Caught in the In‑Between: When You Keep Switching Between Heating & Cooling

You know the struggle.Early in the morning, it’s chilly outside, so you bundle up with a thick sweater. By lunchtime, the sun is scorching and you’ve gotta go down to a short sleeve shirt. Welcome to the Carolinas! During the spring and fall, Mother Nature likes to keep you on your toes. When you’re at home, you wanna keep things consistent and comfortable, but that often means switching back and forth between air conditioning and heating. What does this mean for your unit?

During this in-between, or “shoulder season,” there are a few problems we get calls for that are the result of switching back and forth from heating to cooling: Moisture in your ductwork, “Dirty Sock Syndrome,” and compressor damage. Not only that, but if you have a heat pump, your high-pressure safety sensor might go off.

The Primary Solution

Before we dive into the details of what could go wrong, let’s talk about the main thing you can do to prevent these problems. When the temperature outside keeps fluctuating from hot to cold, we recommend setting on your thermostat’s “Auto Changeover” feature (if it has one) and keeping the temperature range between 68-72 degrees. This allows your system to move between heating and cooling automatically, and it keeps the temperature in a range that prevents damage from either temperature extreme.

Moisture in Your Duct System

Your air conditioner’s first job is to dehumidify your home. Dehumidifying, in turn, causes your home to cool down. In fact, the AC was invented for the sole purpose of dehumidification. In 1890, Willis Carrier was commissioned to dehumidify a print shop because, during the warmer months, the ink would never dry. In the process, people learned that dehumidifying cools the air!

While your A/C cools your home, it draws out about 12 to 18 gallons of water from the air per day. This water is collected from the evaporator coil. When your heat comes on later in the evening, it’ll push hot air across your evaporator coil, which is wet from cooling your home earlier the same day. That hot air causes the water on the coil to evaporate, which gets humidity in your ductwork. This can make the area around your unit musty and humid, and it can even cause moisture to build up in your duct system!

Dirty Sock Syndrome

When you don’t stay on schedule with your filter changes, dust and debris can start to collect on your unit, specifically your evaporator coil. When this happens, the dust and debris mix with the moisture on your coils we talked about earlier, allowing bacteria and mildew to build up. When your heat turns on and blows hot air across the coils, not only does water then evaporate, but mildew also bakes off, releasing a dirty sock smell throughout your home. Unfortunately, this is a really common problem. The best way to prevent Dirty Sock Syndrome? Replace your filters regularly and remember to schedule your preventative maintenance.

Causing Damage to Your Compressor

Most thermostats have an automatic five-minute delay built into the electronics. Basically, when your AC shuts off, before switching over to heat, the compressor won’t restart for five minutes. It may seem annoying, but this is important! It allows your refrigerant to get back to its starting pressure. Start the unit too soon, and your compressor could lock up. This rest time helps protect your unit. If your system does not have an automatic delay, you should manually shut your unit down from your thermostat for five minutes before switching between heating and cooling.

Too Cold

During shoulder season, it can be tricky to find the right temperature to balance the hot days and cold nights. When you set your cooling point too low and the overnight temperatures drop, your evaporator coil is more likely to freeze over. This can stop your AC from working, and it can damage the system! To avoid this, it’s best to keep your temperature at or above 70 degrees.

Too Hot

If you have a heat pump and you leave your heat on during the warmer part of the day, it might trip your high-pressure safety sensor. Most of the time, this will auto-reset, but sometimes they don’t, so you’ll need to call out a professional to reset it. This is more of a problem for people who like to keep their home between 75 and 80 degrees all the time. If your home is that warm and the outside temperature is close to that same range, it can trigger the high-pressure sensor. Keep your temperature below 75 degrees to prevent this.

Just Right

If you have an automatic setting on your thermostat to switch between heating and cooling, you have the ability to set a temperature range instead of a set temperature. When you have this setting on, don’t set heating and cooling to the exact same temperature—take advantage of the ability to set a range (preferably between 68-72 degrees).

If you set your air conditioning to 72, your unit will begin to cool your home if it gets above 72 degrees. If you set your heat for 68 degrees, any time your home gets below 68, the heat will kick on. If you set both for the same temperature, or for too close of a degree, your heating and A/C will constantly be fighting each other to maintain an exact temperature and this can wear your unit out. Make sure you set your heating and cooling points at least a few degrees apart.

Making it Through Shoulder Season

Whether you prefer colder or warmer weather, the Carolinas still make it tricky to find the right balance in your home when the afternoons are hot and the nights are cold. The key is to set your thermostat between 68 and 72 degrees to protect your unit as it switches back and forth between heating and cooling while keeping you comfortable at home! Wanna make sure both your heating and air conditioning are prepared for any weather thrown your way? Schedule a Check’N’Check today!

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