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Pitch11 09-23-2008 01:41 PM

Moving furnace vent
 
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?

Termite 09-23-2008 01:47 PM

Not to my knowledge. The b-vent must terminate no less than 2' above any vertical surfaces, and proximity to windows and doors is an issue as well.

Termite 09-23-2008 01:47 PM

If you're running a 78% furnace, switching to a high efficiency unit would probably pay for itself in no time at all.

Pitch11 09-23-2008 01:50 PM

that would defeat the wood stove all winter route...

Also i fixed the link above.

dac122 09-23-2008 02:20 PM

If you've not purchased a wood stove, go for a pellet model. They are so efficient these days you can side vent them. The btu cost is comparable or less than wood.

idec25 10-23-2008 01:58 PM

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.

hvaclover 10-23-2008 03:24 PM

Itis not rated for side wall venting, Nope. No way.

beenthere 10-23-2008 10:49 PM

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.

hvaclover 10-24-2008 09:00 AM

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.

idec25 10-24-2008 09:47 AM

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.

hvaclover 10-24-2008 10:15 AM

Just checked our local code. It's permissible, how ever the restiction are so strict it makes almost impossible.

beenthere 10-24-2008 03:08 PM

Quote:

Originally Posted by hvaclover (Post 176204)
Just checked our local code. It's permissible, how ever the restiction are so strict it makes almost impossible.

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.

hvaclover 10-24-2008 03:23 PM

Quote:

Originally Posted by beenthere (Post 176370)
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.


Hey now, we got one of the best Mechanical departments in the country.

We just dont want those ugly ass terminations poking out the side walls.

Ok for 90% but not 80%s.

idec25 10-24-2008 03:40 PM

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.

beenthere 10-24-2008 04:03 PM

Just keep in mind.
That power venters are not always quiet.


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