Improving furnace AFUE
 

How much would the following improve efficiency? (20yo gas upflow in the
basement)

1. Make the furnace room airtight and add outside combustion air. This would
eliminate heated air from going up the chimney. There is already CA to the
return but this may not be enough.

2. Turn off pilot when not in use - 8 months/year

3. Increase the speed of blower by changing pulley

4. Set fan Limit switch to start fan sooner and stop later

I know the newer furnaces are 80-96% but I spend $800/yr on gas so the
payback will be too long.

1 maybe 5$ a year. 2 maybe 8 $ a year.
3 zero, and your fan may not last and electric should go up. 4 ?
maybe zero.
Payback? how long will you live there. If you are very lucky you are at
80%. and a 94.5% unit will save 18%. So say you are at 75% a 94.5% unit
will save apx 26% and that is at todays gas prices, in ten years gas
will probably be double

"HL" wrote in message
news:Jwtnd.194024$9b.140622@edtnps84...
How much would the following improve efficiency? (20yo gas upflow in the
basement)

1. Make the furnace room airtight and add outside combustion air. This
would
eliminate heated air from going up the chimney. There is already CA to the
return but this may not be enough.

2. Turn off pilot when not in use - 8 months/year

3. Increase the speed of blower by changing pulley



4. Set fan Limit switch to start fan sooner and stop later

I know the newer furnaces are 80-96% but I spend $800/yr on gas so the
payback will be too long.



If you are spending that amount on gas, your payback will be quicker....do
the math.

also, nothing you state above is worth your time, effort, and 3 and 4 are
bad for you.

You are forgetting electric blower consumption, an old unit may take 450
watts on low, mine did, my new unit takes 325, and a VS unit can take
200 or less. You will increase AC seer by 1 with a new VS unit and save
winter and summer on electricity, Now payback is a new calculation of
much less time.

"m Ransley" wrote in message
...
You are forgetting electric blower consumption, an old unit may take 450
watts on low, mine did, my new unit takes 325, and a VS unit can take
200 or less.

Most are much less, particularly if DC....

You will increase AC seer by 1 with a new VS unit and save
winter and summer on electricity, Now payback is a new calculation of
much less time.


Incorrect. You can loose SEER ratings unless the entire system is set up,
and MATCHED. You start throwing VS motors on units and unless its been
correctly set up , all kinds of things can start to happen.

CB ,what can happen, Im taking out a 2 speed 2 stage, 3 year old furnace
, all was new at the same time, putting it in the garage and getting a
VS DC. My AC is oversized since I insulated after the AC install and a
new smaller outside compressor is out of the question. The original
lennox guy was going to do it. The only thing I was told about was
freezing the coil on lowest speed , So If I get it instaled- matched
right I will be OK? Or what is the salesman not telling me .
And " who" is Hack`n Dave`s in Illinois .

"Steve@carolinabreezehvac" wrote
in message ...

"m Ransley" wrote in message
...
You are forgetting electric blower consumption, an old unit may take 450
watts on low, mine did, my new unit takes 325, and a VS unit can take
200 or less.

Most are much less, particularly if DC....

You will increase AC seer by 1 with a new VS unit and save
winter and summer on electricity, Now payback is a new calculation of
much less time.


Incorrect. You can loose SEER ratings unless the entire system is set up,
and MATCHED. You start throwing VS motors on units and unless its been
correctly set up , all kinds of things can start to happen.

just as bad throw VFD controls on the existing motor. VFD/VS should be
matched together for best performance.

After the 20 years of service this furnace has more than paid for itself.
Your now running on borrowed time. It's time for newer high efficiency
furnace. All the suggestions by the other tech's is true and correct. If
you are experiencing $800 gas bills from the heating system alone, a 96%
furnace will pay for itself actually in a short time.

--
Zyp
"SQLit" wrote in message
news:LAJnd.332832$a85.203173@fed1read04...

"Steve@carolinabreezehvac" wrote
in message ...

"m Ransley" wrote in message
...
You are forgetting electric blower consumption, an old unit may take
450
watts on low, mine did, my new unit takes 325, and a VS unit can take
200 or less.

Most are much less, particularly if DC....

You will increase AC seer by 1 with a new VS unit and save
winter and summer on electricity, Now payback is a new calculation of
much less time.


Incorrect. You can loose SEER ratings unless the entire system is set
up,
and MATCHED. You start throwing VS motors on units and unless its been
correctly set up , all kinds of things can start to happen.

just as bad throw VFD controls on the existing motor. VFD/VS should be
matched together for best performance.

Payback? how long will you live there. If you are very lucky you are at
80%. and a 94.5% unit will save 18%. So say you are at 75% a 94.5% unit
will save apx 26% and that is at todays gas prices, in ten years gas
will probably be double


I believe it's (old afue - new afue) / new afue lowering the savings to 15%
and 21%.


http://www.aceee.org/consumerguide/reheat.htm

HL there is no "old Afue" , recalculate using the 80% furnace as a
base for 100. . 80 is the baseline, so what is say 5 % of 80, more
than of 100 get it ??? Or figure the % difference of the 2 units on
each other, not 100 as a %

"Steve@carolinabreezehvac" wrote
in message ...

"HL" wrote in message
news:Jwtnd.194024$9b.140622@edtnps84...
How much would the following improve efficiency? (20yo gas upflow in the
basement)

1. Make the furnace room airtight and add outside combustion air. This
would
eliminate heated air from going up the chimney. There is already CA to
the
return but this may not be enough.

2. Turn off pilot when not in use - 8 months/year

3. Increase the speed of blower by changing pulley



4. Set fan Limit switch to start fan sooner and stop later

I know the newer furnaces are 80-96% but I spend $800/yr on gas so the
payback will be too long.



If you are spending that amount on gas, your payback will be quicker....do
the math.

also, nothing you state above is worth your time, effort, and 3 and 4 are
bad for you.


Aren't the 80% AFUE furnaces supposed to eliminate losses cause by the pilot
light and 24hr of paid heated air going up the chimney? Would not 1 and 2
eliminate most of those losses? Much efficiency loss would appear to be
caused by 2+ mins of burn before the fan comes on followed by 4 mins run
time. I suppose the new draft inducer design and faster fan startup
eliminate most of this.