Last night I decided to turn on my CAC for the first time in
anticipation for the upcoming warmer weather for the next few days.
Everything seemed to be OK. The compressor came on, and the indoor
blower came on. I also checked the pipe coming out of the compressor to
see if it was cold, but it did not seem "as" cold as it should. When I
looked in the sight glass I could see the freon flowing OK.
My question is being that it was only about 68 degrees outside last
night, does that affect the operation of the CAC, and thus why the pipe
did not feel cold? I remember last year when a service guy came over to
check the A/C, he said it should be checked optimally when it is warm
outside, plus he put a plastic bag around the unit to increase the
"head " pressure so he could get a more accurate reading on his gauges(
By the way, the unit checked out OK last year.) What does head pressure
I'm just trying to educate myself a little with how CAC works . Thanks
I am going to suspect that either the unit is not performing as it
should do any many possible problems, or that it simply did not "feel" as
cool as you would expect because it was already cool and the difference was
not all that much.
The sight glass should be fairly clear, with only a few bubbles passing
by to show the flow. If it is white and hazy, then the system likely
needs a charge. A plastic bag to increase head pressure? Head
pressure is a term that isn't always applied correctly, but what he
acheived is an increase in the pressure at the condensor coil because
the bag aound the unit prevents air exchange which doesn't allow the
condensor to shed heat from the compressor. Why he considered this to
be better accuracy evades me, because a running system is checked on
both sides of the compressor (only an example: the high side after the
compressor having 115psi and the low side having 25psi). It's the
pressure difference that causes cooling. The simplest analogy is an
air hose. An air compressor pressurizes the air in the hose. As it
leaves the hose the pressure drops, and the air is cooler. For a crash
course, take a look at
Thanks for that link. I learned a lot. Today was a lot warmer so I
turned on the A/C and this time I went to the A coil on my furnace. I
removed the access panel and felt the pipes were cold after the
expansion valve and throughout the coil.Also it felt cold blowing
against my face. Plus I saw condensation dripping into the pan so I
guess its doing its job as far as removing the humidity.
In an unrelated matter, I noticed that my attic fan was not turning on.
So I went into my attic and to my surprise I heard the motor humming. I
tried turning the blades, but it did not want to go. So I had a seized
motor. I picked up another motor at HD so I'll put it in tomorrow. The
attic fan really makes a difference as far as keeping the house cool.
I also noticed a problem with my new Honeywell T-Stat. ( look for a
That brings up another possibility. The A/C is not going to be able to
cool as well as it might as long as the humidity is high. When a home has
been open for some time to the outside air and when that air has been moist,
the house also absorbs a lot of moisture. It can take a few days to dry out
the house (rugs, wood etc.). In the mean time it may appear that the A/C is
not doing it's job. Just how much effect this is depends on a number of
factors so it may not always apply.
My old home and a home of a friend of mine suffered this greatly and it
often took three days or more each season before the house was dried out and
things were comfortable inside. My current home takes just a few hours.
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