Worst-Case Depressurization Test

[jonwright]

*snip*

Not to many of us from Missouri on this forum. Which I find interesting since we are surrounded by thousands of acres of excellent firewood. I guess natural gas is so cheap and wood stoves are so expensive that most don't think about wood.

Probably because it's still like in the 60's during the day right now - folks in the NE and mountains already have had snow. Realistically I've fired up my stoves not because I NEED to because it's cold - but because I just want to.

 

[jonwright]

*snip*

The OAK for the Cumberland Gap uses a 4-inch flex pipe. Since the stove is in my basement and it will run up the concrete wall to vent through the rim joist, I would like to try and hide it in the finished wall (which will be metal stud, unfaced fiberglass batts or rockwool insulation, covered with cement board and stone). Since the metal studs are ~3 5/8 inches, could I reduce to a 3 inch pipe to hide this inside the wall or would it be too restrictive? I could also pull the wall out from the concrete 1/2"-1" when I install, but would prefer not to do that. My dealer says that 3 inch would probably be OK, or I could "oval" the flex pipe within the stud bay, but thought it better to get another opinion.

Personally, I'd just crush down the 4in-flex pipe to fit between the studs. Simpler, you won't have to mess with joints and the area/volume of the pipe will be close as if it's round. Might have some effect of the ability of the pipe to move volume of air, but not as restrictive as 3 in I think. Need to also be sure you are OK with distance and the diameter of the intake. Longer the distance the larger diameter you'll need. 4 in probably won't work for a 30' run!

Need to be cautious since much of the flex pipe I've used is spiral - if you crush or mess with it too much it will come apart and leak a little. Nothing some caulk or mastic tape can't cure, I think.

Don't forget to have it high/sheltered so that snow or something else won't cover it up.

 

[kmachn]

The OAK will be coming through the rim joist right around the area for the walkout basement, which happens to be beneath a covered deck. So snow, grass clippings, etc, won't be an issue, and will only be about 8' high. I am generally not comfortable using the flex pipe in pretty much any situation, which is why I would rather go with 3 inch solid. But you're right, crushing it down to oval is probably a better choice, being less restrictive. The chimney is pretty long so my thought is that there would be a good draft either way. Has anyone tried their own oak on an EPA stove and been successful with a 3-inch? If no other thoughts, I'll squeeze the 4-inch flex

 

[jonwright]

Flex will be fine. It's used all the time for intakes. You will want to be sure your length is OK for the diameter. Maybe a call to Qfire would work. Are you running this beyond the recommended distance? I know for the FPX for sure there were guidelines for duct diameters if lengths were going to be beyond the manual. Travis tech rep said they'd have the engineers cruch the numbers for me if I needed to (I was indeed going past their recommendations for duct length).

 

[kmachn]

Flex will be fine. It's used all the time for intakes. You will want to be sure your length is OK for the diameter. Maybe a call to Qfire would work. Are you running this beyond the recommended distance? I know for the FPX for sure there were guidelines for duct diameters if lengths were going to be beyond the manual. Travis tech rep said they'd have the engineers cruch the numbers for me if I needed to (I was indeed going past their recommendations for duct length).

Ya know I have the OAK at home, opened up the box but have done little since. I'm trying to finish a project before I put up that metal stud wall and officially install the OAK, so I haven't looked at the installation manual yet.

I just had another thought, though. I may be able to check an HVAC parts store (Home Depot, Lowe's or online) and use some 3.25" x 10" or something similar in the wall cavity. I would just need a 90-degree boot to a 4-inch round to connect them. That would give me a whole lot more sq inches through that 7.5' run.
Thanks for the thought on that diameter, I'll definitely check the manual and see what the max length is before having to upsize. The dealer told me it should be fine, but he did hesitate so I don't think he was going off of a specific guideline from QuadraFire.