the collective think?

Thanks!
Wally

 

[begreen]

Greetings. Would it be possible to poke a hole in the brick at ceiling level in the basement to open up a hole into the ash dump chute? That way you could put a ninety elbow in and head directly to the outdoor wall, all at ceiling level. Usually this piping is 4". What insert is this?

 

[n2brk]

I had thought about that, and I suppose I could... but would I need to reinforce the cinderblock wall where I punched the hole? Or maybe I could do it with a heavy walled pipe that would be strong enough not to need to. Hmm.

Drolet 1400.

Thanks!

 

[begreen]

No, I don't think you will need to support anything if this is a wide, cement block base with a chase down it for the cleanout, but post a picture of the area just to be sure.

 

[n2brk]

that's exactly what it is; typical cinderblock wall.

 

[begreen]

I would guess that if you don't swiss cheese the wall with a lot of holes it will be fine. A single hole is not going to affect it's integrity.

 

[n2brk]

ok, that's no sweat. Any thoughts about the stove end of things?

Thanks!

 

[begreen]

What insert?

 

[n2brk]

Drolet 1400.

Thanks!

 

[begreen]

My copy of that manual must be old. It doesn't seem to say anything about an outside air connection.

 

[n2brk]

http://www.drolet.ca/upload/documents/manuels/45221A_16-01-2013.pdf

page 15 shows the fresh air kit.

 

[begreen]

Yup, they definitely have updated the manual, thanks. That OAK looks like a real pain in the butt, especially if you are trying to reach a cleanout behind the insert. 4" flex needs enough room to turn a corner. The rect to oval adapter is the issue. If it was round you could mount an elbow to it.

 

[n2brk]

right and it's 5" so it's even worse! That's why I was thinking about trying to knock up something out of tin that would give me a box rather than just the oval nipple, and then I could put a flex pipe into that straight in instead of making a turn. Honestly, I can't see a 5" flex having the room to make the turn otherwise; the fireplace wall is close.

PITA, eh? lol

Thanks for hanging in with me.

 

[begreen]

I am following you. With a box on the side you could go direct with a takeoff collar on the box end. Plan on 4" flex. That will be sufficient and will afford standard sizing.

 

[n2brk]

cool. 5" is harder to find and of course in this case bigger is bigger PITA fit-wise. So I am glad to hear 4" will suffice.

 

[begreen]

An alternative might be to terminate the fresh air supply at the ash cleanout with a flush plate. Remove the rect. knockout on the stove and seal the surround edge to the fireplace wall with silicone. Regardless of approach, be sure to have a rodent blocking screen on the outside air intake.

 

[n2brk]

that's kinda cool. I suppose I could pack Rocksol insulation to keep all of that cold air from making it to the house when the stove is off. Hmm... you may have just simplified the hell out of this

 

[DBoon]

It sounds like you are on the right path - get it to the outside with the minimum run and the fewest elbows.

I have a similar setup, and I just ran the fresh air intake into the basement. I avoided running the wood stove in a startup fire mode while the oil boiler was running or could be running. If I didn't, I would get slower and smokier startups due to a worse draw. Once the fire was up to temperature and stable, the oil boiler didn't seem to affect it much. I also had deliberately left some pretty significant air gaps in my outdoor basement door to let plenty of fresh air in for both units, just in case. Note that my oil boiler was half the size of your furnace.

This summer, I replaced my old oil boiler with a unit that draws intake air from the outside, and I expect fewer issues with this. Perhaps your furnace can be retrofit for outside air intake? That might be an easier retrofit than doing the OAK to the outside on the Drolet.

 

[n2brk]

my furnace has a 4" pipe that comes up and hits an elbow and just stops. It sucks air right out of the basement. I could very easily route that outdoors.

 

[n2brk]

Oh man. Two years have gone by and I guess I didn't remember it being so tight side to side!

 

[n2brk]

No room for duct, whether 4" or less. It looks like the open trap caulk facia method is going to be the only way to go.

 

[n2brk]

sorry, my phone seems to have flipped everything here, even though it isn't on the phone, lol

 

[n2brk]

I got in there yesterday and finished up the conversion.

First, I popped the knockout to open her up to receiving make up air. Then I noticed that there were huge gaps allowing the make up air to mix it up with the blower air that distributes the heat - that CAN'T be good! So, I used some stove cement make a barrier. Then I used some pieces of scrap metal to create a "duct" from the cleanout to the knock out, and packed my Roxul back in around everything. I added piece of scrap to the front to let me insulate before putting the decorative facia back on. I went into the basement and opened the ash pit door. There should be a new supply of basement make-up air now, and no leakage of that air to the heated air coming from the unit and squirrel cage blower... as well as no mixing of room air.

I suppose that when I'm not running the stove I should shut the ash pit door in the basement? Will it create a draft from basement air up through the chimney? I think fully closed on my damper still permits some flow; a low setting not an "off".

I also rewired my thermostat so that when I click the fan on, it is turning on the slow speed fan circuit instead of my A/C high speed fan circuit.

I think that makes me about ready for winter. Now I need more firewood!!

Thanks for all of the help!

Wally