I have an old Singer furnace, model GL1406, which I'm told is over 30 years
old (I've owned the house for 23 years). Except for two recent minor
electrical problems which cut off power to the blower motor, the unit has
been working fine. I have been told, however, that the blower bearings are
not in great shape and I should get a new furnace and it would be a lot more
efficient. Our gas bills, in NYC, have been very high lately, but is it
worth $4500 for a new Carrier 80% efficient furnace + $800 for a "by-pass
humidifier" to gain that efficiency? Prices include installation and
readapting ductwork, plumbing and electric. Which other brands should I
consider?

Get bids 4500 may or may not be high, but getting an 80 % in your
location is foolish with future gas prices trends. Look at 94.5%
efficient units, you dont mention your gas heat cost.

Paul Isaacs wrote:
I have an old Singer furnace, model GL1406, which I'm told is over 30 years
old (I've owned the house for 23 years). Except for two recent minor
electrical problems which cut off power to the blower motor, the unit has
been working fine. I have been told, however, that the blower bearings are
not in great shape and I should get a new furnace and it would be a lot more
efficient. Our gas bills, in NYC, have been very high lately, but is it
worth $4500 for a new Carrier 80% efficient furnace + $800 for a "by-pass
humidifier" to gain that efficiency? Prices include installation and
readapting ductwork, plumbing and electric. Which other brands should I
consider?


I'b be more concerned with the contractor. I'd get some more estimates
and also strongly consider getting a 90%+ furnace. With energy prices
likely to climb even higher, I think the incremental cost is already
justified. I don't know what kind of re-adapting is required to put
in the new unit, where it's located, etc. But the tip off that
something is wrong here is that this guy wants $800 for a bypass
humidifier that's being installed at the same time as a new furnace?
You can get a top of the line Aprilaire 700 (which I highly recommend
as opposed to the bypass type) for $225 retail and installation,
especially at the same time as a furnace is not very difficult. IMO,
$800 is a rip off.

BTW, does that $4500 include air conditioning? I sure hope so!

gto with at least a 90 + furnace, 800 for a humidifer is too much too

get more quotes

This is Turtle.

Yes it is time for a new one because of furture gas prices.

I would concider a 90% afue or better.

$4500 + $800 for the humidity control may be too much as the group says
but what is too much for your area. Get you a second bid to just check
to see what too much is. i don'
t know the prices in your area and this $4500 might be normal for i
don't know.

The price of a job is only about 1/2 of the job but the other 1/2 is
the professional that will do a good job. So be more looking at what
company does the job than the price of it.

TURTLE

I can not imagine why anyone in any east coast location would want a
humidifier, ever. It's already too humid here year round.

we when you heat air the humidity level drops a lot, higher humidity
appears warmer so you can run a lower temperature and save energy

Paul Isaacs wrote:
I have an old Singer furnace, model GL1406, which I'm told is over 30
years old (I've owned the house for 23 years). Except for two recent
minor electrical problems which cut off power to the blower motor,
the unit has been working fine. I have been told, however, that the
blower bearings are not in great shape and I should get a new furnace
and it would be a lot more efficient. Our gas bills, in NYC, have
been very high lately, but is it worth $4500 for a new Carrier 80%
efficient furnace + $800 for a "by-pass humidifier" to gain that
efficiency? Prices include installation and readapting ductwork,
plumbing and electric. Which other brands should I consider?

I am with the rest. The price sounds too high, get more estimates and
do look for a more efficient furnace 80% is low by today's standards. I
would not go below 90%

--
Joseph Meehan

Dia duit

m Ransley wrote:

800 for a humidifier is to high, it does not add efficiency only
comfort.

Hi,
Not really. With proper humidity you can lower the temp. which means
saving. Less gas consumption = more efficency?

Joseph Meehan wrote:

Paul Isaacs wrote:

I have an old Singer furnace, model GL1406, which I'm told is over 30
years old (I've owned the house for 23 years). Except for two recent
minor electrical problems which cut off power to the blower motor,
the unit has been working fine. I have been told, however, that the
blower bearings are not in great shape and I should get a new furnace
and it would be a lot more efficient. Our gas bills, in NYC, have
been very high lately, but is it worth $4500 for a new Carrier 80%
efficient furnace + $800 for a "by-pass humidifier" to gain that
efficiency? Prices include installation and readapting ductwork,
plumbing and electric. Which other brands should I consider?


