Central Air Condition Charge

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Old 10-14-03, 03:50 PM
bobwhite1
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Central Air Condition Charge

I have a 3.5 ton Central Air Conditioner and I'm getting different answers as to the required charge of R22. I'm told the low side should read 70 lbs on the outer gage reading. I'm also told it should read 32 % on the R22 reading on the gage. Both answers have come from Air Condition service people. I know when using R12 on car units you read between 28 and 32 %. What do you suggest? Bob
 
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Old 10-14-03, 05:37 PM
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AC

Get the paper that said that you are EPA then you would know what the Psi is for R22, R12, R13,R502,,R717,R410a. ED
 
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Old 10-14-03, 05:58 PM
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pressures

are dependant on several things, wet bulb entering, dry ulb entering, superheat, etc. i am with ed, get a pro out there.
 
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Old 10-14-03, 08:34 PM
bobwhite1
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I appreciate your concern about the epa certification Ed, but after having 2 EPA certified "PRO's" come out and check the unit for a leak and finding none, I found it myself. I didn't guess or have a electronic detector just an old butane and copper flame detector. First pro said the leak was so small it couldn't be found but not to worry about it. I wouldn't take much to charge it about every 2 years or so. In one month it was low again. Could never get him to come again. His price for cleaning the Evaporator and condenser $200.00. I wasn't home for Pro 2, he couldn't find the leak and told my wife it was a old unit and you could expect some small leaks and some evaperation. He charged the unit and my wife $120.00. doesn't evaperation sound strange to you Ed? Years ago I learned in automotive air conditioner class that evaperation doesn't take place only leaks can cause lose of freon. I found the leak in the low side shrader valve. I changed the valve and have the R22 to recharge the unit. I've had the tank for about 10 years and it is still at the same amount it's been for years. Now I have my own gages and all I want to do is find out the low side reading for R22 in a central air unit for maximum cooling. If no one can tell me I guess I can check another unit i have that is working well. I think after paying out $320.00 for the something so simple and having to find the problem my self you can understand why I don't want to put out any more money. If some one here can help great. if not I thank you anyway. Bob
 
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Old 10-15-03, 05:39 AM
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At least you are polite. Most people that don't get directions to handle refrigerant because they are not certified get bent out of shape. We can understand your feelings and any good tech should have found the leak.

You cannot go on just pressure to charge the unit properly like a car. Since you've fixed the leak get a friend or relative to recomend a good tech.

P.S. Telling you it evaporated is garbage. It only leaks or gets huffed.
 
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Old 10-15-03, 08:56 AM
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AC cost

Sorry there BOB. We do have a lot of fly by night techs out there.It evaporated thats good. like I had one gal tell me she needed freon gas. I ask why and she said that she had used it all up. That the tech that had been working on it for years told her he had to fill it up each year so she had enough for all summer. Just like they have to fill here LP tank.
If you didnt have the tool to work on that schrader,and all the freon is out ,leak on low side .You should also have some one vacuum the unit and put in a new drier. ED
 
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Old 10-29-03, 10:56 PM
binford
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a/c

Read the label on the unit. most units will say how much they hold. it might say 127 oz. or 9.9 lbs.
You can use the pressure you suggested, and it will be close.
you can take the epa test online for $19.95, but it does not cover how to determine superheat or the proper charge. Just the proper handling of refrigerants and the fines for releasing it.
 
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Old 10-29-03, 11:23 PM
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You might want just a little more R22 in the system if you are running 70 psig on the low side. That pressure corresponds to an evaporator temperature of about 30 degF. You could get some freezing on the evap coils. I would add just enough R22 to get the low side up to about 75 psig after the house is good & cool and your A/C has been running for a while. I have a 3.5 ton unit in my house and it takes about 7 and a half pounds of R22.
 
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Old 10-30-03, 02:02 PM
bobwhite1
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central air condition charge

Thanks to all the info received. I also had terrible distribution of air, both heat and cooling. The setup in a double wide is terrible if you have two separete units. Air distribution from the A/C would lose through the heater unit and visa versa. To correct it once and for all I redisigned the duct system. I completely sealed off the old duct system and installed a new one. I installed a 3'x4' distribution box centered between the A/C at one end of the house and the heater unit. I ran a 12" flex duct from each of the units, and a one way flue on each side where the duct connected to the distribution box. This prevents loss of distribution when one or the other unit is in use. I used 6" duct to each outlet in the house trying to keep all lines equal. It took my son and myself about 3.5 hours to install at a cost for material of $360.00. The results are fantastic, the vents have to be partially closed, whereas in the past some of them had very little output. Everything is working fine now and the difference in the electric bill went down substantually enough to lead me to believe my investment will be returned in about 6 months. Once again thanks to all that replied. Now if I can find someone knowledgeable in eradicating roaches (lol), Bob
 
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Old 10-30-03, 05:37 PM
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what is the suction pressure?
 
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Old 11-01-03, 07:29 AM
binford
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pest?

Are you for real on the bugs. when I lived overseas, the only way to control them was to use boric acid. I would sprinkle it behind kitchen items and even had a bowl next to the frig. where I mixed it with bacon grease. You can buy it at home depot in the garden area. Back them it was only found at the pharmacy, It's used as an eye wash.
 
 

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