My air conditioner is able to cool the house down from 7pm until around Noon the next day. Then it begins to struggle to keep up. I have it set at 74. Right now its 77 in my house(2pm). It will usually get to 78 or 79 before it is able to start catching back up. Not unbearable and it cools at night so I'm able to sleep comfortably. I know its really hot outside and I would expect a degree or two above what its set at for a few hours in the heat of the day, but right now its more like 5 or 6. Two years ago this started happening. I added more insulation in the attic and that has helped keep it a few degrees cooler, but I'm a bit perplexed as to what could be causing this. Anyone had a similar issue?

Probably a touch low on Freon.

Finally found my temp gun. I'm getting an average of 76 at the vents and 77 at the return. Its definitely isn't working right which I guess I already knew. Working to get someone out now.

Does shading your A/C unit make that much difference?

I had the same issue and it was dirty coils.

Slab or pier and beam?

Could be Freon or bad expansion valve.

Slab

You should be getting about a 20 degree drop out to the vents. I would have the freon level checked sounds like it is low. You can also go outside look at the big line on the unit and see it it is sweating like a cold beer can sitting outside. If it is not, you are low. That line should be sweating like crazy in this heat and humidity.

RCR06 said:

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Finally found my temp gun. I'm getting an average of 76 at the vents and 77 at the return. Its definitely isn't working right which I guess I already knew. Working to get someone out now.

Does shading your A/C unit make that much difference?

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You need an actual thermometer in the vent. 76 at the vents doesn't make any sense unless your system is straight up broken. If you're at 77 at the return, you should be at 57-61 at the vents, and hopefully closer to 57. If you're truly pushing 76 at the vents, I have no idea how you're keeping the house at 80. Seems like you'd be lucky to get it down to 85 or 90. A meat thermometer with a probe would be a better choice of you don't have an A/C thermometer..

I will say, though, on a decent day in the 80's or low 90's, I get a delta t of 18 degrees. When it's 105 outside, I'm looking at 15.5. When it's this hot, your A/C is not only fighting temp gain in the house, it's fighting a smaller delta t outside. It can't move as much heat because there's less room for it in the air outside. It's harder for heat to dissipate from the coils into 105 degree air than 90 degree air.

ETA Shading the outside unit probably won't make a drastic difference, but it helps. Just don't impede air flow at all. The idea is to keep the A/C in the coolest spot you can. Again, heat tries to reach equilibrium, so you can move a lot more heat into a cooler space than a hot one.

ETA #2 You need a a lot of shade. A/C's push a large volume of air, so you need a lot of air around the unit to be cool. A shady backyard will keep a lot of the air your A/C will suck in at ground level much cooler than an open yard. Shading just the unit limits the heat gain from direct sun, but the majority of heat is being dumped into the air. Cooling the air with large shade trees did much more than shagging just the unit. Shading the unit gives marginal returns, though with Texas gets a lot harsher sun than most other places in the US and likely isn't a bad idea as long as you maintain air flow.

Well, I was low on freon(whatever the new coolant is). They topped it off(4 pounds) and its cooling much better now. When its extremely hot outside like it was early last week I understand it may not be able to keep up to exactly what its set at, but it should be closer than what it was.