I am with the rest. The price sounds too high, get more estimates and
do look for a more efficient furnace 80% is low by today's standards. I
would not go below 90%

Hmmm,
No rebate from government when you do this kind of furnace upgrade?????????

On Sat, 11 Mar 2006 16:47:59 GMT, Tony Hwang wrote:

m Ransley wrote:

800 for a humidifier is to high, it does not add efficiency only
comfort.

Hi,
Not really. With proper humidity you can lower the temp. which means
saving.

Yes.

Less gas consumption = more efficency?

No.

Efficiency for a furnace is defined somewhere and shouldn't be used
differently by a furnace salesman. It relates to how much heat is
produced for a given amount of fuel. If a humidifier increased
effiiciency, then my furnace that is 27 years old would have high
efficiency because I have installed a humidifier.

wrote:
we when you heat air the humidity level drops a lot, higher humidity
appears warmer so you can run a lower temperature and save energy


Yeah, can't believe he really lives on the east coast. It's only
really humid here July/August. And humidifier, as you pointed out, is
useful in winter, when without one, with it cold outside, the inside
humidity can get very low. Maybe he likes getting static shocks?

mm wrote:
On Sat, 11 Mar 2006 16:47:59 GMT, Tony Hwang wrote:


m Ransley wrote:


800 for a humidifier is to high, it does not add efficiency only
comfort.


Hi,
Not really. With proper humidity you can lower the temp. which means
saving.


Yes.


Less gas consumption = more efficency?


No.

Efficiency for a furnace is defined somewhere and shouldn't be used
differently by a furnace salesman. It relates to how much heat is
produced for a given amount of fuel. If a humidifier increased
effiiciency, then my furnace that is 27 years old would have high
efficiency because I have installed a humidifier.

Hi,
I know but over all as a heating system if less gas is used it's same as
better efficiency, isn't it? Efficiency is ratio between energy input
vs. output. Theoretical maximum is 1(100%). Where I live, government
cushion, the gas price increase. No matter how high it goes, at certain
price and on, government picks it up in the form of rebate directly to
utility company. During heating season this policy is in force.

Paul Isaacs wrote:
Well, thanks everyone for replies. Yes I though $800 quite high for a
humidifier. My plumber who seems very honest recommended the hvac
company as being honest, but I'm not sure as hvac man keeps saying
he's honest. I definitely will get other bids and look to a higher
efficiency unit. As for wanting a humidifier with a forced-air
system, my house sure feels dry during heating season so that's a
definite plus for me. And no, the $4500 does not include AC. No one
mentioned other brand furnaces, my neighbor had a Trane installed a
couple of years ago for around $3500.

Don't worry about what brand furnace you end up with. The most
important part of the deal is the tech who will help pick the right
equipment and size and installation for your specific situation. A good
tech will choose good equipment for you. Brand names are not always an
indication of quality.


--
Joseph Meehan

Dia duit

"Paul Isaacs" wrote in message
news:PUEQf.386$Vb.312@trndny01...
No one mentioned other brand furnaces, ...


Because brand of unit is not the important part.

The _installation_ is.

I stress - The installation is the important part.

Get a couple more estimates. Google the equipment offered to you
and educate youself about which features of the units are
important to you. There are many things to consider besides
price. Noise level is one. Efficiency is another. There are a few
manufacturers that make 95% efficient furnaces and they will get
you a tax credit. Trane is not one of those manufacturers. Don't
be hasty and don't be afrain to ask specific questions.

wrote in message
oups.com...

wrote:
we when you heat air the humidity level drops a lot, higher
humidity
appears warmer so you can run a lower temperature and save
energy


Yeah, can't believe he really lives on the east coast. It's
only
really humid here July/August. And humidifier, as you pointed
out, is
useful in winter, when without one, with it cold outside, the
inside
humidity can get very low. Maybe he likes getting static
shocks?


Or maybe he lives on the East Coast of FLorida.

