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Posted by Zyp on January 10, 2008, 2:44 am
Bubba wrote:
> On Mon, 7 Jan 2008 14:13:24 -0800 (PST), "Daniel J. Stern"
>
>> We have gas-fired central heat with A/C in our old 2-story (+
>> basement) house. 3-year-old Lennox air handler is in the basement.
>> This house has been badly abused in the past, and ductwork has been
>> mutilated. Air return capacity is grossly insufficient: the one and
>> only air return is on the main floor, and it is the ~4" x 10" size of
>> a regular heat register. There are eight supply registers throughout
>> the house, nine if we count the one in the basement, some of which
>> are oversize, so obviously one small register hole just isn't
>> enough. The return duct goes audibly into vacuum when the furnace
>> blower turns on (metal walls of the duct "pop"). To alleviate this
>> condition, I removed the blockoff plate from the return duct in the
>> basement. This plate covered where a humidifier used to be
>> installed. I put some wire mesh over the hole and some spun-fibre
>> filter batting over the mesh. This relieved the vacuum condition on
>> the return duct, but is probably less than optimal (basement is
>> smelly/mouldy/dusty) and may be against code (distribution air
>> intake in the same space as combustion taking place -- don't know if
>> that's problematic or not.)
>>
>> It occurs to me a flex duct could be run from the return duct (using
>> the blockoff plate hole) to a pass-through in an unused door from
>> the basement to outside, and a rodent/leaf/waterproof exterior air
>> intake could be put on the outside. This would take supply air from
>> outside the house and duct it to the air handler. Now here's the
>> question: What would be the effect on system efficiency by doing so?
>> I can think of two possible answers: Either the very cold outside
>> air would take much more energy to heat up to household temperature,
>> increasing the cost of running the system, or the greater
>> temperature differential between the fire and air sides of the heat
>> exchanger would mean more heat transfer to the supply air, reducing
>> the amount of heat wasted up the flue and not significantly
>> increasing fuel consumption to provide a given household ambient
>> temperature. Obviously the reverse (cool/ warm) of either situation
>> would apply during air conditioning season.
>>
>> So...which is it?
>>
>> Please and thank you,
>>
>> -DS
>
> You're going about it all wrong. All you need is some cardboard, duct
> tape, bailing wire and bubble gum. With that you can have a brand new
> efficienct system that everyone can enjoy.
> Bubba
And Bubba;
Don't forget the thermostat.
--
Zyp
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