Short cycle ac concern

HU-597194232

last year

last modified: last year

We had a heil ac installed within the week. House is 2500 square feet with 800 square foot basement. Ac is 3.5 ton. Temps have been mild 75-80. Ac runs about every 10 minutes but for short cycles 5-8 minutes, 3-5 later nite. Hvac installer said that is due to mild Temps and would resolve in warmer weather. Does that sound accurate

Comments (10)

klem1
last year
If house stays comfortable,don't worry bout it.
PRO
Charles Ross Homes
last year
"Hvac installer said that is due to mild Temps and would resolve in warmer weather. Does that sound accurate"

I'll answer with a qualified "yes." When the difference between outdoor and indoor temperatures is only a couple of degrees there is little cooling load. When the cooling load is low, you should expect the air conditioner's run time to be reduced compared with that on days when the difference is more significant. That said, a concern with short cycling is the potential for high indoor relative humidity when there is little or no air conditioning called for and little dehumidification as a consequence.
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Good morning. I have no experience with A/C so all help much appreciated. Last week we had a power cut in the middle of the night. Since then I noticed a few issues with the A/C. Firstly the upstairs unit wouldn't power on without me going in to the attic and turning the power switch up there, the thermostat wouldn't control it. Then it worked fine for a few days. Last night it started going through short cycles, coming on for twenty seconds and going off repeatedly. Tonight I came home from work and it's running, thermostat won't shut it off. It's blowing cold air constantly..... I've taken the thermostat off to change batteries and a/c kept running and I still can't control it with new batteries in the Tstat. I can hear thermostat turning on and Off but fan is constant. The downstairs unit is working no problem (knock on wood) and we didn't have any other electrical problems after power outage / surge.... Thanks a lot!
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Is my AC short cycling?
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Comments (9)
The t-stat is in the master bedroom on the wall opposite where the ceiling supply vent is in the room (~8 feet apart) and directly beneath a small return vent. Additionally, it's next to the bedroom door going into the hallway where the main return vent is located. I'm not sure what the CFM is on the air handler but when the unit turns on there is a very noticeable "breeze" that can be felt around most vents and it's particularly noticeable in around the t-stat. We set the temp at 68F and leave it alone and there's not humidity control. The t-stat in the old system (where I didn't notice frequent cycling with this t-stat) was located in a hallway under a large return vent and with no supply vent anywhere near it - supply vents were in bedrooms only. The air felt the least conditioned here I guess because of the large return vent above the area. I feel like the nighttime cycling has to do with the t-stat's 1F tolerance combined with it's close proximity to a supply vent. In other words, outside air temp is 70F meaning not much cooling is needed but with the 1F temp tolerance it's enough to kick the system on only to produce a cold draft and very quickly drops the temp to 68F and kicks it off. It kicks on at again at 69F and off at 68F. That's why I was wondering if a t-stat that would allow me to adjust that to say 3F would be better? If set the t-stat at 68F it would take additional time for the temp to rise to 71F before the system turned on again.
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What constitutes short cycling??
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Comments (29)
"They hit 120 degrees a couple weeks ago. She has 2 AC's and said they didn't shut off all day." "Run-time varies from 30+ mins during heat of the day to 10-ish mins in early morn hrs" This varying equipment behavior is to be expected, isn't it? I would believe that a lot of people "set it and forget it" at their thermostat. I do. 73F from May to September, no setbacks programmed. With this in mind, how can one expect their system to do anything else but have cycle times of very different lengths? When does the thread topic change from "it's short cycling!" to "it runs 24/7!"? After all, isn't the purpose of HVAC to provide comfort? I'm comfortable at 73F. If I were to have a bigger droop set in the stat, or agree to raise or lower the set point as outside conditions change, I guess I would have uniform, perfectly long cycles. No thanks, I'll leave it as is. Comfort does come at a price sometimes.
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Compressor is short cycling.
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What Is Air Conditioner Short Cycling? https://www.centralacwarehouse.com/ While the average air conditioning cycle lasts around 20 minutes, sometimes your air conditioning system can go through cycles too quickly—an issue known as “short cycling.” Short cycling is a term that means the air conditioner turns on and off in short bursts and does not heat or cool your house properly. An AC system that short cycles can become less efficient, resulting in increased energy bills and excess wear-and-tear, and can result in reduced comfort for your home. Troubleshooting the cause of short cycling should be performed quickly to prevent any further damage. If your air conditioning system is short cycling, here are four potential culprits. Causes of Air Conditioner Short Cycling. 1. Low Refrigerant Level: If the refrigerant is low in your air conditioner, your AC unit will not be able to properly cool your home. This inability to work properly will put stress on various components, causing them to work harder and in turn can cause your AC system to turn on and off irregularly. 2. Oversized Air Conditioner: If your air conditioner is too big for your house, it will cool the house very quickly and then shut off. This leads to higher energy bills, more maintenance calls than usual and can cause uneven cooling in the house. 3. Iced or Dirty Evaporator Coil: This is a common cause for people that have not had routine preventive AC maintenance performed on their air conditioner. The evaporator coil in your air conditioner removes hot air from your house, and when your AC unit can’t take out the hot air effectively, it has to work much harder to get the job done. This can lead to the air conditioner overheating and shutting off. 4. Dirty or Clogged Air Filter: If you don’t regularly replace the air filters in your house, the buildup can cause the air conditioner to work harder than necessary. When your air filter becomes too bogged down with dirt, dust and other microscopic particles, your air conditioner has to work harder to compensate for the lost airflow. This puts excess stress on the parts that operate the blower and compressor. These parts can overheat causing your air conditioning system to short cycle or even potentially break down resulting in costly repairs.
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mike_home
last year
Some thermostats have a cycle per hour setting. See if yours has this feature and the setting value. You can try setting it to 3 ot 4 cycles per hour to help reduce the cycle times..
HU-597194232 thanked mike_home
Elmer J Fudd
last year
last modified: last year
Older thermostats used to have a degree setting, as in - turn on the equipment when room temperature varies from the setting by .25, .5, .75, 1.0 degrees, etc.

