Yet another OAK question, 25 PDVC

[Dustin]

After much searching and reading here, I'm deffinetley going going to install an OAK.

Problem, the stove is on an interior wall, vented with 6 inch SS liner inside a masonry chimney for 25 feet.

Some is the reading I have done says, don't pull outside air from the crawl space. Is this an accurate statement?

To get to an outside wall, I'll need to somehow get the pipe through the floor, through the crawl space and out. My manual says I need to use 4 inch pipe for this.

Dumb question, can I run three inch for a foot or so out the back or the stove through the floor, then increase to 4? Also, how is that connection made?

Any and all input welcome

 

[Bioburner]

The reasoning for the need of 4 inch is to lessen the friction loss because of the length. I can't see any reason to not use a couple feet of 3" at the stove. Need to know what you will be trying to use as a intake piping to give any further idea as to adapter. Maybe Mike will chime in with his factory advise.

 

[Dustin]

I'm thinking 4 inch dryer vent

With maybe a couple feet of 3 inch stainless flex? Auto parts store I assume for that stuff?

 

[Bioburner]

3 inch is also available in dryer venting but better is the flex exhaust pipe as could take a bit more of a beating and good clamping to stove.

 

[Dustin]

You guys have much better sealed houses than us so we draw from the crawl and ceiling space all the time.
Maybe I am missing something but if your crawl space has outside ventilation then why not draw from there?
The restricting factor of air movement is pushing out the dirty exhaust, not the incoming clean air. The intake pipe can be far smaller than 3" (we routinely run 2" over 2') so 3" is heaps.
Why dont you draw down the chimney liner like mentioned by others? Harvest some of that wasted flue heat.

As I sit here and stare at where the stove is going, I'm wondering about the chimney or crawl space. My chimney is lined with a 6 in SS liner in a fairly large flue. I do have a concern however of pulling CO back into the living space should my liner ever develop a problem. With the strong draft the liner has now (was Hooked to wood) if it ever developed a hole it would suck air rather then pull air. My thought is if I stuffed the OAK hose inside that void, it may reverse that at some point. Also having a warm flu pipe is nice for a natural draft.

The crawl space is another story. My house is old, 1955 with cinder block foundation. Despite my best wintertime efforts to seal
It off, I know it's still leaky.

Can anyone think of a contraindication to just using the crawl space air in an old house? I wonder if pulling the cold air in would cause the floors to be warmer, or cause pipes to freeze faster?

The only reason I'm thinking this route,
Is, if I run this to an outside wall, it's
going to be a long, tricky run as the stove is dead center in the middle of the house.

I guess another option is to run an oak pipe the entire chimney length and terminate it at the cap? That's about 25 feet..

If anyone has used their crawl space air without negative effects please chime in...

 

[alternativeheat]

Re the chimney; You are not going to drag CO back into the house as it is only going into the fire at worst. THe fire won't run long if it is dragging smoke back in and will just go out. We see it often where horizontal flue systems are incorrectly installed.
THe OAK wont pull much heat from you flue. You are complicating a simple solution, dont bother running an OAK up the chimney, just use the chimney.
If your crawl space is not air tight then it is fine but I would recommend the chimney option every time.

I agree, the flue is the simple and most efficient solution wrapped up in one. I also agree, if you get a pin hole leak in your liner ( unlikely but still if) then the intake air of the stove will just suck it back into the fire chamber not into your house. In fact less likely than just leaving the leak into the flue, which has the potential to seep into the house with the top capped off and it's a central chimney in the house ( goes through the house not an outside wall). But yes a vented attic or crawl space works too if it makes the OP feel better. And if he feels it's not vented enough put in a small vent.

 

[Dustin]

Got it, thanks for the info guys!

So, how far up past the first flue tile do I need to go? I have an insulated block-off plate currently in place. Do I need to add some air holes in the masonry chimney somewhere? Its sealed pretty tight up top, plate, silicone and cap