Furnace flue connection, which is better...straigt out, or up, then out.

[DMoore]

I'm installing a Brunco wood furnace. The flue comes out the back of the stove. I'm also installing a Metalbestos chimney up the side of the house. Is it better to have the stove pipe come straight out the back of the furnace and through the wall, or come out of the stove with a 90, up a few feet, another 90, and then out through the wall? I would be eliminating 2 90's with the first method, so I thought I would get a little better draft. With the latter method, I may be out of luck if I ever got a different stove and the flue did not match up with the original. Any downside to putting the 90s in before I go out throught the wall?

 

[Henz]

less bends the better

 

[begreen]

You want a good, uphill pitch to the pipe in any horiz run and you want to keep the horz. run as short as possible. Consider using 2- 45s instead of the 90's to assist draft and eliminate the horiz. run.

 

[trailblaze]

when getting bids to install my chimney.... the more bends the more $$$ it came too... plus everyone told me straight up leads to better draft

 

[DMoore]

If I do go straigt out the back of the stove and through the wall to the main stack, I will be looking at a 48" horizontal run to the main stack.

 

[begreen]

What would be the pitch of the run? In other words what is the height of the furnace exit collar and what is the height of the thimble? The other thing to consider is which alignment of the furnace works best with the trunk duct it is connecting to?

Moving to the boiler room for more targeted responses.

 

[DMoore]

The flue collar is right about 4'. The height of the thimble is what I'm trying to decide on. If I come straight out of the flue collar and through the wall, I will have about a 4' horizontal run to the the T of the stack. I could have a 90 at the collar, go up a couple of feet, then a 90, and straight through the wall to the T. This way would give me the most versital set up down the road if I should get a different furnace. I've head that it is better to get some vertical run asap, then I have heard the opposite. The dealer said it really wouldn't make much difference.

 

[BrownianHeatingTech]

The flue collar is right about 4'. The height of the thimble is what I'm trying to decide on. If I come straight out of the flue collar and through the wall, I will have about a 4' horizontal run to the the T of the stack. I could have a 90 at the collar, go up a couple of feet, then a 90, and straight through the wall to the T. This way would give me the most versital set up down the road if I should get a different furnace. I've head that it is better to get some vertical run asap, then I have heard the opposite. The dealer said it really wouldn't make much difference.

Two 90's like that should not be an issue, unless the chimney is very poor on draft. And, as you said, it will be more flexible in the future, if you decide to install a different piece of equipment with a higher flue outlet.

Much as "straighter is better," you're not talking about any sort of crazy length of pipe or number of bends. The added benefit of future flexibility should control here, and dictate a chimney breach at a reasonable height.

Also, consider installing a tee instead of the first 90 (at the appliance), for ease of cleaning. You'll still want to pull the pipe on occasion, but intermediate cleanings can involve just opening the tee's plug and sucking out the ash. Making cleaning easy will encourage it to actually get done, in the long run...

Joe

 

[mtfallsmikey]

1/2" per ft. would be a good grade if you can get it...