What Is an Air Handler?

An air handler is the indoor cabinet that pushes heated or cooled air through your home's ductwork. Its main parts are a blower, a coil and a filter slot, and in some models an electric heating element as well. It works alongside an outdoor unit, either an air conditioner or a heat pump.

If you have a gas furnace, the furnace blower and cabinet do the job of an air handler, so you may not have a separate unit at all.

What is inside

The blower is a motor and fan wheel that draw air from your home through the return ducts and push it back out through the supply ducts. Next to it is the evaporator coil, which is connected to the outdoor unit by refrigerant lines. In cooling mode, warm indoor air passes over the cold coil, gives up its heat and moisture, and continues on as cool, drier air.

Many air handlers also hold a filter, a drain pan for the water the coil removes, and controls that coordinate everything with the thermostat. Electric models include heat strips that provide warmth when a heat pump alone cannot keep up.

How it fits into your system

Think of the outdoor unit as the part that moves heat outside or brings it in, and the air handler as the part that delivers the result to your rooms. With a heat pump, the same pair heats in winter and cools in summer. The air handler is the constant in both seasons, running whenever the thermostat calls for conditioned air, and sometimes running the fan alone for circulation.

Do you need one?

It depends on your equipment. A home with a gas furnace and central air conditioning normally uses the furnace as its air handler. A home with an all-electric system, a heat pump or a ductless setup with ducted indoor units will have a dedicated air handler, often in a closet, attic or basement.

If you are planning to switch from one type of system to another, the answer will change. A technician can tell you what your house has now and what it would need.

Looking after it

• Replace or clean the filter on schedule. For a 1 inch filter, that is typically every one to three months, and sooner during smoke season or heavy dust.
• Keep the area around the unit clear so air can reach it and technicians can work on it.
• Watch for water around the base, which can point to a clogged drain line.
• Listen for new noises, and notice weak airflow or rooms that stop getting air.
• Leave the electrical, refrigerant and blower repairs to a licensed technician.

A professional visit once or twice a year cleans the coil and blower, checks the drain and tests the controls. A dirty blower wheel can lose a surprising amount of airflow, which shows up as rooms that will not cool and equipment that runs longer than it should.

Location matters too. An air handler in a hot attic works harder in summer, and one in a cold garage can have its own issues in winter. Ask a technician whether insulation on the cabinet, the ducts and the drain line is in good shape, since small gaps in those details cause surprisingly large comfort problems.

When something sounds off

A blower that runs but pushes weak air, a unit that will not start, ice on the coil or lines, or a musty smell each point to a different fault. Turning the system off when you see ice or water is a safe first step, and then a call to a professional is the right next one.

Air-Tech works on air handlers of every brand for homes across the Tri-Cities and the surrounding towns. Call (509) 392-2021, and if the trouble starts after hours, ask for their 24-hour emergency service.