Intake duct size: Travis FPX 44

[jonwright]

So I’m finishing up the install on my FPX 44. We had the blower (intake) unit mounted under the house, and I want the duct to run to the outside. Problem is, it’s about a 28’ run. I made an adapter to go over the front of the blower/intake box to adapt 9†pipe. Book says max 15’ run for 6†pipe, 25’ run for 8†pipe. So I just went with 9â€.

The chimney pipe is cooled pipe and the intakes/pipe are 7â€

So my question is this: If I’m running 9†for the intake, and choke it down to 7†for a roughly 8' run right at termination to the outdoors for a groovy intake that came with the chimney cooling vents (I don’t have to use those so I have them left over) am I choking down the CFM needed? I mean, really?

I’d almost rather like to use the 7†intake/vent that came with the stove (this WILL NOT be seen as it will be under my deck) because it’s a bit smaller and already set with a rain guard and screen on it.

The anal-retentive side in me wants to run the 9†duct all the way through the wall, but I"m concerned with putting a hole that big in my concrete block. Plus at this point I've been nickel and dimed with building my house and I'm not interested in getting a custom 9" intake made unless I need to. Plus 9" aluminum flex duct I'd have to do a bit of searching to find.

Am I thinking too much? I'm just going to have a go with the 7" anyway, but wanted to see if I'm going to be disappointed and need to swap it out anyway.

I'm heating a 4,100 square foot house and the unit is in a room with 25' ceilings, so I'm going to need all the CFM I can get.

 

[Trail_Time]

You need to use both. The stove will have 3 intakes in all. Two supplied 7" ducts that go into the top of the unit at the rear are for the air cooled chimney but are also used to cool the outer shell which makes it zero clearance. IMO for a 28' blower run you will want all the volume you can get. I only have about a 2' run and would like to see more air movement when trying to warm up from a cold house.

 

[Shane]

You'll need to go with the bigger pipe for sure. The resistance of that long a run will require the larger pipe.

 

[jonwright]

Yeah, I used 9" all the way down, until the last few feet. I used the 7".

Since I'm running my duct in the crawlspace we just put the 2 cooling ducts behind the vent screens in the block wall and I sealed around them. Since all this terminates under a covered deck there's very slim chance of water blowing in. So I have the 2 7" intake hoods left over.

So for the majority of the intake run I used the 9, then for the last 6-8 feet or so I used the 7" alum flex duct then the hood to penetrate the block since I don't have enough vent holes in the block for the intake.

I've completed the work, and I *THINK* maybe I can tell a bit of difference in air flow vs. when there was NO duct hooked up to the blower, but the incoming air smelled like dirt since it was coming from under the house. But then again I only ran the stove once so I'm not really sure about how much it blew with no duct.

So really I'm just wondering about theory - Guess if I wanted to know bad enough I could disconnect some of the duct, but that's rather a pain about now.

But if someone can for sure tell me it's a bad idea and worth redoing the last few feet I'll do it. I'm just not sure at the moment.