I understand why new furnaces are more efficient, but why AC?

Posted by mm on November 5, 2009, 8:40 pm

I think I understand why new furnaces are more efficient, but why AC?

I finally read an explanation about the exhaust air being cooler, as
low as 90 degrees F from gas furnaces, and more heat extracted from
the fire to heat the house, in new furnaces. I presume new oil
furnaces are more efficient the same way.

But why are new AC's more efficient. There is no cold air going up
the chimney with an old AC. I presume that if the refrigerant doesn't
lose all its coldth, warm up to room temperature, in the AC evaporator
inside the main air duct, when it returns to the condensor, it's that
much easier to condense because it is colder, and less heat has to be
radiated out from the condensor fins. So iiuc there is no loss there,
at least if that pipe is insulated.

So why are the new ACs more efficient?

Posted by Oren on November 5, 2009, 8:57 pm

wrote:

>So why are the new ACs more efficient?

Not a single clue, here.

By next January R22 (?) is illegal?

I'm being bombarded with these "energy credit" savings ads for a new
HVAC unit.

My unit is 12 years old...

It might work in may case?

Posted by mm on November 5, 2009, 9:03 pm

>wrote:

>>So why are the new ACs more efficient?

>Not a single clue, here.
>By next January R22 (?) is illegal?
>I'm being bombarded with these "energy credit" savings ads for a new
>HVAC unit.
>My unit is 12 years old...
>It might work in may case?

They'll sell you anything. It doesn't mean you need it. But I have
no idea.

Posted by on November 5, 2009, 11:31 pm

>By next January R22 (?) is illegal?

That is not exactly true
On Jan 1 they can't make new R-22 systems unless they are filled with
recycled R-22. They can still make new R-22 for repair of that system
tho.
It really sounds like there is a lot of room to cheat if someone
wanted to. I am still not convinced there ever was anything to the
freon scare. China and India have been going full blast, manufacturing
R12 and R22 systems for their people since "Montreal" in the late
90s.. Without the punishing taxes, I doubt they recycle any of it.
Even with all the recycling, virtually all freon gets vented anyway
from leaks. That is why they will still be able to make it until 2010
for "repairs".

In spite of all of this new freon in the world. the ozone hole that
everyone had their panties in a wad over, shrunk.

Posted by Lp1331 1p1331 on November 6, 2009, 1:12 am

The first thing about newer high efficiency a/c is the coil size-- both
condenser and evaporator. A new 2 ton unit is physically larger than
most 5 ton units of yesteryear. Scroll compressors (that most but not
all use) are somewhat more efficient than recips. The condenser coils
themselves, as well the whole condenser fan assembly are designed-- with
computer aid, not available years ago-- to get the optimum airflow with
much lower horsepower fan motors than old units, as are the evaporators
also.. All the motors-- condenser fan, blower, and compressor, have been
"tweaked' to maximum efficiency. Most all higher SEER units use
expansion valves instead of fixed orifice or capillay tube refrigerant
flow control. A few 13 SEER units use flowrator (fixed orifice) , but
pretty much all above 13 are TXV. Most all 16 + SEER units are two
stage, some even having two compressors. Just as with fuel mileage on
cars, the manufacurers have gotten all the easy gains in efficiency they
are going to get. Barring some breakthrough invention, future efficiency
gains will be small and costly. HTH Larry

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