AC Runs Nonstop

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Old 05-27-14, 07:31 AM
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AC Runs Nonstop

My air conditioner runs nonstop when set below a temperature that it seems to deem too low.

For example, if I were to set the desired temperature anything below 76 degrees - say 74 - the unit will continuously run and MIGHT get to 74, but even then the unit will continue to run while the desired temperature and actual temperature match. The only way to stop it is to manually turn the temperature up.

The short story is that I have no control over how low I want the temperature to be. It usually tops out around 75 and still continues to run. My understanding of air conditioning is: you set the desired temperature; the unit runs until that temperature has been met; the air conditioner turns off until the actual temperature goes above the desired temperature.

My landlord has sent contract repair men twice now and they claim there is nothing wrong, though the problem persists.

I don't want the temperature in the apartment to be ridiculously low; I just want the option to set it below 75 and I especially don't want the unit to run 24/7 with only moderate effectiveness, which essentially the case now.

I have changed the filter and ensure it was secure. I also replaced the existing thermostat with a new, digital model, hoping that the original thermostat was the issue.

Thanks!
 
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Old 05-27-14, 09:33 AM
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Try to get a delta-T number first. if it is more than 15 degrees, your AC is OK, and you may have other problems. Delta -T is the difference between room temperature and the cold air temperature comes out of the AC register. and also the cold air must be strong enough so you can feel it from 8-10 feet away.
 
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Old 05-27-14, 09:48 AM
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Welcome to the forums.

Thermostats don't always activate at the exact temperature they are set for. Also.... the thermostat will read out 74 but it actually runs in tenths. 74.1, 74.2 - 74.9. So while it only says 74 it could technically be above it.

Normally you can expect the A/C to shut off when it reaches 1 degree below what it's set for.

Your A/C system may not lower the room temperature to where you set it for. Like clocert mentioned it depends on outside air temperature for how low the inside temperature will go.
 
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Old 05-27-14, 09:57 AM
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Be careful with Delta-t; if the airflow isn't correct or it's really humid inside, the reading doesn't mean much - you could have a 25F+ delta-t but poor performance. (you could have a 10F split and plenty of capacity of the fan speed is set far too high)
 
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Old 05-27-14, 10:20 AM
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AC Runs Nonstop

Thanks for the prompt replies, guys.

So it possible that the AC is functioning correctly but that the humidity from outside may be seeping in and counteracting the AC?

I live in central Ohio where humidity runs between "50% (mildly humid) to 92% (very humid)", according to weatherspark.com. I can safely say that between June-September we are closer to that 92% mark than the 50% (at least it feels that way). Needless to say, it gets uncomfortably humid here.

I do live in an older apartment with plenty opportunities for outside air to seep in through the windows and doors, especially in the living room where the thermostat is located (it's a small room). We are also sandwiched between the two other apartments in building, which I think helps in the winter when it's cold but could definitely be a curse when it gets hot.

Thanks, again.
 

Last edited by landops; 05-27-14 at 10:45 AM.
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Old 05-27-14, 05:32 PM
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Yup.

Humidity cuts actual cooling capacity -> pulling moisture out of the indoor air can eat up 1/3 or more of cooling capacity. The more moisture there is, the greater the effect.

In an old rental apartment I wouldn't be surprised if the ductwork isn't great, the indoor unit isn't matched to the outdoor unit, and the system isn't running at rated capacity.
 
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