AC question and the Logic that was explained to me

[Hotflorida]

I moved into a 1978 Modular home(1000 sq ft) with a brandy new 3 ton ac. I set the thermostat at 78. Without changing the thermo., the temperature goes from 78 degrees in the early a.m, to 84/85. It was explained to me, that because this is an older Modular, with little or no insulation, that in the heat of the day, 84/85 is the best this unit can do. That being said, if the little 3 ton is working to keep up, why doesn't it come on more often than it does? One would think, the (big) electricity beast would just keep running. The wall theromstat is not digital. However, I have two digital therometers which read the same, 84/85 in the afternoon, but the outside thing just kicks on now and then. Thank you for reading and hoping you can provide an explanation I can understand......

[rmurray]

Most properly sized a/c units will keep the home about 20 degrees cooler then the outside temp....I do not know where you are but here in Augusta, GA we just had out 21st day over 100...

Your 1978 model home is built to the modern HUD code..The insulation requirements were the same then as now...There is an adjustment in the thermostat that sets the limits of when the unit goes on and off..Most are factory set at a 2 to 3 degree spread...on at 81 off at 78..I have mine set to 1 degree...I find it more comfortable...The unit should run a majority of the time in this time of the year...This will keep the humidity down..Yoou may need a new thermostat..

[Hotflorida]

Thank you for the info.