Re: Gas furnace replacement

On Fri, 17 Mar 2006 03:09:13 GMT, CJT <abujlehc@xxxxxxxxxxx> wrote:

Hi,
Cast iron exchanger? Mine does not looks like rusty cast iron! It looks
shiny. And there are high efficiency furnaces with efficiency of >90%
which waste LOT less gas. Pay back period is important but as a good
citizen aren't you interested in contributing to energy conservation and
less pollution?
And non-renewable energy source like NG and dino-juice price can only
go up in coming years. I and my family are trying to do our part to help
strained mother earth. How about you and yours? Also my government gives
rebate when we do things to conserve energy. Of course they don't foot
the whole bill but at least they help out. When I replaced my toilet
with a low water consumption model, city gave me 75.00. For furnace
upgrade it can be ~1000.00 depending what is done.


I just came from a friend's new home in Lethbridge and took a look at
his new furnace (900 sq ft home). Its less than half the size of mine
and has electronic ignition. The burners look simple enough but I
couldn't see the heat exchanger. I'll probably visit the local gas
company someday to see the latest technology. That said I can say
for sure that there is nothing complicated in his furnace layout that
would suggest any breakthroughs in heat extraction technology. There
is only so much heat a heat exchanger can absorb (rate of absorbtion)
at any given time. Like him I set my winter temp at 17 deg C. The
odd thing is that I felt a lot colder in his house. My best
explanation is that his small furnace has a much smaller blower motor
and fan

[For an air standard engine with g = 1.4 , compression ratio rC = 15
and expansion ratio rE = 5, this gives an ideal diesel efficiency of
56%. http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/diesel.html
(A gasoline engine is something like 40 percent. ) For a free
burning furnace flame most of the burnt hot air goes up the stack
(feel how hot the exhaust stack is) the efficiency is in the ~30 per
cent range, not > 90 percent.]

But from
http://www.columbiagaspamd.com/products_services/natural_gas_furnace.htm

[Efficiency:
Modern natural gas furnaces achieve operating efficiencies as high as
96 or 97 percent AFUE (Annual Fuel Utilization Efficiencies) and thus
give the homeowner 96 cents worth of heat into the living area for
each dollar of gas purchased. The minimum efficiency standard for
furnaces sold in the U.S. is 78 percent. While the typical furnaces of
years past used chimneys, the high efficiency units of today extract
so much heat from the gas they use that they can be vented through the
sidewall of your home using plastic pipe. This venting is similar to
the type of venting associated with a clothes dryer.

Pilot lights, which were used in older equipment, have been replaced
with spark ignition systems to save energy. ]

I am suspicious as to how this >90% efficiency is calculated as it
would mean that the stack plenum temperature at the furnace should be
close to ambient temperature, a practical impossibility. It didn't
occur to me to see the exhaust stack but it looked like the regular
galvanized steel. I would never accept plastic pipe (above article)
for this installation anyway.



I hope you scrapped the SUV. That'll save a lot more energy than
anything you do with your furnace in many areas of the world.


You are referring to Tony. Me? I don't own a vehicle anymore. Just
the trusty bicycle for getting around, by bus for longer distances or
a rental when needed.
.

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