New Harman Absolute 43 venting question.

[ColoradoSolar]

The house I just bought has an older Avalon Astoria in the living room that I am going to replace with a Harman Absolute 43.

The current vent goes through the wall about 23" from the floor and then "outside" it does a 90 and goes up through the roof. The "outside" is in sort of a metal chase (about 2'x3') on the outside of the house. With the Harman exhaust being about 8" off the floor I am looking at having to put a 90 out of the stove and then another 90 to go through the wall, with the existing 90 outside that puts me at 15' EVL which according to the Harman manual is the total vent length I can have at 7800' elevation. But the problem is there is another 12' or so of vertical venting that goes up through the roof. I can't go horizontal because the vent comes out in the middle of the porch. Will the extra 12' (6' EVL) make a big difference or can I just let slide?

Thanks

 

[Lake Girl]

What size venting is existing? The exhaust outlet on the Astoria is 4".

Edit: Just pulled up the manual for the Absolute ... max 20 EVL for 3" with 4' maximum horizontal length.
http://downloads.hearthnhome.com/installManuals/Absolute43_I.pdf page 16
The general rule of thumb is 15 EVL for 3" but manufacturer's manual takes precedence.

Just found the 15 EVL in reference to your location elevation...

 

[ColoradoSolar]

There is currently 4" pipe installed.

I agree in going with the manufacturer's recommendations but I'm not sure how I am going to shorten the run.

 

[Lake Girl]

You might want to contact your Harman dealer with the question. The max EVL for 4" is 30 w/o factoring in geographic elevation. The second chart really doesn't address vent size at altitude (3" vs 4").

There is a high altitude fan blade available from Harman. Might want to ask the question about that.

Edit: Is it possible that two 45 elbows can be used to hook up the exhaust to achieve the height required at the wall? Possible to adjust the thimble lower to reduce need for elbows inside?

Edit: Is it possible to elevate height of the hearth the stove is on?

 

[ColoradoSolar]

I don't think I can use 45 elbows because that would push the stove too far into the room. Can't move the thimble without cutting a new hole in the wall, which I really don't want to do.

I had thought about raising the hearth and I could probably do that, I would just have to figure out a way to do it that looks good.

 

[Mt Bob]

I think with the high alt. impeller and 4" it would be fine,but this is a new stove design,best to talk to a harman repair person.Also,pipe does not have to go to roof.This number-14062729850,is where i get parts,and they have an excellent service person,you could call them.They are a harman dealer.

 

[ColoradoSolar]

Also,pipe does not have to go to roof.

Where the current stove vents through the wall I have to go up through the roof because it is in the middle of a patio with a large roof overhang.

 

[Lake Girl]

Would check with the dealer about the high altitude exhaust fan blade ... may not need to do anything other than change the type of blade used.

 

[ColoradoSolar]

I will do that.