PaPaPeng wrote:
On Sat, 11 Mar 2006 21:55:39 GMT, Tony Hwang wrote:


Hmmm,
Your old furnace may be working OK but it is of old technology with LOW
efficiency! Would you drive a car of '60s? Gas guzzling, polluter?



Two questions. What is the payback on a furnace replacement? How
many years do you need to run the furnace to save in fuel the expense
used to pay for the replacement.

The second question is what is the technical explanation for the newer
furnaces to claim that it is more efficient than the older models?

A home furnace is simply a heat exchanger extracting heat from a
flame. The BTU output for a particular flame is a finite qualtity.
The increase in efficiency can only come only from the heat
extraction process. If the heat exchanger is built like a car
radiator in having lots of surface area then yes, there will be
greater efficiency. But the heat exchanger functions in a pretty
hostile environment. A delicate car radiator like device won't last
too long in a furnace. So the heat exchanger is built of crude cast
iron and there are only so many things you can do with this material.
I can't picture any significant design advance between the old and the
new heat exchanger elements. If you know of another explanation I am
ingterested.


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.