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Are you committing these 10 air conditioning sins?

Keep your cooling system running smoothly all summer long

four part collage including air condition filters, outdoor A/C units, and a temperature testing sensor. Credit: Reviewed / Séamus Bellamy / mphillips007 /slobo / KangeStudio / Getty Images

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If there’s one power we love to exert it’s over Mother Nature. When the temperature warms up, our fingers hover over the thermostat’s on button, waiting for the moment we can initiate a blast of cool air against one of her blazing hot summer days.

Up until recently, your air conditioning unit might have been out of sight and out of mind during winter. It’s tough to know whether those months of hibernation were beneficial for the tough job ahead when it cooling your home quickly and efficiently this summer.

We spoke to Joseph C. Wood, president of Boston Standard Plumbing, Heating and Cooling, for 10 commonly made mistakes people make with their A/C units. With his advice, you’ll have no problem keeping your cool this summer.

1. Not changing air filters frequently enough

A person shown holding a used air filter with dust.
Credit: mphillips007 / Getty Images

Don't believe your "90-day filter" is really good for 90 days, warns Wood. According to him, that's just how long it worked in a lab environment.

“Think of [all that] dust, dander, dog hair, and other things [in your home],” he says. “They’re not only bad for you, but also bad for your equipment and can lead to preventable problems.”

Mantra: A new filter is a happy filter.

2. Buying overly-rated filters

Illustration showing air flow through filter layers.
Credit: boonkue cherdpayak / Getty Images / Reviewed

You want the best, but is the “best” the best? Wood says to avoid buying filters making outrageous claims, even if they’re true. For instance, a one-inch wide filter that claims to catch 99% of all dust.

“Yes, capturing more from the air is a good idea in principle, but if your filter is too restrictive, you increase energy use and can lead to insufficient airflow,” he says.

If you don't have a 5-inch media filter, and instead have the skinny 1-inch type, buy something on the low to mid-range and change it monthly.

3. Not keeping extra air filters on-hand

A dirty filter shown next to a clean AC filter.
Credit: slobo / Getty Images

As seasonal shoppers flock to the store, it could be hard to find filters in stock. “Consider using auto-delivery apps to make sure you don't forget this critical item. Leaving a dirty filter is bad, but no filter is even worse,” he says.

4. Forgetting to remove a cover on your outdoor unit

Credit: galinast / Getty Images

If you leave a wooden board, condenser cover, or tarp wrapped on your outdoor unit, you could be in for big trouble.

“A compressor (the engine of your AC unit) changes the state of the refrigerant from vapor to liquid, over and over,” he explains. “It relies on air movement to do this, and if you restrict the air movement, you'll overheat and overwork the compressor.”

Do this for long enough, and you can fry the internal parts. Translation: you’re in for an expensive replacement.

Wood’s trick: Set a calendar reminder on the day you put it on (probably late fall) for the spring date to remove it.

5. Forgetting to do maintenance

A close up of a person wiping the evaporator coils on their air conditioner unit.
Credit: Reviewed / Jonathan Chan

You got through last summer without incident, but that doesn’t mean you’re in the clear this season. With 168 hours in a week, odds are your problem won't occur in the 40 9-to-5 ones.

Off-hour maintenance calls (and their hefty price tags) can be avoided through regular maintenance, which can spot little problems before they become big ones.

6. Running your A/C while too cold outside

A outdoor air conditioner unit shown outside in the cold snow.
Credit: galinast / Getty-Images

You might be excited to start up your A/C (after all, it’s a sign that it’s summer), but hold out until it actually gets hot. Running the system when it’s still a little chilly out can stress out the appliance and lead to premature failure.

“I would advise you not to run your A/C when it’s below 65°F outside, and most systems are designed around a 70°F to 75°F indoor temperature (with full summer temperatures outside),” he says. “Running it lower than that could cause refrigerant-side issues, which lead to compressor issues down the line.”

7. Starting and stopping your system frequently

A shown person adjusting the temperature on a thermostat.
Credit: Reviewed / Whitson Gordon

Rapid cycling is bad for the appliance and can shorten its lifespan, so consider letting your A/C system work as intended by "setting and forgetting it. The compressor is like a pump, and it prefers longer cycles,” says Wood.

8. Running your system when the landscapers are there

A close up of a person using a blower to gather leaves.
Credit: Bogdanhoda / Getty-Images

While the other aspects of your yard draw your attention (hello, patios and pools), your A/C unit also needs a little outdoor TLC.

“Your A/C unit needs to be in a clean environment, so have it turned off when landscapers come so it doesn't suck up dust and dirt,” says Wood.

Equally as important, keep the area clear for best performance and make sure it doesn't start sinking into the surrounding dirt or mulch.

9. Not keeping a service contract

Two A/C technicians standing in front of an out door A/C unit looking at a report.
Credit: fstop123 / Getty Images

Depending on where you live and how busy it gets, not keeping a service contract with a professional HVAC company could be the difference between getting service the same day and being placed at the end of the line.

According to Woods, most service contracts also include maintenance for a double win.

10. Letting the house get too hot

A temperature, humidity, and electrical usage sensor shown on a wood surface.
Credit: Reviewed / Séamus Bellamy

While it seems counterintuitive to turn the A/C on to save money, waiting until it gets unbearable might actually end up costing you more.

“The older days of turning appliances off when you go to work and then on when you get home are not the best usage,” explains Wood. “Considering half the neighborhood might be using the same logic, you could find yourself with burned out electronics on the hottest days.”

Consider leaving your home at 79°F on the really hot days while away and using a smart thermostat to turn it down a few hours before you arrive home.

A Wi-Fi-enabled thermostat can also learn your habits and preferences, making money-saving adjustments to the temperature without you having to worry. This way, “the appliance isn't struggling to make temps right in the peak of afternoon demand,” he says.

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