90% plus afue furnace disadvantages?

[hazmat]

Any reason not to go with the dual heat exchanger forced air furnaces?

I'm adding HVAC to my third floor media/play room. heating guy quoted an 80% unit, - mentioned something about the condensation freezing in the 90+% unit (it will be located in attic area - currently uninsulated, but I can change that if needed.)

Seems to me that natural gas prices aren't going to get cheaper in the long run, plus there are significant rebates available from the utiltiy as well as the furnace mfg for going high effeciency. What am I missing???

 

[hazmat]

Any reason not to go with the dual heat exchanger forced air furnaces?

I'm adding HVAC to my third floor media/play room. heating guy quoted an 80% unit, - mentioned something about the condensation freezing in the 90+% unit (it will be located in attic area - currently uninsulated, but I can change that if needed.)

Seems to me that natural gas prices aren't going to get cheaper in the long run, plus there are significant rebates available from the utiltiy as well as the furnace mfg for going high effeciency. What am I missing???

 

[Sigarms]

Hate to admit this, but not sure what you mean by a "dual heat exchanger"?

Live in N.C, just replaced my 90+ gas/A/C with an 80% variable speed gas furnace with a heat pump in my attic. Run the heat pump down until 45 degrees or so, then the gas furnace will kick on. Saves run time on the gas furnace using the heat pump for heating. So far, 91 degree temp coming out of the regsiters when running the heat the pump. With the price of propane, less I have to run the furnace, the better.

A 90 plus furnace is also known as a "condensing furnace" which means that you will need to get rid of water created by the furnace. Thus the "issue" in an unconditioned attic.

For myself, there are/were ways to prevent any issues with water, but went with the 80% sealed cumbustion furnace because I could not justify the price difference between a variable speed 80% compared to a variable speed 90%. Using the heat pump for heating, run time on the furnace for "emergency heat" will be minimal in N.C.

Being in N.C compared to New England, I will be running my A/C longer and my furnace "shorter" than you.

 

[Sigarms]

Hate to admit this, but not sure what you mean by a "dual heat exchanger"?

Live in N.C, just replaced my 90+ gas/A/C with an 80% variable speed gas furnace with a heat pump in my attic. Run the heat pump down until 45 degrees or so, then the gas furnace will kick on. Saves run time on the gas furnace using the heat pump for heating. So far, 91 degree temp coming out of the regsiters when running the heat the pump. With the price of propane, less I have to run the furnace, the better.

A 90 plus furnace is also known as a "condensing furnace" which means that you will need to get rid of water created by the furnace. Thus the "issue" in an unconditioned attic.

For myself, there are/were ways to prevent any issues with water, but went with the 80% sealed cumbustion furnace because I could not justify the price difference between a variable speed 80% compared to a variable speed 90%. Using the heat pump for heating, run time on the furnace for "emergency heat" will be minimal in N.C.

Being in N.C compared to New England, I will be running my A/C longer and my furnace "shorter" than you.

 

[hazmat]

Most (All?) of the 90+ efficiency units use a second heat exchanger to extract the extra 10-15% (vs the 80%). see page 4 of this carrier pdf infinity furnace


A heat pump is pretty much a non starter with the typical NE winter temps.

 

[hazmat]

Most (All?) of the 90+ efficiency units use a second heat exchanger to extract the extra 10-15% (vs the 80%). see page 4 of this carrier pdf infinity furnace


A heat pump is pretty much a non starter with the typical NE winter temps.

 

[Sigarms]

AKA "secondary" heat exchanger /forums/images/graemlins/blush.gif

You will be paying "top dollar" for the Carrier name no doubt.

 

[Sigarms]

AKA "secondary" heat exchanger /forums/images/graemlins/blush.gif

You will be paying "top dollar" for the Carrier name no doubt.

 

[Birdhunter1]

The HVAC guy that gave you an estimate is correct, the 90% furnace should not be put in the unconditioned area of your attic because it will freeze up the drain.
If you find another place to put it in a conditioned area the drain also should not be run outside because it will freeze there as well and thus not drain the furnace and cause 10 types of ****.

Can the furnace be put in a small closet in this game room and the drain be run downstairs?

 

[Birdhunter1]

The HVAC guy that gave you an estimate is correct, the 90% furnace should not be put in the unconditioned area of your attic because it will freeze up the drain.
If you find another place to put it in a conditioned area the drain also should not be run outside because it will freeze there as well and thus not drain the furnace and cause 10 types of ****.

Can the furnace be put in a small closet in this game room and the drain be run downstairs?