Unfortunately, without knowing more about your house, your air conditioner, and the outside temperature, we can’t tell you why it takes so long for your air conditioner to cool down. But here’s what we can tell you: something is wrong if your air conditioner keeps running all day without cooling your home to the desired temperature.
If your air conditioner is taking a long time to cool your house, one of the following six issues is most likely to blame:
- It’s very hot outside
- A dirty air filter
- Refrigerant leaks
- Your outside unit is too dirty
- Leaky ducts
Reason #1: It’s very hot outside
The hotter it is outside, the more work your air conditioner must do to keep your home at a set temperature. Your air conditioner was built to maintain design temperatures, which are the various outdoor temperatures that your city stays between 99 percent of the year.
Reason #2: A dirty air filter
Because a filthy filter restricts the amount of air pulled back into your system to be cooled, it essentially “suffocates” your air conditioner. As a result, a dirty filter “asphyxiates” your air conditioner. Change your dirty air filter as soon as possible.
Reason #3: Low refrigerant
Refrigerant is an essential component of your air conditioner. It’s the cooling liquid/gas that absorbs heat from the air inside your home and sends it outside. If your AC lacks refrigerant, it will not be able to cool the air in your home.
If you have a leaky line, it’s virtually always due to a refrigerant loss, which implies there is a hole somewhere in the lines that move the gas.
Only a specialist can and should repair a refrigerant leak. Your technician should first address the problem, then refill your system with new refrigerant. Any refrigerant leaks should be fixed by a professional called a cooling expert.
Reason #4: Your outside unit is too dirty
A filthy outside condenser unit. The outside condenser is the component of your AC system that distributes heat from your refrigerant to the ambient air.
If your outside unit is visibly filthy or if the condenser coils are badly soiled, your AC will have a hard time distributing heat, which means it will take longer to cool your home. Solution: Consider cleaning your outside unit. If you have unclean condenser coils, contact an air conditioning specialist to get them cleaned for you.
Reason #5: Leaky ducts
Leaky ducts make it more difficult for your air conditioner to cool your property. Ductwork leaks can occur in two forms:
- A supply duct leak: If your supply ductwork has holes or faulty connections, you’ll lose conditioned air to leaks and take longer for your home to feel cool. A return duct leak is shown here.
- A return duct leak: If your return ductwork leaks, your AC system isn’t able to draw enough air from your house to cool it, which is why it takes longer for your home to feel comfortable. Consider a leaky straw: if there are holes in the straw, you may not drink as much as you would if there were no holes.
Have an HVAC professional check your ductwork for leaks and holes and repair them. According to the Energy Star program, typical homes lose 20–30% of the air that passes through the ductwork due to leaky ducts.
Reason #6: Your AC is too small or too old
- Your air conditioner is too small: Your air conditioner will run continuously but not cool your home if it is too little.
- You have an old air conditioner: As older air conditioners become less efficient, they will take longer to cool your house.
Contact a professional to inspect your air conditioner. A technician can do a Manual J Load Calculation to find out what size your air conditioner should be for your house. The expert will also inform you if your present AC unit is too outdated and discuss alternatives with you for upgrading it.