Many newer thermostats have adjustable cycles per hour setting instead. I have some that are adjustable (lowest setting =2), and one at another location that is preset to 3 cycles. per hour. Remember that 3 cycles per hour can mean 10 minutes on, 10 minutes off, so that's not exactly longer cycling.

Shorter cycling is harder on the equipment, so many starts and stops. Heat exchanger doesn't fully heat up in heating mode, coil doesn't fully cool and remove moisture in cooling mode. I believe equipment is happier and lasts longer with longer run times. When I'm hanging around and find my temp setting is causing frequent ons and offs, I'll change the setting to a few degrees off the desired temp (Lower for cooling, a bit warmer for heating), let it reach that setting, and then return it to the preferred setting and let it coast back to that point.
sktn77a
last year
Post your Thermostat model. Sounds like an anticipation/CPH setting.
HU-597194232
Original Author
last year
Sure. Its a Honeywell t10 prosmart with
wdccruise
last year
last modified: last year
You can set the Honeywell T10 Pro maximum cooling cycles-per-hour in Installer Configuration, ISU #3140.
sktn77a
last year
Good luck trying to interpret that manual's explanation of anticipation ("droop")!!!
Elmer J Fudd
last year
Oh, those aren't so hard. When you enter the installer settings mode, you simply touch "Next" to scroll through the various settings until you get to the one you want.

On my Honeywells, it's necessary to enter a thermostat-specific passcode to get into the installation/settings area intended for pros. (This I suspect is to keep homeowners from messing with the settings and screwing them up). The passcode is a 4 digit number printed on the back of the thermostat, on the product ID sticker. Locked door now open.
wdccruise
last year
@sktn77a: "Good luck trying to interpret that manual's explanation of anticipation..."

I assume that's ISU 3090 'Backup Heat Differential' but one can just leave it at the default, "Comfort".

Short cycle ac concern

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klem1

Charles Ross Homes

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Short cycle ac concern

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