The 15 degree difference does not pertain to indoor versus outdoor. It
pertains to the indoor air temperature entering the evaporator unit compared
to the cool air leaving the evaporator unit. This indeed depends somewhat
on the outside temperature, but not as much as you might think. It also
depends on the airflow speed. I generally see it run from a 15-degree
difference to a 20-degree difference.
That is, if the temperature of the air in the house is 75F, then the
temperature in the plenum entering the cooling chamber is 75F, and then the
temperature in the air plenum right after the cooling chamber should be
between 55F and 60F. Note, the temperature at the grills where the cold air
enters each room will be a bit higher.
Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Chair, Division of Natural and Applied Sciences
Bluffton University
1 University Drive
Bluffton, OH 45817
419.358.3270 (office)
edmiston@bluffton.edu
-----Original Message-----
From: Dr Holly Priestley
Sent: Wednesday, August 24, 2011 7:01 AM
To: 'Forum for Physics Educators'
Subject: Re: [Phys-l] cooling hints
In regards to a/c cooling -- may have changed a bit but many, many years ago
when I was married to my son's father, he was an a/c repair person for part
of his working life. He would always tell me that and a/c can lower the
inside temp about 15 degrees and that is all. So, if it is 103 degrees out,
like we had this summer (NOT heat index, plain, ordinary pre-meteorologists
temperature), you will be lucky to have your house cool at 88 degrees. Of
course, a lot depends on insulation, sun through the windows, children/pets
running in and out, etc.
Holly Priestley