HVAC help! Please!

[hesaias]

Its HOT in here!
Well, not too bad. Ive cleaned the coil, outside, and I have the gauges on the freon, but I have no idea what the readings tell me. Im gonna clean the evaporator coil tomorrow. Can anyone help a sweatting reefer out?

[jimhobbs]

What are the readings?:)

[hesaias]

51psig on the low pressure side, 195 on the high.

[hesaias]

and its 80f in the house, and about the same outside now.

[hesaias]

The temp pulled down over the night. Im gonna clean the evaporator today after work. I think I may have a low charge on the system, whadda you think?

[paranda]

Hello,
Your pressures look good for a R22 system with 80 ambient temperature. What size is the unit, and are you trying to cool a room or a house? Under ideal conditions, a properly sized unit will only cool the air about 20 degress. So if the air is 80 going in, it will be 60 coming out. Most people only turn on their A/C when it is already hot in the house, but that's not the best way to run the system. When you do that the A/C has to cool down the air until the temperature gets low enough to cool the house. This can take hours, makes the system run hard, and uses alot of energy. It is much better to turn the air on before it gets to hot. This way the A/C only has to maintain the temperature, runs better, and uses less energy.
Cleaning the coils is a great idea! Just doing that often solves allot of A/C problems. Another quick check that you can do is to feel the pipes next to the compressor. THe discharge (High side) should be hot. Be carefull, as it can be real hot and cause a severe burn! The suction (low side) should be nice and cool. The air coming off of the condenser coils should also be warm.
As for your pressures, a general rule of thumb is 50 - 55 PSI on the suction. For the discharge, look at the gauge. It has a scale with different Freons listed. Almost all home units use R22, unless yours was installed in the last few years (If it was, and you are using one of the newer refigerants, your gauges may not be calibrated for it and your reading will be false). Take a temperature reading, then add 20 degress to what you get. Find that on the scale and that should be your discharge pressure. So at 80 with R22, you would use the scale at 100. This would put your pressure at just under 200 PSI.
Do not add any Freon until you know for sure that is the problem! It is very easy to overcharge a system. This will not make it work any better and can cause severe damage to the system.
Sorry for the length, HTH
Peter

[hesaias]

Thanks man! I feel better knowing what im doing, instead of groping around in the dark:D

BTW, mine is a heat pump.

[KASESQ]

Some central HVAC units have overly long drain lines that can get clogged with schmutz over the years and back up. Also, making sure none of your cooling fins are bent is a good idea-these are like the fins on a car radiator and if they are bent flat they arent' dissipating the heat from the freon.

[Rick O]

Hey Scott,

I'm concerned that someone not properly trained is working on their own AC. Be very careful. There are two immediate dangers in working on your AC. One is frostbite from your skin coming in contact with liquid refrigerant and the other is from electrical shock. I know you're an industrial mechanic so I assume you know how to take all of the neccessary precautions with regard to electricity. As for the refrigerant, if you do decide to do anything on your own, be sure to wear safety glasses and neoprene lined gloves.

As for your problem: 51psig on the low side means that your coil is operating at approximately 27 degrees F. Any condensation that forms on the coil will quickly freeze. This problem becomes worse the longer the system runs until the air flow through the coil is blocked. If there is sufficient air flow past the coil then it most likely is low on refrigerant. But there are other considerations (sufficient ductwork for the system size, properly matched coil and condenser, clean evaporator coil, returns are open, etc). The only thing that I would recommend that you do is to feel the suction line entering the condenser. This is the larger of the two copper pipes and should have foam insulation around it. Cut back some of the insulation and feel the copper line. It should be cold and sweaty. If it is cold and sweaty and the suction pressure is still around 51psig then most likely you have an air flow problem. If it's dry and warm (ambient) then it's probably low on refrigerant.

HTH. Let me know.

Rick

[hesaias]

Thanks !
I came home today, to find the evaporator coil frozen, again, and the house at a toasty 85f. Ive had the lights on my tanks off for 2 days, both running fans only, so the reefs ore ok.
So I climbed into the attic, its only 150f up there:eek1: , and cleaned the evaporator coil. I dont think I did a real good job, i.e. its not plumb clean, but its some clean:D. After the cleaning, I noticed, the inlet duct was dropped down and sucking attic air in with the house air on the return side. After a duct repair, and sealing it back up, the cool air coming from the unit is 60.1F, the house is 76.7f now. The test comes around 1-3pm tomorrow. The temp rose 20 degrees in 3 hours today. I also bought some fin combs to straighten the condenser fins, wont that be fun:rolleyes: They arent in real bad shape, but Id like to fix it all whilst Im a fixin'
Rick,
thanks for the warnings:) Yeah, I wore gloves when I put the guages on and took them off, and Im not gonna attempt any real serious stuff, I just wanna fix what I can, and eleminate the chance of a yahoo HVAC man taking me to the cleaners:D
Hey KAS
I checked the drain line yesteday, no spooge to be found.

Again, thanks for all the tips guys, I really appreciate it:)

[Rick O]

Hey Scott,

How's the AC?

Rick

[hesaias]

Well, after I got up yesterday and the evaporator coil was frozen again, I called a HVAC guy, and he added a shot of R-22. Ill know for sure this PM when I get home, but the low pressure line was cool and sweaty last night.
Thanks for asking:D