making gas furnace more efficient trick?

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You think some internet legend is smarter than the engineers who design furnaces? Not likely.
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Don't go fiddling with your furnace. If you want it at maximum efficiency have a pro come in and clean the unit. Make sure that there is enough fresh air coming into the furnace area for good combustion and for air flow up the chimney.
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This sounds like BS to me, although I do remember hearing something once about adjusting the gas/air mixture for more efficient combustion. I have no idea whether the mixture is actually adjustable on a furnace. I know it is on my old gas stove.
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There is an optimal point of efficiency that is the perfect mixture of gas and oxygen. Rather than barbarity close or open anything and possibly cause problems, get a service tech to check your burner. He'll use an instrument to check oxygen content in the flue and adjust as needed.
We're installing O2 trim equipment on our boilers at work. It works very much like the fuel injection and emissions system on your car and will adjust every second as load changes and burner modulates. It is also $25,000 per boiler
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JohnR66 wrote:

Have you considered this line of products? http://www.intellidynellc.com/05_wintr.htm
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It is BS. you can actually damage your furnace or produce CO By doing this.
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As an inspector, I see a lot of things done that are a bit..different. I saw one that had taken a furnace designed to be mounted horizontally, under a floor in the crawl space. Person had mounted it in the basement above his existing unit, and the exhaust from the first was directed to the fire box of the one above. That one sent its output to a couple of bedrooms rather than having 'dueling fans'. Indeed, that second one recovered considerable heat from the first one, and the exhaust from it was still warm enough to maintain good venting. When I saw it, I was serving as a Health Dept. inspector on Haz-Mat duty, and my carbon monoxide detector was routinely verified to be in excellent function. Rather than modifying the existing unit, you might consider alternatives.

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On Sat, 13 Sep 2008 04:25:59 -0700, Michael B wrote:

Michael:
Do I presume correctly the second furnace was not connected to the gas line, and no fire in the firebox? The only heat in the 2nd firebox came from the exhaust of the first?
Wasn't there a problem with chimney back-drafting in winter? Or did this happen down South where you don't get temperatures below 10 degrees F?
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I was left with those questions and others too. It sounds like the second furnace was just being used as a heat exchanger to recover some additonal heat from the exhaust of the first furnace. I was also confused by the ending statement: "Rather than modifying the existing unit, you might consider alternatives. " Is he actually suggesting this double furnace arrangement as a sound alternative? And if so, I'd say that while not modifying the existing furnace itself, he is making a huge change in the overall heating system.
It doesn't sound very practical to me. In addition to having to somehow rig in a second furnace, you also have to consider that the second furnace, which presumably is acting as a heat exchanger only, has it's own blower. How much does it cost in electricity to run that versus the amount of extra heat being recovered? Then, factor in that to gain that additional heat, you are pulling air through ducts from the conditioned living space, heating it only slightly, then sending it back. With typical duct work, you might very well give back much of the energy being gained due to heat loss as it's being moved around.
It would seem to me that from any practical sense, if you want to get more heat out of a gas furnace, just buy a high efficiency one.
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When I observed this, here in Louisville, high efficiency furnaces were extremely expensive. The guy had run supply and delivery duct from the bedrooms, they only got heat when the other unit was running, and indeed, they stayed warm too, giving indication of the extent of heat to be recovered with an old unit. If I had been doing it, my efforts towards heat recovery would have been on a water heater, which typically has more loss because of its design. I've seen some interesting arrangements with vehicle exhaust tubing and computer fans. Here, the January average temperature is 30 degrees, with infrequent excursions into the single digits.
On Sep 13, 9:31am, snipped-for-privacy@optonline.net wrote:

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By the way, the existing furnace was a hot water system unit, built during the days that it was more expensive to meter the gas than for the actual gas. My, things have changed.
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And what do you loose in increased cost to run the blower, they pull alot of power. Just set it to spec and have it completely cleaned.
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old furnaces were commonly massively oversized...........
the longer a furnace runs the more efficent it is..........
so throttling back a really old furnace might save a little energy, at the risk of CO2 poisioning if the exhaust gas isnt hot enough to draft up the chimney.
Its probably not a good idea, but some people might try it.
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That's simply the dumbest thing I've heard in a while. Do not do this or your asking for problems!
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