A/C Freon

Old 07-02-02, 04:40 PM
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Question A/C Freon

My ac is not quite cooling as well as I would like it too. We just got hit with a heat wave of 95+ heat. Now last year I had no problem staying cool in this kind of weather but this year not so much. I am an automotive ac tech certified in r-12, r-22 and r-134a and would like to do a performance check on the system. Just about to change the filter and check the coils for debris (evaporator to me). I was wondering what type of refridgerant would be used. My unit is a 12 year old carrier/updraft furnace combo. I was also wondering what the pressures should be on the discharge and inlet side. Any help would be appreciated!
Old 07-02-02, 05:18 PM
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Your high side should read about 30 degrees above the ambient temp (saturation temp)- high efficeint units about 20 degrees. Your low side should read about 70psi if your inside temp is around 75 degrees. You want to keep about a 40 degree coil temp (saturation temp). So, your pressures should read about 250psi high side and 70 to 75psi low side if it is 90 degrees outside and your inside temp is around 75 degrees. Superheat, subcooling, is your best bet but that`s another story. These are just ballpark figures so don`t take them to the bank.

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