95% AFUE furnance venting

rcouretMay 23, 2009

Most articles and post here said you vent a 95% AFUE furnance out the side of the house with PVC. Is that a requirement or can you vent thru the existing roof jack.

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veesubotee

Don't know what a 'jack' is, but 95ers are vented through the roof all of the time, as long as length/elbow/diameter restrictions are not exceeded.

V

    Bookmark   May 23, 2009 at 10:57AM
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rcouret

"roof jack" just what some of us old boys called a Roof Cap/Vent.

Thanks, and I assume the PVC is to prevent corrosion problem associated with the moisture in
the 95% furnance?

    Bookmark   May 23, 2009 at 12:14PM
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veesubotee

Does your 'jack' looks anything like these: http://images.google.com/images?hl=en&q=roof+cap&btnG=Search+Images&gbv=2 ?

I can't comment on your local codes. My impression is that it would be prohibited, due to close proximity of the intake and exhaust stacks. Bad news.

Are you not able to do any sidewall penetrations, or are you afraid of additional roof penetrations?

V

    Bookmark   May 24, 2009 at 7:55AM
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baldloonie

You can use existing vertical vents as a chase but the vent & intake must be appropriate size PVC all the way outside.

    Bookmark   May 24, 2009 at 10:03PM
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rcouret

thanks for info. Have since found manual for 95% furnace on web showing vent and intake.
I will use outside wall for intake and existing roof vent for venting.

Yes, and another example of roof jack...
http://www.pricegrabber.com/vent+roof+jack/products.html/form_keyword=vent%20roof%20jack/skd=1/mode=pg_yahoo_us_adv

    Bookmark   May 25, 2009 at 9:40AM
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veesubotee

"thanks for info. Have since found manual for 95% furnace on web showing vent and intake.
I will use outside wall for intake and existing roof vent for venting."

This can cause problems (heat shutting down) and may be prohibited by code.

Check your manual and see if it says anything about intake and exhaust pipes being in the same pressure zone.

V

    Bookmark   May 25, 2009 at 2:06PM
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veesubotee

P.S., you can have a concentric (1 opening) termination in the sidewall. This serves intake and exhaust.

V

    Bookmark   May 25, 2009 at 2:10PM
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rcouret

V
"intake and exhaust pipes being in the same pressure zone."
You got to explain that to me. I can understand the difference in pressure and a zone areas. You got a zone on different floors,attic, outside, etc. If we call the vent as an outside Zone what zone do I draw from... if specs require?
I will check that out. I suspect the contractor should know but would like to be armed with as much info as possible when work is in starts/progress.

And I see no problem in having a concentric opening, but isn't that the same zone? and even closer.

bob

    Bookmark   May 25, 2009 at 8:07PM
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zl700

In simple terms, many cat 4 vented appliances require intake and exhaust in close proximity of each other with similar lengths and elbows when installing as a direct vent otherwise the furnace pressure switches do funny things and the furnace usually doesn't work well.

Manual will state install requirements

    Bookmark   May 25, 2009 at 10:29PM
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rasinc35

We are getting a Lennox G71P installed. I am used to flues going trough the roof. The salesman said it would be vented through the wall. Is that good? What if it gets blocked by snow?

    Bookmark   May 27, 2009 at 5:33PM
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va6strings

I got a bid on a system that included the Lennox G71P, and they said it needs to be vented via PVC because the unit draws so much heat out of the air that the remaining air is too moist for metal ducts. He recommends the concentric vents thru the wall for these units b/c it helps to balance airflow in and out, though some people install them with only outbound PVC, which he doesn't like because it can cause vaccuum situations in the house. I'm just attempting to repeat what I heard from a NATE-certified Lennox installer. Good luck to both of us finding the right equip and installer!

    Bookmark   May 30, 2009 at 12:37AM
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