How to Help Your Air Conditioner Survive a Heat Wave
When temperatures climb into the mid-90s or even exceed 100°F, your home's air conditioning system is under tremendous stress. Every HVAC contractor sees an increase in breakdowns during these stretches of extreme weather, and many of those service calls could have been prevented with a little preparation.
The good news is that there are several simple things homeowners can do to help their air conditioning system perform at its best while reducing unnecessary wear and tear.
Start With the Air Filter
If you only do one thing before a heat wave, check your air filter.
A dirty filter restricts airflow, forcing the blower motor and air conditioner to work harder than necessary. Reduced airflow can also allow the evaporator coil to become excessively cold, reducing cooling performance and, in some cases, causing the coil to freeze.
For most residential HVAC systems using a standard one-inch filter, I generally recommend a MERV 8 filter unless your HVAC contractor or equipment manufacturer specifies otherwise.
One mistake I see fairly often is homeowners installing highly restrictive "allergy" filters purchased from a home improvement store without realizing the increased resistance they create. While those filters are well-intentioned, many residential HVAC systems simply aren't designed to move enough air through them.
Always follow your equipment manufacturer's recommendations, but avoid assuming that the most expensive filter is automatically the best choice.
Give the Outdoor Unit Room to Breathe
Your outdoor condenser rejects heat into the outside air. If the coil is covered with cottonwood, grass clippings, dirt, or leaves, it can't do that job efficiently.
Take a few minutes to:
Remove leaves and debris from around the unit.
Trim shrubs and vegetation back at least two feet.
Gently rinse the condenser coil with a garden hose if it's visibly dirty. Avoid using a pressure washer, which can damage the delicate aluminum fins.
A clean condenser coil allows the system to reject heat more efficiently and reduces stress on the compressor.
Understand What Your Air Conditioner Is Designed to Do
One of the biggest misconceptions I encounter every summer is that an air conditioner should be able to maintain any indoor temperature regardless of the weather outside.
That's simply not how residential HVAC systems are designed.
Most properly operating residential systems are designed around an indoor-to-outdoor temperature difference of approximately 20°F under design conditions. When outdoor temperatures reach 100°F, expecting the home to maintain 70°F throughout the hottest part of the afternoon may simply be unrealistic.
That doesn't necessarily mean the system is broken.
If it's an exceptionally hot day, consider raising the thermostat a degree or two during the afternoon. The system will often recover more easily once outdoor temperatures begin to fall in the evening.
Don't Keep Turning the Thermostat Down
If the house reaches 78°F, setting the thermostat to 65°F won't make the air conditioner cool any faster.
Residential air conditioners operate at essentially the same cooling capacity whenever they're running. Lowering the thermostat dramatically only tells the system to run longer.
Choose a reasonable temperature and let the system do its job.
Keep Supply and Return Registers Open
Closing registers in unused rooms is a common attempt to save energy, but in most homes it actually works against the HVAC system.
Your ductwork was designed to move a certain amount of air. Closing multiple registers increases static pressure inside the duct system and can reduce overall airflow through the equipment.
Likewise, avoid blocking return grilles with furniture, storage boxes, or curtains. Your HVAC system can only cool the air it is able to circulate.
Reduce Heat Inside the Home
Every degree of heat you keep out of the house is one less degree your air conditioner has to remove.
During extreme heat:
Close blinds or curtains on sun-facing windows.
Delay using the oven until evening if possible.
Run bathroom and kitchen exhaust fans only as long as necessary.
Limit unnecessary heat-producing appliances during the hottest part of the day.
Small changes throughout the house can noticeably reduce the cooling load.
Don't Ignore Unusual Symptoms
If you notice weak airflow, warm air coming from the vents, unusual noises, water around the indoor unit, or the system repeatedly cycling on and off, don't assume it will fix itself.
Addressing a minor issue early is often far less expensive than waiting until the system fails completely during the hottest weekend of the year.
Don't Forget About Your Duct System
The air conditioner can only cool the air that your duct system is able to deliver throughout the home.
If the ductwork is heavily contaminated, has damaged sections, disconnected ducts, or significant air leaks, your HVAC system may have to work harder to keep the home comfortable.
Professional duct cleaning isn't something that needs to be performed every year, but if your ductwork hasn't been cleaned in many years—or if you've recently completed renovations, have pets, or moved into a previously owned home—it can be an important part of maintaining a clean, efficient HVAC system.
The Bottom Line
Heat waves are hard on air conditioning equipment, but they're hard on homeowners too. A few simple maintenance steps—changing the filter, keeping the outdoor unit clean, maintaining good airflow, and understanding the limitations of the system during extreme weather—can go a long way toward improving comfort while reducing unnecessary stress on your HVAC equipment.
At Duct Doctor USA of Southern New Jersey, we believe an informed homeowner makes better decisions. Whether it's professional duct cleaning, dryer vent cleaning, or simply understanding how your HVAC system operates, our goal is to help you get the most from your home's heating and cooling system for years to come.
About the Author
Anthony J. Micale III is the owner and operator of Duct Doctor USA of Southern New Jersey and holds Air Systems Cleaning Specialist (ASCS) and Ventilation System Mold Remediator (VSMR) certifications through the National Air Duct Cleaners Association (NADCA). He has cleaned thousands of residential and commercial HVAC systems throughout South Jersey and specializes in HVAC system cleaning, airflow optimization, duct repairs, dryer vent cleaning, and indoor air quality.