HVAC maintenance

A heating and cooling system works hard in the South. Long, humid summers mean the air conditioner or heat pump runs for months at a time, and a small problem like a clogged filter or a blocked drain line can turn into a breakdown on the hottest day of the year.

Most upkeep is simple. A few jobs you can do yourself in minutes. The rest belongs to a yearly visit from an HVAC technician. This guide covers both. If you're not sure what kind of system you have, start with what kind of HVAC system do I have?

What you can do yourself

Check the air filter every month

ENERGY STAR recommends checking the filter every month and cleaning or replacing it when it's dirty [1]. A dirty filter makes the system work harder and can damage the equipment. Keeping filters clean can lower an air conditioner's energy use by 5 to 15 percent, according to the Department of Energy [2].

Tips:

The filter is usually behind a return grille on a wall or ceiling, or in a slot at the indoor unit. Some homes have more than one.
Write the filter size down, or take a photo of the old one before you shop.
Pets, construction dust and a lot of pollen mean changing it more often.
If you want better filtration, the EPA suggests a filter rated at least MERV 13, or the highest rating your system can handle. Not every system can push air through a dense filter, so ask an HVAC technician which rating works for yours [3].
Mini-splits have washable filters in each indoor head. Clean them as the owner's manual directs.

A dirty filter is one of the most common HVAC findings. See air filter, vent and thermostat fixes for more.

Keep the outdoor unit clear

The outdoor unit pulls in air through its sides and pushes heat out the top. When leaves, grass clippings or plants crowd it, it can't breathe.

Turn off power to the unit at the breaker before you clean around it.
Clear leaves, branches and plants within about two feet of the unit [4]. Leave the top open.
Rinse the outside of the coil with a gentle spray from a garden hose. Don't use a pressure washer: it can crush the thin metal fins and permanently damage the unit [4].
Brush or vacuum the fins only in an up-and-down direction, in line with the fins [4]. If fins are bent, a fin comb can straighten them [2], or a technician can.

Keep an eye out for debris around the unit, plants growing too close and torn foam insulation on the copper refrigerant line. These are small fixes. See outdoor AC unit fixes.

Watch the condensate line

Air conditioners, heat pumps and high-efficiency furnaces make water as they run. A small pipe called the condensate line carries it outside or to a drain. When algae and sludge build up, the line clogs, and water backs up into the drain pan.

Signs of a clog include a musty smell, standing water near the indoor unit, water stains on a ceiling or floor, weak cooling, or a system that shuts itself off, often because a safety float switch turned the AC off when the pan filled [5].

Carrier suggests a simple preventive step between tune-ups: with the power off, pour a cup of distilled vinegar into the drain line's access point near the indoor unit [5]. If water is already leaking or pooling, or the line stays clogged, call a technician. See clogged condensate line.

Also check where the line ends outside. It should drain away from the foundation, not right next to it. A line that ends too close to the house is a quick fix. See condensate drain line repair.

Keep vents and returns open

Don't block supply registers or return grilles with furniture, rugs or curtains. Blocked returns starve the system of air. If one room is always too hot or too cold, it may be a duct problem: see ductwork repair.

Check the thermostat

If the system won't start, check the thermostat first: the setting, the batteries and whether it's reading the room correctly [2].

Test your carbon monoxide alarms

If you have a gas furnace, gas fireplace or any other fuel-burning appliance, the Consumer Product Safety Commission recommends carbon monoxide alarms on every level of the home and outside sleeping areas [6]. If a CO alarm sounds, get everyone outside and call 911 or the fire department. Don't go back in until responders say it's safe [6].

What a yearly tune-up covers

ENERGY STAR recommends a professional check of the cooling in spring and the heating in fall, before contractors get busy [1]. A typical tune-up includes [1]:

For any system:

Check thermostat settings and system controls, including safe startup and shutdown.
Tighten electrical connections and measure voltage and current on the motors. Loose connections can make the system unsafe.
Lubricate moving parts.
Check and clear the condensate drain. A plugged drain can cause water damage.

For cooling:

Clean the indoor (evaporator) and outdoor (condenser) coils. Dirty coils cut cooling ability.
Check the refrigerant level. Too much or too little makes the system less efficient.
Clean and adjust the blower for proper airflow. Airflow problems can reduce efficiency by up to 15 percent.

For gas heating:

Check gas connections, gas pressure, burner combustion and the heat exchanger. Faulty gas connections are a fire hazard, and a cracked heat exchanger causes unsafe burner operation.

The CPSC recommends having fuel-burning heating systems professionally inspected and serviced every year, including the flue and vent connections [6]. A HomeCloud evaluation may flag a furnace that needs servicing or a flue too close to wood or insulation. Those are jobs for a licensed HVAC technician.

Leave these to a licensed professional

Some HVAC work is not do-it-yourself work:

Anything involving refrigerant.
Electrical work inside the units or at the disconnect.
Gas lines, burners, flues and venting.
Opening sealed panels on the furnace or air handler.

If you smell gas, leave the home right away and call your gas company or 911 from outside. Don't flip switches or use anything that could make a spark.

A simple yearly schedule

When	What
Every month	Check the filter. Glance at the outdoor unit and the condensate line outlet.
Spring	Professional cooling tune-up. Clear the outdoor unit.
Summer	Watch for water near the indoor unit. Keep plants trimmed back.
Fall	Professional heating tune-up. Test CO alarms.

When repairs come up, see HVAC repair and service. If your system is getting old, compare the cost of replacing it and read about choosing a brand and installer.

HomeCloud is a licensed general contractor. We evaluate homes and price and do the repairs, including HVAC work.