Why Does My Furnace Turn On in the Summer?

You’ve scheduled a routine cooling tune-up to prepare for the rising temperatures and intense humidity, courtesy of Louisville summers. As you prepare to binge your favorite show, you suddenly notice warm air wafting from the closest vent. “Why does my furnace turn on in the summer?” you wonder.

A1 Mechanical specializes in residential and commercial furnace repair in Louisville, KY. We can think of a few reasons for this phenomenon that we’ll share below. Let’s troubleshoot this case of unseasonal heating. 

What Type of Furnace Do You Use?

Sometimes, a furnace operating during summer is a feature, not a bug. Other times, it’s an HVAC system malfunction that requires you to shut down the heating system and contact a technician before using it again.

You need to know what type of heating system you use before answering the question at hand. Which of the following system models does your building have?

• Central HVAC system: Do you have vent registers in every room, an indoor unit hidden in a storage area, and an outdoor unit on the side of your building? That means you probably have a central HVAC. 
• Non-central HVAC system: Wall- or window-mounted units that use pipes instead of visible ductwork typically indicate a non-central system. 
• Boiler: These systems have their own plumbing networks connected to radiators along walls or baseboards. 

“Why does my furnace turn on in the summer?” Once you know which system you use, you’re halfway to an answer. 

Troubleshooting the Issue

If you schedule routine boiler, heating, or furnace maintenance during autumn, you shouldn’t have anything out of the ordinary pop up for the rest of the year, especially after switching to cooling mode. However, strange, new symptoms can occur, and a little knowledge goes a long way. Below, we’ll examine why some heating systems might operate during warm weather and whether you should be concerned. 

If You Use a Central HVAC System…

Then your HVAC system depends on the same blower fan to operate year-round. You might switch from heating to cooling on your thermostat, but the same fan will push air through the vents. If you’ve mistakenly set the thermostat to fan mode operation, the system will constantly run the fan without circulating warmth or heat unless indoor temperature changes trigger it.

As a result, you might feel some residual heat circulation or normal, room-temperature air coming from your vents. Check to ensure the system still works properly by knocking your cooling settings down a couple of degrees to initiate the air conditioner. If the vents produce crisp, cool air, you’re in the clear. 

If You Use a Different HVAC Setup…

A brief rundown of commonly used non-central HVAC systems includes:

• Heat pumps
• Ductless mini-splits
• Window units
• Evaporative coolers

These models provide both heating and cooling, but residents of Louisville, Kentucky, often have backup furnaces in case the winter temperatures plummet below freezing. If you use one of these in conjunction with a furnace, you can probably cut all furnace utilities throughout the warm season. 

“But why does my furnace turn on in the summer?” you ask. Double-check your thermostat settings to make sure you initiated the cooling function. Ask a technician to check for zoning control issues or signal problems during your autumn maintenance visit. They should be able to resolve any problems before you switch to your furnace for the winter. 

What About Boilers?

While boilers are not furnaces, they are a type of heating system that may use resources when not in use. Some boilers work in conjunction with water heaters, while others stand alone. If connected, your boiler might power up in tandem with the heater.

That means it shouldn’t heat your home or business at all when you switch to air conditioning settings. You might just hear the water heater elements heating their separate tanks.  

However, a boiler that is separate from the water can use resources to heat its water supply without heating the building. Revisit your owner’s manual to find out how to turn the boiler off without powering down the water heater. 

Should You Turn Your Furnace On During the Summer?

“Why does my furnace turn on in the summer?” You know the answers and what to do in response to this concern. However, you might wonder whether you should run your furnace from time to time or just leave it off all summer.

That’s entirely up to you, though it’s unnecessary with regular heating and cooling tune-ups. Professional technicians follow a detailed maintenance checklist for every visit. Plus, you can prepare your furnace or other heating system for its summer slumber by:

• Cutting the power and/or fuel supply to your central heating mechanism or separate boiler. Your user manual should provide details on how to do this. Otherwise, ask your HVAC technician how to do it safely during a maintenance booking. 
• Double-checking your thermostat and familiarizing yourself with the settings. Some property owners confuse the settings. The average device allows you to choose automatic or fan settings, enabling the fan to run only when the temperature changes or indefinitely. 
• Returning power to and test-running your heating system in early autumn. Moisture may find its way into the heating mechanisms throughout the summer. Run the system and inventory any strange occurrences. You can relay them to your technician during your tune-up. 
• Booking a tune-up with A1 Mechanical in Louisville, Kentucky. Regardless of whether your furnace has issues upon startup, you should always schedule a maintenance visit to ensure everything works smoothly. 
• Performing quarterly maintenance throughout the year. Filter replacements, vent cleanings, and other small tasks keep the system clean. 

Let A1 Mechanical Have a Look at Your Furnace in Louisville, Kentucky

“Why does my furnace turn on in the summer? I’ll just ask A1 Mechanical for help. Their technicians know what to do.”

That’s us! Call 502-708-2247 to maintain, repair, or replace your furnace in Louisville, Kentucky. We’ll send a skilled technician to address any HVAC problem or concern.