On Sat, 11 Mar 2006 12:35:55 GMT, "Paul Isaacs"
wrote:

I have an old Singer furnace, model GL1406, which I'm told is over 30 years
old (I've owned the house for 23 years). Except for two recent minor
electrical problems which cut off power to the blower motor, the unit has
been working fine. I have been told, however, that the blower bearings are
not in great shape and I should get a new furnace and it would be a lot more
efficient. Our gas bills, in NYC, have been very high lately, but is it
worth $4500 for a new Carrier 80% efficient furnace + $800 for a "by-pass
humidifier" to gain that efficiency? Prices include installation and
readapting ductwork, plumbing and electric. Which other brands should I
consider?



Your furnace works fine. The only critical factor to merit a furnace
replacement is if the heat exchanger is cracked and lets in toxic
combusted air into the house air circulation. Only then is it
mandatory and more economical to replace the furnace than to replace
the heat exchanger.

My Inter City gas furnace is 30 years old and looks as new as the day
it was installed. I had been coughing last season whenever my furnace
fired up. I asked the gas company for a FREE furnace inspection.
Your gas company should have a similar service. The technician gave
it a OK but said that the heat exchanger was already getting old.
Call for another inspection in the future if I suspect anything. He
also noted that I had put the fan in backwards. It will work but
won't blow that efficiently. Its easy to take out the fan and turn it
around to rotate the correct direction.

I spent $350 to get the furnace ducts cleaned, the only time in 30
years, and my coughing fits stopped.

25 years ago I swapped the 1/3 HP furnace blower for a 1/2 HP one from
my table saw. (I upgraded the table saw to 1 HP.) That motor has
been humming without trouble up to today. When I did the swapping I
also took out the squirrel cage blower fan to clean it. Reassembled
the stuff and it worked fine. After about a year's running the
furnace had an annoying thunk everytime the fan started or stopped.
So I tightened the fan belt, oiled the bearings and it will work fine.

This went on for 4 years until the thunks were rather disturbing and I
decided to take the fan out to clean it as well as check the
mechanism. The noise must be related to the fan as that was the only
moving part. The motor was fine. I found the bronze sleeve bearings
ovalled and the fan shaft worn and gouged quite deeply. I had
overtightened the fan belt. The tension wore into the bronze
bearings. Adding lube oil retained the metal filings to create an
abrasive slurry that gouged into the steel fan shaft.

The bearings are available from any appliance repair supplies shop.
They are meant to run without lubrication. Frankly the heat in the fan
chamber would distill off the light oil faction and leave a gummy
residue that is no good for lubrication. My 1/2 HP motor would have
overcome any frictional resistance without trouble where a 1/3 HP
motor might have overload burn out. The shaft is just be a 3/4 inch
diameter steel rod. The repairs were quite simple and can be managed
by anyone who is not all thumbs.

My advice for you is to get your gas company to give your furance an
inspection. He does not do repairs and has the obligation to give a
professional opinion on the safety aspects of your furnace. He also
has the obligation to report any serious furnace safety problems.
Besides gassing yourself your house can catch fire and burn down the
neighborhood in the process.

Take apart the blower fan assembly anyway and do a thorough clean-up
of that chamber. Obviously you do this only in the warmer months when
you no longer need the furnace running. You will be amazed at the
gunk and dust coats that had accumulated. Vacuum first. For stubborn
oilsoaked dust use varsol to wipe them off. A wet cloth and maybe some
soap should remove the rest. Then leave the chamber as clean bare
metal. Any oil or other coating will just attract dust which will be
baked onto the chamber walls. Much of the respiratory problems during
winter likely arise from the dust and gunk buildup lurking inside trhe
furnace.

The fan motor bearings are meant to run dry. My fan motor has been
running for more than a decade now without trouble. I check and clean
the fan chamber every three years or so. Do not add lube oil (ref.
abrasive slurry above). Set the hinged motor such that the standoff
screw will just hold the motor against the stop. The fan belt tension
should be from the weight of the motor, not by tightening the
standoff screw.

On Sat, 11 Mar 2006 06:58:17 -0600, (m Ransley)
wrote:

800 for a humidifier is to high, it does not add efficiency only
comfort.


