"Clark W. Griswold, Jr." wrote in message
...
wrote:
The only thing I would add, which complicates things, is a
consideration of what time you turn the AC back on when you come home.
If you turn it on during the blazing hottest part of the day, the AC
has lots of work to do when it is least efficient--working against the
outdoor heat.
Well, sort of. A/C compressors are nothing more than heat transfer
devices. As
someone else posted, they aren't working harder of easier based on what
the
outdoor temps are. They consume the same amount of electricity.
AC compressors are nothing but a vapor pump. That's it. Kinda like the
water pump in your car.
A little refresher course: I'm making up the numbers, but the principles
hold.
Making up more than numbers.
An AC compressor takes a freon like gas and compresses it. Basic
thermodynamics
states that when you compress a gas it heats up. Lets say its 95 outside.
By
compressing the gas it goes up 15 degress to 110. If it were 70 outside,
it
would go up to 85. The 15 degrees from compressing doesn't change - that's
basic
thermo again.
Grab the discharge line of a properly charged AC compressor.
We run the compressed gas through an outdoor radiator and blow a fan
across the
radiator. That cools the compressed gas back down to outdoor temp - say
95.
Bring the gas inside and through a heat exchanger, only this time we let
the gas
expand.
Close.
Basic thermo says the gas gets colder, lets say by the same amount, so the
heat
exchanger temp is now 75. By blowing the 90 degree house air through a 75
degree
exchanger, the house gets cooler and the cycle repeats.
Again, close.