How Long should my A/C Run

I have been getting questions from customers asking “How long should my A/C Unit run to cool off my house?” The answer varies during different times of the year. With the record heat we have been having lately it should run a long time. Design conditions for Corpus Christi are 76 degrees inside at 95 degrees outside. That means if your air conditioner is sized according to design whenever it is 95 outside and you have your thermostat set at 76 the unit will run 100% of the time. On the average we have 4 hours a year over 94 degrees in Corpus Christi. This year we have totally blown that average away. We have had multiple days in June and July this year where we exceeded the annual average in just one day. This has put a burden on our air conditioners and if the system is sized properly then the temperature in the space will rise during the heat of the day and then come back down late at night. The normal differential is about 20 to 22 degrees, so if the temperature outside gets up to 100 then it may get to 78 to 80 in the space. If your system is maintaining 75 or 76 degrees on these extremely hot days and is even cycling off any time between about noon and 8pm then your system is oversized. The big disadvantage to being oversized is when it is not peak season the system will short cycle more. Short cycling of the system reduces the humidity control in the space and also greatly reduces the efficiency. The AC-Enhancer can help minimize some of the short cycling disadvantages but it is still better to have a properly sized system. See my previous tip about Bigger is NOT Better. It is Much Cheaper to run a smaller unit longer than it is to run a bigger unit shorter. So if your unit is running a lot and maybe not even quite keeping up during the heat of the day, that is normal for the extreme heat conditions we have been having.

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