# AC is running...but it's cooler than my set temp??



## BlueWaveCapt (Jan 8, 2007)

The AC control in my house might be messed up...I don't know.
I have it set on 78*...and even when the thermostat says it is 76* in the house the system will still be running. It will stop running eventually, but I thought it was supposed to stop when it dropped at or below my set temp.

More details...2 units (1 large and 1 small).
Large unit is for the main house and upstairs gameroom/bonus-room. This unit is zoned. There is a control upstairs (set always on 81*) and control downstairs in the living room for the main house and spare bedrooms (this is the control that I think is messed up). 
Small unit is for the Master bedroom/suite - leave it set on 76-77* and it seems to function properly. 

Do I have something jacked up with that main controller for the big unit?


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## Africanut (Jan 15, 2008)

Check and see what the deadband setting is at --some of the upper end stats have it as an option instead of the factory default of +or- .5 degree. If it is set at say a 2 then it will swing 1 degree both sides of the set temp before cycle of or on. On the coast it is not uncommon for the Differential or deadband to be set at 2 or more because the longer cycle times help pull the higher humidity out and increase the delta value on the e-coil. Dirty little secret that a/c companies don't want known is that increased deadband results in less wear and tear on compressors and less breakdowns.


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## tbone2374 (Feb 27, 2010)

I'm no expert, but that sounds like a simple thermostat problem. Maybe I didn't get the full jest of your problem.


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## sea ray (Mar 15, 2006)

check to see if the FAN setting is set to ON instead AUTO. This will cause the fan to run all the time instead of cutting on and off with the compressor. It is an optional setting


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## BlueWaveCapt (Jan 8, 2007)

It is set to AUTO.
I've lived in this house almost 3 years and this has never happened before. Just started about a week ago out of the blue. It used to just cycle "off" after it reached the desired temp setting, but now...it keeps running down to 76* when I have it set on 78-79*.

I have no idea how to check the "deadband" settings.


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## Mont (Nov 17, 1998)

It's got too much freon, that's why it's getting too cold. 
You need to let some out and it will be fine.

JK!

Replace or have someone replace the thermostat.



> Differential or deadband to be set at 2 or more because the longer cycle times help pull the higher humidity out and increase the delta value on the e-coil. Dirty little secret that a/c companies don't want known is that increased deadband results in less wear and tear on compressors and less breakdowns.


Interesting concept. The more it runs, the longer it lasts. Hmm. That must be one unique machine. Kinda reminds me of the infinity bird my Dad used to have and tell me about. He lost it when it flied at ever increasing speed and ever decreasing circles and flew up its own ***. We never saw it again.


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## essayons75 (May 15, 2006)

That's funny Mont! I'll take the extra freon.

Now, I have a dumb serious question.

Came home from vacation this week, put A/C on 82 before leaving, and it had a hard time getting back to 80 (hot late afternoon). It ran for about 4 hours straight until I cut it off to give it a 10 minute break. I put a water sprinkler barely running on the outside fan/compressor unit and turned A/C back on. Cooled much quicker and turned off.

I figure 3 things could have helped.

1. Turning off the unit let something defrost.
2. Sprinkler helped efficiency.
3. Outside heat cooled enough to let unit catch-up.

Or a combination. I mostly want to know if #2 is worth the cost of water used?

Unit is fairly new.


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## Mont (Nov 17, 1998)

The sprinkler just helped it out a bit. I wouldn't do that on any regular basis though, it's very hard on the outdoor coils. A/C systems generally won't recover from a setup/setback temperature during the heat of the day. At 95 degrees, it's supposed to run constantly to maintain 75 degrees inside, so starting it late on a hot day will delay it getting down to temperature. Honestly, with the outside temps we have currently, you are probably better off using no more than 2 or 3 degrees of setback, if that much. Once we get into September and beyond, you can use 5 or 10 or whatever you normally use. It's been unreal hot lately. Vacation is different (longer than 24 hours), but just be aware that what you found happening is probably perfectly normal in this heat.


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## FishinFoolFaron (Feb 11, 2009)

Ty, the answer is all of the above. Did you get it serviced yet?
Ask you brother how well a clean unit works. hee hee

As far as if its worth the water used, was it worth it to you to get cooled down?

If you're going to do this out of town thing on a regular basis, I can set you up with a thermostat you can control by phone.


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## essayons75 (May 15, 2006)

Thanks gentlemen. I guess I should forgo the Houston water sprinkler at $4.00 a gallon especially if it could harm the unit.

No, haven't serviced the unit, but did replace my big filter. Brother is very happy with new unit and other unit serviced. Can you program my wife and sons to adjust the thermostat from 75 in the morning to 80 in the afternoon while I am out of town?


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## BlueWaveCapt (Jan 8, 2007)

Mont said:


> Replace or have someone replace the thermostat.


Okay I'll do that this weekend then. Thanks Mont!!


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## TheSamarai (Jan 20, 2005)

I had one rite brand thermostat and it was doing the same thing. Changed to a honeywell and my problem was solved.


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