Getting Your Air Conditioner Ready for the Heat

In Calgary, the shift from heating to cooling can feel abrupt. One week the furnace still kicks on overnight, and the next a wave of heat rolls in and people start wishing for a cool breeze. We spend so much of the year focused on staying warm that the cooling side often gets ignored until everyone is sweating. Setting aside an hour or two on a mild spring weekend to go over your central air conditioner can help you avoid a last minute repair call when every technician in the city is already busy.

Clear the Outside Unit

Your air conditioner has two main parts: an indoor coil that sits on your furnace and an outdoor unit called a condenser. The condenser is the big metal box in your yard with a fan inside. Its job is to release the heat that has been removed from your house. For that to work properly, it has to be clean and have enough space for air to move around it.

Over the fall and winter, leaves, twigs, and dirt can collect around the base and against the sides. The first step is to clear all this debris away. Take a look at nearby plants. If shrubs have grown over the winter and spring, trim them back so they are not blocking the airflow. In many Calgary neighbourhoods, especially down in the Bow River valley, poplar trees will soon be releasing their cottony seeds. This fluff can completely blanket a condenser's coils in a matter of days and choke the system.

I remember a house in the southwest where the homeowner was worried about his high electricity bills and poor cooling performance. When I went outside, the condenser unit looked like it was wearing a fuzzy white sweater. It was completely covered in poplar fluff. We shut off the power at the breaker and I showed him how to clean it. We used a garden hose with a gentle spray to wash the fluff and dirt away from the delicate aluminum fins.

When you clean the fins, spray the water from the inside out, if you can get access, to push the dirt away instead of driving it deeper. Use a gentle nozzle setting. A high pressure spray can bend the soft metal fins. If you find some are already bent, maybe from hail or a stray soccer ball, you can buy a small tool called a fin comb to gently straighten them. Finally, check that the concrete pad under the unit is still level. If the ground has shifted and the unit is tilting, it can affect its operation over time.

Change the Furnace Filter

The single most important maintenance task for your whole heating and cooling system is also the simplest: changing the filter. Your air conditioner uses the same fan and ductwork as your furnace. When your A/C is running, air from your house is pulled into the return ducts, through the filter, over the cold indoor coil, and then pushed back into your home through the supply registers. If the filter is clogged with dust and dirt, it restricts this airflow.

Poor airflow makes every part of the system work harder. It can lead to reduced cooling, higher energy bills, and extra strain on the fan motor. In some cases, a very dirty filter can restrict airflow so much that the indoor coil gets too cold and freezes into a block of ice, which stops the cooling process entirely. Changing the filter is a straightforward homeowner job. You will find it in a metal slot on the furnace, right where the main return air duct connects. Slide the old one out, note the size printed on its cardboard frame, and slide a new one in, making sure the arrows for airflow are pointing toward the furnace.

Check the Condensate Drain

Part of an air conditioner's job is to dehumidify the air. As warm, moist indoor air passes over the cold coil, water condenses on it, like on a cold glass of water on a hot day. This water drips into a collection pan and drains away through a small plastic pipe, usually to a floor drain near the furnace. This is the condensate line.

Because it is a dark, damp environment, this line can sometimes become a breeding ground for algae and gunk, which can form a blockage. If the line clogs, the collection pan will overflow, spilling water onto the floor or, in some setups, into the furnace itself. This can cause significant water damage. Before the cooling season starts, it is a good idea to make sure this line is clear. You can often disconnect the pipe near the furnace coil and carefully pour a small amount of water or a water and vinegar mixture through it to see that it drains freely into the floor drain. If it backs up, you may need to clear the blockage with a wet-dry vacuum or by blowing it out. If that does not go well or the line is buried inside a finished wall, that is a good time to call in a technician.

Do a Test Run

Once you have cleaned the outdoor unit, changed the filter, and checked the drain line, it is time for a test. Pick a reasonably mild day. There is no point running the A/C when it is cold outside. Set your thermostat to the "Cool" setting and lower the temperature a few degrees below the current room temperature. The system should start up within a few minutes. You will hear the furnace fan turn on, and then the outdoor condenser should come on with a hum and the whir of its fan.

Let it run for ten or fifteen minutes. Go outside and listen to the condenser. It should run steadily without loud clanking, rattling, or grinding sounds. Go back inside and hold your hand up to a supply register. The air coming out should feel noticeably cooler than the air in the room. Seasonal maintenance is a good habit for all your home's mechanical systems, not just the cooling. In winter, for example, you want to keep your garage door moving without trouble. If anything seems wrong during your test run, like strange noises or no cool air, shut the system off at the thermostat and contact a qualified HVAC technician. It is better to find a problem now than on the first scorching hot day of summer.