Posted: 10/8/2006 8:03:53 AM EDT
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Is an air conditioner more efficient if it cools ambient air at about 45% relative humidity or if it cools a moist air mixture at about 80% relative humdity? With the moist air mixture, the air should be saturated (relative humiditiy is 100%) when it leaves, but the specific humiditiy has decreased. Specific humidity remains the same when cooling of the ambient air as no condensate drips out of the bottom of the AC unit. Also, why is one more efficent than the other from an enthalpy standpoint? Scott |
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Dear god... I have been in the trade 10 years and I don't know where to start on this question. A/C has to first lower the humidity levels to achieve a comfort level most owners want. You want to avoid the "cave cooling" effect where the temp stays low but the humidity is high, it is uncomfortable and undesired. Oversizing a A/C system will cause this effect. As for your question: It would make zero sense to add humidity to the airstream when you are trying (or the A/C is trying) to remove humidity. Essentially it is a whole house dehumidifier. On a humid day it has the capability to remove upwards of a gallon+ an hour. Hope this helps.  ETA - Humidity levels inside will not matter to the A/C. Higher outdoor temps will cause strain on the compressor, longer cycles, and more energy draw. Rain helps by getting the condenser coil wet and aiding in heat transfer. |
I realize you don't intentionally pump moisture into the air stream. I guess my intial question was worded poorly. I'm asking about if you run humid Florida air through the AC rather than dry Arizona air through it, but both flows are the same temperature. |
Ahhh... Ok, I have a better understanding. Like I said before, indoor humidity levels don't much matter to the A/C, it is basically a dumb hunk of metal and motors that run when a thermostat tells it to. You have to properly size the A/C to provide adequate dehumidification, oversizing and you get "cave cooling", under sizing and you get poor dehumidification and it never keeps up on a hot day. Now that being said, they have come out with t-stats that can measure and control indoor humidity levels using the A/C as a dehumidifier by controlling indoor blower speeds and length of cycles. You set the indoor humidity at 50% and the A/C cycles as necessary to hold that percentage. Outdoor humidity and temps are what affect the efficiency of a air conditioner. |