Use an ultrasonic humidifier. Place a skirt under it to catch the
mineral deposits from the mist. You need moisture around you not in
the whole house. Whole house humidity can cause condensation leading
to mold and wood rot. Better still have a lot of house plants. They
respire and put moisture into the air as well as supply oxygen. Water
them sparingly. If the plants thrive so will you. The other
advantages of house plants will be self evident when you have them.

Furnace mounted forced air drum type and hallway drum type humidifiers
are more of a hassle than a help. The foam elements clog up with
mineral deposits very quickly and are hard to remove. Replacement
foam elements cost an arm and a leg. However my main objection is
that slime molds and mico-organisms find the wet tepid water an ideal
culture medium in which to propogate. If you ever have one or can
take a look at one you will find the water tray full of slimy strands
and films. They produce spores. The spore get blown into the air
with the furnace air. You have a health problem.

PaPaPeng wrote:
On Sat, 11 Mar 2006 12:35:55 GMT, "Paul Isaacs"
wrote:


I have an old Singer furnace, model GL1406, which I'm told is over 30 years
old (I've owned the house for 23 years). Except for two recent minor
electrical problems which cut off power to the blower motor, the unit has
been working fine. I have been told, however, that the blower bearings are
not in great shape and I should get a new furnace and it would be a lot more
efficient. Our gas bills, in NYC, have been very high lately, but is it
worth $4500 for a new Carrier 80% efficient furnace + $800 for a "by-pass
humidifier" to gain that efficiency? Prices include installation and
readapting ductwork, plumbing and electric. Which other brands should I
consider?




Your furnace works fine. The only critical factor to merit a furnace
replacement is if the heat exchanger is cracked and lets in toxic
combusted air into the house air circulation. Only then is it
mandatory and more economical to replace the furnace than to replace
the heat exchanger.

My Inter City gas furnace is 30 years old and looks as new as the day
it was installed. I had been coughing last season whenever my furnace
fired up. I asked the gas company for a FREE furnace inspection.
Your gas company should have a similar service. The technician gave
it a OK but said that the heat exchanger was already getting old.
Call for another inspection in the future if I suspect anything. He
also noted that I had put the fan in backwards. It will work but
won't blow that efficiently. Its easy to take out the fan and turn it
around to rotate the correct direction.

I spent $350 to get the furnace ducts cleaned, the only time in 30
years, and my coughing fits stopped.

25 years ago I swapped the 1/3 HP furnace blower for a 1/2 HP one from
my table saw. (I upgraded the table saw to 1 HP.) That motor has
been humming without trouble up to today. When I did the swapping I
also took out the squirrel cage blower fan to clean it. Reassembled
the stuff and it worked fine. After about a year's running the
furnace had an annoying thunk everytime the fan started or stopped.
So I tightened the fan belt, oiled the bearings and it will work fine.

This went on for 4 years until the thunks were rather disturbing and I
decided to take the fan out to clean it as well as check the
mechanism. The noise must be related to the fan as that was the only
moving part. The motor was fine. I found the bronze sleeve bearings
ovalled and the fan shaft worn and gouged quite deeply. I had
overtightened the fan belt. The tension wore into the bronze
bearings. Adding lube oil retained the metal filings to create an
abrasive slurry that gouged into the steel fan shaft.

The bearings are available from any appliance repair supplies shop.
They are meant to run without lubrication. Frankly the heat in the fan
chamber would distill off the light oil faction and leave a gummy
residue that is no good for lubrication. My 1/2 HP motor would have
overcome any frictional resistance without trouble where a 1/3 HP
motor might have overload burn out. The shaft is just be a 3/4 inch
diameter steel rod. The repairs were quite simple and can be managed
by anyone who is not all thumbs.

My advice for you is to get your gas company to give your furance an
inspection. He does not do repairs and has the obligation to give a
professional opinion on the safety aspects of your furnace. He also
has the obligation to report any serious furnace safety problems.
Besides gassing yourself your house can catch fire and burn down the
neighborhood in the process.

