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Started By
Message
Is AC unit short cycling?
Posted on 7/5/24 at 5:39 pm
Posted on 7/5/24 at 5:39 pm
Hey everyone,
I got a new AC unit 6 months ago. House is about 40 years old and is insulated but no telling how old the insulation is. I live in about a 1200 SQ FT house in Louisiana. Currently, I have soffit vents around the perimeter and a whirlybird pushing the air out. One weird thing I have noticed is that my AC seems to run a lot. However, I don’t know if this is just due to being in the south. Currently, is 91 degrees out and I have my AC set to 74. It just shut off for 11 minutes and then kicked back on. However, at night when I put it to 69 and it’s about 82 out, it only shuts off for about 5-6 minutes at a time. Also have no clue if this is bad for the system itself.
I got a new AC unit 6 months ago. House is about 40 years old and is insulated but no telling how old the insulation is. I live in about a 1200 SQ FT house in Louisiana. Currently, I have soffit vents around the perimeter and a whirlybird pushing the air out. One weird thing I have noticed is that my AC seems to run a lot. However, I don’t know if this is just due to being in the south. Currently, is 91 degrees out and I have my AC set to 74. It just shut off for 11 minutes and then kicked back on. However, at night when I put it to 69 and it’s about 82 out, it only shuts off for about 5-6 minutes at a time. Also have no clue if this is bad for the system itself.
11
Posted on 7/5/24 at 5:43 pm to sctiger07
Do you see water in the drip pan?
Posted on 7/5/24 at 5:45 pm to Major Dutch Schaefer
No water in the drip pan.
Posted on 7/5/24 at 5:46 pm to sctiger07
Same happened to mine. Drain line was clogged.
Posted on 7/5/24 at 5:46 pm to sctiger07
Seems normal
Posted on 7/5/24 at 5:59 pm to sctiger07
It's going to run a lot when it is 95-100 outside. When you try to go from 74 to 69 a good running unit can only drop a degree roughly every half hour so it will run continuous for 2-3 hours to get to 69.
Depends on how leaky the house is, who sized the unit, etc.
As far as attic ventilation goes check the soffit vents, they typically have a bug screen and it gets clogged with dirt over time to where the vents are essentially blocked. You'll have to unscrew the grilles to do this.
BTW "short cycling" means it is not running enough IE an oversized unit that satisfies setpoint too quickly but doesn't dehumidify well because it doesn't run long enough.
The A/C will have to run longer to maintain a lower setpoint, even well into the night as everything is heated up even though the sun goes down.
How often are you changing your air filters? Don't use those ultra high efficiency ones.
Depends on how leaky the house is, who sized the unit, etc.
As far as attic ventilation goes check the soffit vents, they typically have a bug screen and it gets clogged with dirt over time to where the vents are essentially blocked. You'll have to unscrew the grilles to do this.
BTW "short cycling" means it is not running enough IE an oversized unit that satisfies setpoint too quickly but doesn't dehumidify well because it doesn't run long enough.
The A/C will have to run longer to maintain a lower setpoint, even well into the night as everything is heated up even though the sun goes down.
How often are you changing your air filters? Don't use those ultra high efficiency ones.
Posted on 7/5/24 at 6:06 pm to AndyCBR
I replace my filters once every 2 months. I just want to make sure I don’t run this unit to the ground in a few years
Posted on 7/5/24 at 6:09 pm to sctiger07
What's your tonnage?
Posted on 7/5/24 at 6:12 pm to sctiger07
What’s the frequency, Kenneth?
Posted on 7/5/24 at 6:40 pm to sqerty
I think 2.5 tons. Can’t remember exactly. But I know when the guy who installed it did, he said he would absolutely make sure not to oversize me.
Posted on 7/5/24 at 6:49 pm to sctiger07
quote:
It just shut off for 11 minutes and then kicked back on
The amount of time that it is off is definitely related to how well the house is insulated. With the heat we are having 11 minutes doesn’t seem that bad
Posted on 7/5/24 at 8:02 pm to sctiger07
Set a water sprinkler up to spray on it and it will help it cool better
Posted on 7/5/24 at 8:18 pm to sctiger07
quote:
I got a new AC unit
Unit or system?
There are too many unknowns here. How bad is the insulation? Leaky windows and doors? Pier and beam home? Brick? Trees or in the middle of a field?
The system seems to get you down to your set temperature however your house isn't maintaining the desired temperature for a longer period because it's probably poorly insulated.
Oh, and replace the whirlybird with a power ventilator. Removes much more heat and moisture and doesn't rely on wind.
This post was edited on 7/5/24 at 8:29 pm
Posted on 7/5/24 at 8:23 pm to AndyCBR
quote:
BTW "short cycling" means it is not running enough IE an oversized unit that satisfies setpoint too quickly but doesn't dehumidify well because it doesn't run long enough.
This.
Had this problem on an old house I bought as a rental. The unit was old, but was also oversized. Way too much humidity being left in the house. The walls were sweating and there was little mold.pockets around the outlets where the humidity was turning to water on the walls. Replaced the whole unit with one that was properly sized and humidity issue gone.
Posted on 7/5/24 at 8:37 pm to sctiger07
What you describe is definitely not short cycling. If anything with your unit, the tolerances on your thermostat may be a little tight.
Also, be sure there are not some air leaks right around your thermostat causing it to read incorrectly. Mainly, ensure that the hole around the wires that wires that go into your thermostat is sealed up. You don’t want a false reading because unconditioned air is leaking from your attic.
Also, be sure there are not some air leaks right around your thermostat causing it to read incorrectly. Mainly, ensure that the hole around the wires that wires that go into your thermostat is sealed up. You don’t want a false reading because unconditioned air is leaking from your attic.
Posted on 7/5/24 at 9:29 pm to sctiger07
quote:
I replace my filters once every 2 months. I just want to make sure I don’t run this unit to the ground in a few years
Good on the filters then.
If you live in the South and want to experience 74 degrees during the day and 69 at night, the unit will have to run a lot. Probably 2/3 of the 24 hr period will be with the A/C running. This is typical in the heat of summer.
The fact that you are able to achieve setpoint at 74 is a good thing. If the unit is able to achieve the 69 setpoint at night, even better.
Now, if you said the unit runs continuously all night and doesn't shut off, then something is wrong.
And BTW it doesn't matter what kind of attic exhaust you have if the soffit intake vents are clogged. No air in=no air out.
Posted on 7/5/24 at 9:31 pm to sctiger07
quote:Mingo-like comment here.
But I know when the guy who installed it did, he said he would absolutely make sure not to oversize me.
(alter???)
Posted on 7/6/24 at 11:10 am to sctiger07
quote:
BTW "short cycling" means it is not running enough IE an oversized unit that satisfies setpoint too quickly but doesn't dehumidify well because it doesn't run long enough.
This - HVACs, like autos, are designed and built to run “continuously” - they don’t need to “rest”.
Frequent short-cycling (stopping & starting), usually associated with an over-sized system, will significantly shorten the life of a HVAC compared to a properly sized HVAC that runs long hours during the hottest days of the year.
Posted on 7/7/24 at 1:05 am to sctiger07
Sounds normal for our recent heat/humidity.
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