High Efficiency Furnace intake pipe does not go outside. Is that OK?

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Not really claiming especially low bills here, but in my local climate which is in upstate NY this is a rather typical situation.
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My 1957-built home in the Chicago suburbs still has the original Lennox for ced air funace. It has a real chimney for the exhaust, and drew heated bas ement air for the input.
About 20 years ago I put in a 4" dryer duct type of air input from the outs ide to a 4" hole I cut in the side panel of the furnace. It is pretty much sealed off on the other sides, so now the outside air is probably 90% of t he combustion air the furnace uses. I also filled in the gas nozzle orific e and then drilled it back out at about 1/2 the cross section area, so that the flame in the furnace is much smaller (about 50%). That reduced the he at available, but I had previously checked and the furnace never had to run full-time even at below zero temperatures, so I felt comfortable in making the change. I did have to rebalance the air-gas mixture shutter to get a clean blue flame, but it was well within the adjustmment range provided. G as consumption is down noticably without any change in comfort level, and t he slight drafts we used to get around the weatherstripped doors to the out side has been elminated.
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On 2/17/2015 4:07 PM, snipped-for-privacy@sbcglobal.net wrote:

ed basement air for the input.

y much sealed off on the other sides, so now the outside air is probably 90% of the combustion air the furnace uses. I also filled in the gas noz zle orifice and then drilled it back out at about 1/2 the cross section a rea, so that the flame in the furnace is much smaller (about 50%). That reduced the heat available, but I had previously checked and the furnace never had to run full-time even at below zero temperatures, so I felt com fortable in making the change. I did have to rebalance the air-gas mixtu re shutter to get a clean blue flame, but it was well within the adjustmm ent range provided. Gas consumption is down noticably without any change in comfort level, and the slight drafts we used to get around the weathe rstripped doors to the outside has been elminated. Lengthening the burner cycle by down-sizing the orifice probably helped a lot. On newer furnaces, the heat exchangers have a very narrow efficiency band, which is much more inefficient on either side of the peak heat transfer BTU input. If you downsized the orifice on one of these furnaces, I would doubt anywhere near as much of a benefit in operating cost, since then your longer longer burner cycle would occur at a far less efficient operating point for either the burner or especially the heat exchanger. Your method worked great for older furnaces, which also were notoriously over sized.
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department. My furnace is a dual stage, and I've locked it down to the low output. Smallest furnace I could buy, other than a "trailer" unit, and it has never run more than 9 hours in a 24 hour period - so it is still oversized.
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Mine is also oversized, running about 65% of the time for the fan and maybe 50% of the time for the burner in -5 degree F outdoor temperature. Original house has a 160K BTU/hr furnace (circa 1952). I replaced it with a 75K and subsequently updated windows, doors, insulation. A 50K unit would suffice albeit marginally at these unusually low outdoor temperatures.
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wrote:

input 80%+ unit strapped down to 3500 (about 29000BTU out) Monday was the coldest day we have had in 200 years and the furnace ran less than 9 hours. (-36C, and windy)
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Remarkable ! Impressively low consumption and boy you sure get LOW temperatures !
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On 2/17/2015 8:35 PM, Smarty wrote:

A lot of homes, older ones, are also over sized. When I did HVAC install, we almost always put in smaller than what we took out. One man did insist on a larger one, boss did his best to reason with him, but it wasn't working.
As for myself, I took out a 80k and put in 70k, this being in 1994. Still over sized.
- . Christopher A. Young learn more about Jesus . www.lds.org . .
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On Wed, 18 Feb 2015 07:48:00 -0500, Stormin Mormon

lot less insulation.
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On Friday, March 3, 2006 at 9:43:43 AM UTC-5, snipped-for-privacy@yahoo.com wrote:

furnace makers moved to outside air because it can be cleaner, inside air can have things like chlorine bleach in it, that led to early corrosion and heat exchanger failures.
tis from a HVAC buddy of mine who taught it for 25 years.
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