CAC startup question

[Mikepier]

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 mean? I'm just trying to educate myself a little with how CAC works . Thanks

[Joseph Meehan]

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.

[jim_duprey]

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

[Mikepier]

jim_duprey wrote: . For a crash

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 seperate thread).

[Joseph Meehan]

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.