Take apart the blower fan assembly anyway and do a thorough clean-up
of that chamber. Obviously you do this only in the warmer months when
you no longer need the furnace running. You will be amazed at the
gunk and dust coats that had accumulated. Vacuum first. For stubborn
oilsoaked dust use varsol to wipe them off. A wet cloth and maybe some
soap should remove the rest. Then leave the chamber as clean bare
metal. Any oil or other coating will just attract dust which will be
baked onto the chamber walls. Much of the respiratory problems during
winter likely arise from the dust and gunk buildup lurking inside trhe
furnace.

The fan motor bearings are meant to run dry. My fan motor has been
running for more than a decade now without trouble. I check and clean
the fan chamber every three years or so. Do not add lube oil (ref.
abrasive slurry above). Set the hinged motor such that the standoff
screw will just hold the motor against the stop. The fan belt tension
should be from the weight of the motor, not by tightening the
standoff screw.
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?

In article FREQf.17$Rb.1@trndny05, "Paul Isaacs"
wrote:

the $4500 does not include AC.

That sounds pretty high to me.

Three weeks ago I replaced my old, natural draft furnace.

Using my friend/HVAC perfectionist's suppliers, we installed the system with
my obligation being only his costs. He and I go back 40-years, he was a
groomsman at my wedding 32-years ago. I have seen the actual invoices.

Total REAL cost before tax: $1786.

$640 - WeatherKing 92% condensing furnace ("92.8%" AFUE)
255 - Evaporator coil assembly
891 - Rheem 13 SEER outdoor air conditioner

Of course, that does not account for the relatively minor bill from the sheet
metal supply house, the fancy, right angle pleated filter housing and sundry
supplies. Nor does it account for the adult beverages and fuel for hauling my
friend around. I am quite pleased with the job. It was a VERY valuable
learning experience for me. I might even be able to do it MYSELF again - in
my next life! HA!
--

JR

First, the price sounds high. I'm in western NYS, and my boss gets
about two grand for a 80% furnace, and not much more for the
humidifier.

Like folks say, the humidifier doesn't add much work when done at the
same time. And the 90% furnace is an excellent idea.

I live in NY state. When it's winter, and there is snow on the ground,
there is a definite need for humidity in houses. And in summer, there
is a definite need for dehumidifying.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

wrote in message
oups.com...
I can not imagine why anyone in any east coast location would want a
humidifier, ever. It's already too humid here year round.

From what I know, Trane runs a bit expensive. If you can get a Trane
for 3500, the Bryant guy sounds high.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"Paul Isaacs" wrote in message
news:FREQf.17$Rb.1@trndny05...
Well, thanks everyone for replies. Yes I though $800 quite high for a
humidifier. My plumber who seems very honest recommended the hvac
company as
being honest, but I'm not sure as hvac man keeps saying he's honest. I
definitely will get other bids and look to a higher efficiency unit.
As for
wanting a humidifier with a forced-air system, my house sure feels dry
during heating season so that's a definite plus for me. And no, the
$4500
does not include AC. No one mentioned other brand furnaces, my
neighbor had
a Trane installed a couple of years ago for around $3500.


"Paul Isaacs" wrote in message
news:LuzQf.1$Ub.0@trndny07...
I have an old Singer furnace, model GL1406, which I'm told is over 30
years
old (I've owned the house for 23 years). Except for two recent minor
electrical problems which cut off power to the blower motor, the unit
has
been working fine. I have been told, however, that the blower
bearings are
not in great shape and I should get a new furnace and it would be a
lot
more efficient. Our gas bills, in NYC, have been very high lately,
but is
it worth $4500 for a new Carrier 80% efficient furnace + $800 for a
"by-pass humidifier" to gain that efficiency? Prices include
installation
and readapting ductwork, plumbing and electric. Which other brands
should I
consider?

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.

Tony Hwang wrote:

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.

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.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

On Fri, 17 Mar 2006 03:09:13 GMT, CJT 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...mo/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/produ...as_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.

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.
--------------------------------------------------------------------------------------------------------------------

the 90% is safely vented using plastic pipe at just ocver ambient temp
by using a secondary heat exchanger.

plastic being non corrosive is actually safer in this application since
steel or glvanized will rot out.

heat exchangers on 90+ furnaces are stainless steel to inhibit corosion.

I measured my 93% unit pvc stack at 90f and that was with a very dirty
air filter.