Hello I'm not very good with ac units. I just bought a house. The ac has been working great but randomly around 4-5 pm every day the ac unit won't stay at my set temperature but within an hour it catches up and is fine until next day. I live in Florida so this makes no sense for it to struggle at this time when at 12pm it's the hottest and it's super cool and nice in my house. I have it set at 78 and during the 4-5pm it's 80-81 but it's not everyday. It's the weirdest thing ever. It's also a non programmable thermostat. Any ideas?

 

Is your AC unit controlled by the power company? Some people sign up to allow the power company to turn them off during peak usage times.

 

I'm not sure. I know they offer that but I never applied for it. The thing is though it runs during this time.

 

You need to find out if the compressor is running while inside temperature is above the set point. Easy check: Hand feel the large pipe at near the outside unit when you have this problem, If it feels cold, the compressor is running, if not, the compressor is not running.

 

And what does this mean if it's not? It hasn't done it yet today. It usually does it around this time if it does do it.

 

It is above set point and it's cold. Only by a degree today. It did it around 430. It's not terrible or anything it just makes me wonder why all day during peak heat hours it's fine but as soon as it's 4-5 it gets higher.

 

You also need to record the incoming cold air from register inside the house. The cold air temperature must be at least 16 degrees lower then your room temperature, and the incoming air has to be strong. At the same time, the outside pipe must be cold (I mean real cold, feels like a glass of ice water). I thought the peak heat hours of the day is between 3-4pm. So it is reasonable that your AC has problem around 4pm.

 

Yeah I'll check it tomorrow with the temp gun from work.

 

The power company only cuts power to your appliances when demand is high so it's not a time of day thing.

 

Yeah but if they cut the power wouldn't the unit outside not be on at all?

 

Yes.... that is correct.

Your problem sounds more like a sun thru the windows issue..... not an equipment malfunction.

 

And one thing I didn't see mentioned...you have to remember that the insulation and construction of the house reduces the amount of heat to the inside. So at the hottest times of the day it will take a while for the heat to work itself in. It won't stop until outside cools off enough for the heat in the structure to be radiated back to the outside.

According to your local news...the hottest part of the day is going from about 1 to 4, peaking around 2. That's if you don't get any big thunderstorms of course. And as mentioned, just because that's the warmest part of the day outside, it doesn't necessarily mean that's when the biggest heat load is on the home. Windows, doors, garage, roof exposure...all make a difference.

My place in VA had a similar situation...if I didn't set the day temp low enough or early enough (because I was working), when I came home at 430-5 it would run until 9-10pm to cool it off.
Guy came out and told me just lower your temp 2 degrees on the setback and start it back at your normal temp an hour earlier. Voila! No more coming home to a hot house. And my bill dropped a few bucks (barely noticeable, but it did).

 

Yes this sounds correct. I also come home at this time and open my shades to sliding glass door. I just thought maybe my ac was ready to take a dump. I just bought the house so it was a worry of mine.