What kind of HVAC system do I have?

Most homes in North Carolina, Georgia and Texas are heated and cooled by one of four kinds of systems: a gas furnace paired with an air conditioner, a heat pump, a packaged unit, or a ductless mini-split. They can look alike from the yard, but they work differently, wear out differently and cost different amounts to repair or replace.

Knowing which one you have helps you read a repair quote, plan for a replacement and ask better questions. This guide shows how to tell them apart and how to read the label on the equipment. When you're ready to price new equipment, see what an HVAC replacement costs.

Start outside: one box or two?

Walk around the house and find the outdoor equipment. Then find the indoor equipment, usually in the attic, a closet, the garage, the basement or the crawl space.

• Two pieces, an outdoor unit and an indoor unit, connected by copper lines: this is a split system. It is either an air conditioner with a furnace or air handler inside, or a heat pump. Split systems are the most common type of heat pump, with separate outdoor and indoor units [2].
• One large cabinet outside, with ducts running straight from it into the house: this is a packaged unit. Everything is in one enclosure instead of being split between indoors and outdoors [2]. These often sit on a pad beside the house.
• A small outdoor unit and one or more slim units mounted high on walls or in the ceiling, with no ducts: this is a ductless mini-split [1].

Gas furnace with AC, or heat pump?

This is the question most homeowners can't answer at first, because the outdoor unit of a heat pump looks almost the same as an air conditioner.

The difference is what the outdoor unit does in winter. An air conditioner only cools. A heat pump uses electricity to move heat instead of making it: in winter it pulls heat from the outdoor air into the home, and in summer it reverses and moves heat out [3]. So a heat pump's outdoor unit runs in both seasons.

Clues that you have a gas furnace:

• A gas line runs to the indoor unit.
• A vent pipe (the flue) runs from the indoor unit up through the roof or out a wall to carry exhaust outside.
• You get a gas bill in winter that rises with the cold.

Clues that you have a heat pump:

• The outdoor unit runs on cold days. It may pause now and then to defrost and drip water [1].
• The label on the outdoor unit says "heat pump."
• The indoor unit is an air handler with no gas line and no flue.
• Your thermostat may have a setting such as "aux heat" or "emergency heat," which turns on electric backup heat.

Some homes have both: a heat pump for most of the year and a gas furnace that takes over on the coldest days. If you see a gas furnace inside and the outdoor unit runs in winter, ask an HVAC technician to confirm how the system is set up.

Ductless mini-splits

A mini-split has an outdoor unit connected by refrigerant lines to one or more indoor "heads" that blow conditioned air straight into the room. There's no ductwork. ENERGY STAR describes them as a fit for homes or parts of homes without ducts, such as additions, converted garages and rooms over unheated spaces [1]. The mini-splits ENERGY STAR describes are heat pumps, so one system both heats and cools [1].

Each indoor head has its own filter that needs regular cleaning. See HVAC maintenance for what to look after.

How to read the label on the equipment

Every outdoor and indoor unit has a metal or paper data plate, usually on the side of the outdoor unit and inside the door or on the side of the indoor unit. Turn off the power before removing any panel, or just read the label that's already visible.

Look for these:

On the label	What it tells you
Brand and model number	Who made it and which product line. The model number often includes the cooling size.
Serial number	Usually includes the date it was made.
Refrigerant type	Which refrigerant the system uses. This matters when you replace only part of a system.
Electrical ratings	The circuit the unit needs. Useful for the technician, not usually for you.

Size. Air conditioners and heat pumps are sized in tons. One ton is 12,000 Btu per hour of cooling. Many model numbers include the size in thousands of Btu, so a "24" in the model number usually means 2 tons, "36" means 3 tons and "48" means 4 tons [4]. The pattern varies by brand, so treat it as a clue, not a rule.

Age. Manufacturers hide the manufacture date in the serial number, and the format changes from brand to brand and even decade to decade. On some units, the first digits are the week and the next digits are the year. Others use letters for the month or year, and some brands print the date right on the plate [4]. If you can't decode it, search the brand's website or ask a technician. Check the indoor and outdoor units separately. They aren't always the same age, especially if one part was replaced.

What the type and age mean for repairs and replacement

Age. ENERGY STAR suggests considering a replacement when a heat pump or air conditioner is more than 10 years old, or a furnace or boiler is more than 15 years old, especially if it needs frequent repairs or rooms are uneven [5]. Age alone doesn't mean a system has to go, but it changes the math on a big repair. A HomeCloud evaluation notes when a unit is beyond its useful life or nearing the end of it, so you can plan ahead.

Gas furnace with AC. The furnace and the air conditioner are separate machines, so one can fail while the other keeps working. Gas furnaces also have venting and gas connections that need a yearly professional check. The Consumer Product Safety Commission recommends having fuel-burning heating systems inspected and serviced every year [6]. If you smell gas, leave the home and call your gas company from outside.

Heat pump. One outdoor unit does both heating and cooling, so it works year-round and tends to see more running hours than an air conditioner. A problem with the outdoor unit can affect both seasons.

Packaged unit. Everything is outside in one cabinet, so there's no indoor unit to work around. Repairs and replacement happen in the yard, but the cabinet is exposed to weather year-round.

Mini-split. Each indoor head is part of the system, so the number of heads and the size of the outdoor unit both affect what a repair or replacement involves.

Split systems. The indoor and outdoor parts are designed to work as a matched pair. Replacing just the outdoor unit on an older system may not work if the refrigerant has changed, so the indoor and outdoor units are usually replaced together. See repair or replace for more.

For smaller problems, like a system that runs but doesn't cool, start with HVAC repair and service. For help choosing equipment, read the best HVAC brands.

HomeCloud is a licensed general contractor. When an evaluation finds a problem with your heating or cooling, the report explains it, and we can price the repair or replacement.

Sources

1. ENERGY STAR: Ductless heating and cooling
2. U.S. Department of Energy: Types of air-to-air heat pumps (fact sheet)
3. U.S. Department of Energy: Pump up your savings with heat pumps
4. Air conditioner age and capacity information (reference sheet hosted by Energy Trust of Oregon)
5. ENERGY STAR: When is it time to replace?
6. U.S. Consumer Product Safety Commission: Home heating equipment and carbon monoxide