air conditioning

Old 09-16-02, 02:33 PM
Greg LaSalle
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air conditioning

I have two central air conditioning units, one for downstairs and one for upstairs. The house is about 9 months old. Both units are mounted on "pads" in the back yard. The separation between the two units is approximately 6 inches. Recently I have noticed that when the temperature outside is 100 degress or more (I live in Southern California), the upstairs temperature, which is set at 78 degrees, climbs to 80 to 83 degrees, and the unit runs all day long. I am concerned that the capacity of the units may not be sufficient, that the units are too close together and air flow is therefore restricted, they may not have sufficient freon, they are poor quality unites, etc. Is there any source of information that may help me find out what if anything is wrong. I believe that the builder indicated that the units should be able to easily keep the internal temperature at least 30 degrees less that the temperature outside. The downstairs unit seems to be able to hold the temperature at 78 degrees, even when the temperature outside was 116 degrees. I know that the attic area gets hot, but I would like to think that because the house is new, the builder has used sufficient insulation.
Old 09-16-02, 04:07 PM
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the way to see if the units are functioning up to spec is to determine the temp drop at the blower unit itself. you should have 16 to 20 degree drop. by checking at the register, you would get thrown off, especially on the one in the attic where i assume the duct runs. MINIMUM clearance on all sides of an outdoor unit is 18 inches, check your owners manual. what brand?
Old 09-16-02, 07:23 PM
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Since your home is new, have the builder get the installing hvac company to check the systems. You should be under warrenty for at least one year by the installer.
Also keep this in mind. All R-22 a/c systems only have a true capacity rating till a 95d outdoor temp. Above that you lose capacity. A 116d outdoor temp and your second floor keeping 83d temp sounds pretty normal. That's a 23d drop from outdoor to indoor.
Old 09-16-02, 08:20 PM
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When air conditioning systems are designed, an outdoor design temp is used that ignores the hottest times by 2-1/2%. If systems were sized for the maximum load, then they would be oversized most of the time which is inefficient and provides poor comfort. I was able to find two locations with established outdoor design temps close to Valencia. The Summer design temp for Los Angeles is 89 and for Santa Paula is 86. Looking at the map suggests that you might be in a hot valley? On a 116 day, the upstairs temp at 80 to 83 is a 36 to 33 degree temperature difference which sounds like what you were told.

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