On Mon, 15 Nov 2004 20:42:55 GMT, "MLD" wrote:


"Doe John" wrote in message
.. .


Still worth it. Check your Utility Company--There are all kinds of
rebates
and incentives that pay off very well (up to $400) especially if you get
the
92% with variable speed blower. Also, where do you think the air (large
volume) for combustion comes from with the 80% furnace? It's air from
within
your house--all having been previously heated ($$$) and then thrown up
chimney--it, air, then it has to be replaced with (cold) outside air
which
is what gives you the drafts and air leaks and also because it has to be
heated, increases your costs. I think that your house stays more evenly
heated by using the outside air for combustion.
MLD


Can the ouside vent coming into the house be blocked by snow?

Also, I don't understand why using previously heated air for
combustion is worse than using cold air from outside? Any faqs on
this?

Based on my experience---Blockage is not an issue. Don't forget, this is a
4 in. pipe and the vent is blowing out warm air--approx 80-90F ( I think)
and it certainly can blow away/melt snow.
Noting wrong with using previously heated air for combustion except that you
have already paid to heat it to room temperature and then throw it up the
chimney. Then as noted, you have to replace this air and it comes from the
outside and it has to be heated to room temperature. You pay to heat air
that you're going to put up your chimney----wasted $$$$$$. We're talking
about high volumes of air.

I agree, and would add that cold air is dry air. The colder, the
drier. All of that outdoor air infiltrating into your home will tend
to lower the humidity. Then you pay to humidify it as well as heat it.

Gary R. Lloyd CMS
HVACR Troubleshooting Books/Software
http://www.techmethod.com