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Posted by Colbyt on October 6, 2005, 10:54 pm
> googlemail2003@yahoo.com wrote:
> > We are planning on a new gas furnace next month. We have gotten
> > several estimates and some conflicting advice. One person told us to
> > get a 90% efficient furnace. It will require venting from the side of
> > the house. The second person said that these vents can freeze up in
> > the winter and cause flooding in the basement and possible carbon
> > monoxide troubles. He suggested the older type, an 80% efficient
> > furnace which can use our existing roof vent.
> 90% furnace vents freezing up and flooding the basement? Right. I'd
> suggest you get another estimate to compare with the one from the first
> person, and don't bother calling back the second person.
> I've lived with a 90% furnace since 1985 here in St. Paul, MN, where it
does
> get rather cold in the winter. Never had the intake or exhaust pipes on
the
> furnace freeze up. I have had some neat looking icicles form around the
> exhaust pipe in really cold weather from time to time, but it never
blocked
> the pipes.
> Only time a 90% furnace could freeze up is if it's installed in an
unheated
> attic.
> > Apparently the water being sent out by the newer types is from
> > condensation? This surprised me since our house is always SO dry in
> > the winter that we need to use a humidifier.
> The 90% furnaces use a sealed combustion chamber; outside air is brought
in
> via one PVC pipe, heated and exhausted out the second pipe. The heat
> exchangers pull so much heat out that the exhaust leaving the furnace is
> only warm and it forms condensation, which is drained out via a hose. By
> the way, the stuff that comes out is acidic, so don't drink it.
> One advantage to the separate air and exhaust on the furnace is when it's
> running it's not pulling air in around doors, windows and other leaks in
> your house. Oh and the reason they call them 90% efficient is 90% of the
> heat created is used to warm your house, with the remaining 10% going out
> the exhaust vent.
> > As for the problem with freezing - if we went away for a month could
> > we expect to come back to a basement full of water? Naturally we
> > would want to set the heat down low (65 or so).
> A basement full of water? Naaa. Maybe a few gallons if the drain hose on
> the furnace was disconnected. Now if the furnace were turned off in
> sub-zero weather, well, then you are looking at burst pipes.
> > The 80% furnace is cheaper but will require some type of air exchange
> > installed. Guess what we have doesn't meet code. That means that
> > getting the 80% won't really save us much money over the 90%. On the
> > other hand I don't want to have to worry about problems. That's why
> > we are getting rid of our old furnace in the first place.
> When I had my furnace put in back in '85, I also looked at 80% and 90%
> furnaces. Yes, there was a large price difference between the two, until
I
> factored in that would need a flue liner installed in my chimney with the
> 80% furnace. Seems one contractor forgot to include that in his estimate,
> but the company I went with pointed that out when I got quotes from them
on
> both an 80 and 90% furnace. Also, you may need a fresh air intake for the
> 80% furnace so it can draw outside air when it's running. The air
exchanger
> that you were quoted may take care of that, but they are expensive.
> > Advice and/or experiences would be much appreciated.
> Hope this helps.
> Bob.
I agree with Bob.
Never had a problem with a 93% dripping on the driveway yet.
Colbyt
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> several estimates and some conflicting advice. One person told us to
> get a 90% efficient furnace. It will require venting from the side of
> the house. The second person said that these vents can freeze up in
> the winter and cause flooding in the basement and possible carbon
> monoxide troubles. He suggested the older type, an 80% efficient
> furnace which can use our existing roof vent.