I would also think that one of the functions of the paint
is to protect the aluminum from the elements, like
road salt. If painting them made any significant difference
in performance, then they would also paint other aluminum
condensers, like home central AC units. I haven't seen
one of them with paint......
what some people believe to be true and what is actually true aren't the
same thing. most small shops run on artisanal tradition, not science -
they may believe there's no negative impact of doing something, but i
doubt any but a very few have ever actually tested.
1. The black coating improves heat loss by radiation. But, since very little
of the actual heat loss from the condenser is by radiation (most is from
convection), it doesn't really make much of a difference.
2. Putting a layer of something on the outside of the aluminum will indeed
reduce heat transfer a little if that something is a poorer heat conductor
than aluminum.... but indeed since a layer of paint is thin it doesn't
really make much of a difference.
If I were making condensers, I would do black anodizing. You get a nice
black surface, you don't get much change in heat transfer since there really
is no coating, and you get something nice and hard that is much more resistant
And that's really the main issue... corrosion builds up and both provides an
insulating layer and eventually eats the fins away until you don't have as
much surface area anymore.
"C'est un Nagra. C'est suisse, et tres, tres precis."
a room AC to cool a room with the volume of a dozen cars for $100.- Hide qu
oted text -
For the same reason that it could cost several hundred to fix that
room AC, if it failed. And the fact that the components of an auto
AC are usually not very accessible. The evaporator for example,
is buried in the dash. You can't just take off a couple pieces of
outer sheetmetal off and get to everything right in front of you....
With labor rates at $100, what do you expect?
$1200 is if it's an easy job. I've heard of several that were nearly
$2000. My Brotherinlaw's Volvo needed $2000 in repairs and a year
later it broke again and they wanted another $2000 to fix it. He did
as they hoped, he bought a new car.
y a room AC to cool a room with the volume of a dozen cars for $100.
First, it doesn't always cost $1,200 to fix a car AC. If it's a bad
switch or a corroded wire to the compressor it could be $100.
If it's leaking shrader valves, it could be $250.
Second, you're comparing the cost to repair something with the
price of a new cheap, mass market appliance built on a high volume
assembly line. If that $100 air conditioner had a compressor that
failed, shred metal bits, contaminating the whole thing, what do
you think it would cost to diagnose it, take it all apart, flush it,
braze in a new compressor, recharge, test it, etc? It would be many
times the $100 it costs for it to begin with, so it just isn't done.
throw away the auto AC as a unit and get a new one, so you have to
deal with what's there. The factor in that half the system, ie the
evaporator, TXV valve, blower, etc is buried under the dash where
a lot of stuff potentially has to be removed if that part needs
Also, how much it cost to fix a car AC is highly dependent on
the parts used. Go to the dealer and pay for a new OEM
compressor, receiver/dryer, etc and it's a lot of money. Kind of
like buying a shelf or plastic part for a fridge. Use an
independent shopt that will offer a rebuilt compressor, aftermarket
parts, etc and the price can be hundreds less.
It's mostly the labor costs. But parts can be costly too, compared to
a window unit. Window unit compressors are hermetically sealed with
the driving motor, cars compressors are belt driven. Pretty sure car
condensers are bigger and more costly. Don't know why.
Ever replace a car A/C compressor, condenser or evaporator?
Lots of labor digging them out and putting them in.
Pretty sure car A/C shops charge you for refrigerant, even if they
pulled yours for recycling.
But it mostly car mechanic manual labor vs automated factory labor.
In fairness to the price disparity, the home unit also includes an
EXTRA motor to drive teh compressor (in the car the motor comes with
the car so it's "free") and the home unit also includes a condenser
fan this is similarly "free" in the car. And the home unit also has a
blower fan that, in the car, is again, "free". Likewise, the duct
work in the car is "free". The extra cost to add AC at the factory to
a modern car is really pretty low, I'd bet the parts don't amount to
more then $500 and the extra labor perhaps $100.
n buy a room AC to cool a room with the volume of a dozen cars for $100.
I see folks throwing out all kinds of numbers for how many btus
or tons a typical auto AC is, but I haven't seen a reference
that I'd call credible or rely on. And I'd bet the typical auto AC
isn't 3 tons.
It's probably more like half that. A car is a tougher environment
to cool than a house, but it's also a small volume. One thing that
suggest it's not 3 tons is the size of the equipment it takes to
get 3 tons of cooling. Anyone think for example the evaporator
in a car is anywhere near the size of one in a home 3 ton HVAC?
It's not designed for efficiency. My 2.5 ton home compressor is small
considering there is a motor in there. I recall in my air conditioning book
talk about vehicles. Big difference in full size vans vs small car.
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