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Moving furnace vent

13K views 15 replies 6 participants last post by  hvaclover 
#1 · (Edited)
I've got a 78% efficient Lennox g20 up flow gas furnace in my basement venting through 4" B vent run out my old chimney flue. It spans three stories. I'd love to install a wood stove on the main floor and the "most practical" way to do this is use a flex liner in the old flue.

The problem is there is not enough room for both the b vent and the wood stove flex. Thus if i want to even consider a wood stove in that location i need to move said vent (or go high efficiency which i'd rather not right now).

My question is: Can i side vent the furnace as long as it is up and 1/4 over a foot rise and install an a secondary blower that switches on and off with the furnace such as something by tjerland?
 
#6 ·
I also have a Lennox G20 where my 4" pipe is venting out of an existing chimney. I moved the furnace so I would like to vent it out of the side of the house instead. If I were to keep this furnace for now, would there be an issue with side venting it? It would be away from windows, and sufficiently high off the ground.
 
#8 ·
Its allowed to be side vented, if you use a power venter(tjern).
The power venter must have a proving switch.
You must also install a barometric damper, and need to set up the proper draft. Which will require a manometer.
 
#9 ·
Been I am not sure but I know around here the only way an 80% gets vented out the side is if it's was on the recall list of plex pipe.

They will not allow (to the best of my knowledge) any type of gas fired appliance to be side wall vented unless the smoke pipe is stainless steel along with the power venter.

Makes it a pretty expensive alteration.
 
#10 ·
Thank you both for your input. I was able to get a copy of the Installation Instructions for this furnace from Lennox and here was the text about Horizontal Venting:

"This furnace is design certified by the American Gas Association for horizontal venting through an outside wall only with the use of a Field Controls Company Model #SWG-5L side wall venting kit available from Lennox Dealer Service Center. No other Field brand venting kit or any other manufacturer’s venting kit is acceptable. Horizontal venting of this furnace without the use of the above stated kit is prohibited."

FYI - I contacted Field Controls and they've since replaced the SWG-5L with the SWG-5G.
 
#12 ·
Thats just your local code people not knowing how much safer a side wall power vented unit is over one that is vented in the chimney with a water heater.
 
#14 ·
I'll stay out of the code argument :) But, in my case, when we bought the house a couple months ago the furnace location originally caused the vent pipe to run laterally about 5 feet before turning 90 degrees around a wall and running another 6 feet to the chimney. I wasn't pleased with the furnace location, or the length of the vent pipe, so I moved the furnace to a more ideal out of the way location a bit closer to the chimney. However, the chimney is in disrepair, there are signs of moisture problems, and the furnace is still farther from the chimney than I am comfortable with; so I would like to abandon it and run the water heater through the back of the house as well. It seems like running it through a side wall is our best option. I'm just now trying to find the most ideal location to be out of sight, and a sufficient distance from all the windows. Thanks again for your input.
 
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