I have a new outside unit (one year old) and a new coil (brand spanking new) on my central air conditioning. We have had lots of troubles but things to be working okay for now. The only thing is, no matter what we set the thermostat on (usually around 75), the AC won't keep the house that cool. It will creep up to around 78/79 on really hot days. We live in Texas where the temp has reached as high as 107 degrees. So to be clear, the thermostat is set on 75, but the temperature in our house is 78.

Our AC repairman tells us this is normal because we live in a manufactured home with a metal roof. Is he telling us the truth or does he just not want to keep working on our system, which is still under warranty?

He is telling you the truth.

I'm sure your unit is running constantly, trying to keep up, but just can't compete with the heat and the lack of good insulation in the roof and walls of the manufactured home.

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Originally Posted by progunr

He is telling you the truth.

I'm sure your unit is running constantly, trying to keep up, but just can't compete with the heat and the lack of good insulation in the roof and walls of the manufactured home.

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Thank you for the reply. :)

We have a hard time trusting our AC guy. I think that's because we have had so many problems (the latest when a couple of weeks ago they replaced the coil and didn't get the "pressures" right so on Saturday when they don't answer the phone or do service calls, our AC royally messed up when it was over 100 outside. We were HOT both physically and emotionally!). He is a nice guy but nice doesn't keep us cool.

You're right, it runs constantly during the day. At night it does cycle on and off and seems to work like a charm. I can't wait for fall!

Well, it might not be sized correctly. e.g. the metal roof wasn't considered.
Was a manual J calculation done for the house? This is he correct way of sizing an AC or heating unit.

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Originally Posted by KeepItSimpleStupid

Well, it might not be sized correctly. e.g. the metal roof wasn't considered.
Was a manual J calculation done for the house? This is he correct way of sizing an AC or heating unit.

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I have no idea how it was calculated. The unit is the same size as the original one that was installed when we got our house. Last year is when we started noticing that the temp would get higher than what we had the thermostat set on, and last year is when we got a new digital thermostat. So it may be that we always had this situation but just weren't aware of it. My husband says the AC used to work a lot better but I think it has just been a lot hotter the past couple of summers.

It is possible that the unit is too small. It was part of the deal when we bought the home, and I'm sure those dealers try to get out as cheaply as possible.

You can do it using a program from here: HVAC-Calc HVAC Software The Heat Loss Calculator HVAC, HVAC/R, HVA

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Originally Posted by KeepItSimpleStupid

You can do it using a program from here: HVAC-Calc HVAC Software The Heat Loss Calculator HVAC, HVAC/R, HVA

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Thanks for the link. :o)

I will download that free trial.

I am having the same issue. We live in Houston, Texas and right at 5:00 the displayed temp will say 79, but the set temp is 76. Our master bedroom upstairs is nice and cool, but the other two bedrooms are ridiculously hot. Did you figure out what the issue was with your A/C?