What are the 2 pipes in air conditioner?

Author: Oleta Haag  |  Last update: Monday, January 12, 2026

Connecting the condenser unit to the evaporator coils are two pipes through which refrigerant travels back and forth.

What are the two pipes coming out of my AC unit?

The big one (cold) is the suction line. The small one is the liquid line (hot; no need for insulation). Both of these lines run all the way back to your coil.

What are the 2 lines coming out of an AC unit?

Refrigerant lines are two copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil. The larger line typically carries a cool gas and is insulated. This is commonly referred to as the suction line, but it is also called the return line or vapor line.

What are two pipes in AC?

For example, a two-pipe system includes only one supply line and only one return line to the unit. Fan coil units and unit ventilators served by a two-pipe system contain only one coil which serves as the heating and cooling coil, depending upon the system.

What are the 2 lines on an air conditioner?

One is called the suction line. This is the inlet pipe to the compressor routing from the evaporator coil indoors to the outdoor condensing unit. The second line is called the Liquid Line (discharge line) leading from the outlet of the compressor.

Titus Timeout Podcast - 2-Pipe vs 4-Pipe Systems

Why does my AC have two hoses?

Dual-vent portable-AC units have two hoses: one to function as an exhaust tube, and the other to work as an intake. The second hose combats negative air-pressure by drawing in air from the outside to supplement the air that is lost when exhausting.

What is the two line on AC?

The suction line connects the evaporator to the compressor, the discharge line connects the compressor to the condenser, and the liquid line connects the condenser to the expansion device.

What are the pipes connected to an air conditioner?

In the air conditioning piping for building facilities, two main types of pipes are primarily used: carbon steel pipes for piping (SGP) and copper pipes for general refrigerant piping. For drain and wastewater applications, vinyl chloride pipes are used.

What are the two refrigerant lines?

The large line carries cool gas refrigerant and is called the suction line, return line, or vapor line. The thinner line carries hot liquid and is called the liquid line or discharge line. If you have a basement, you can see the two lines come in through the exterior wall.

What is 2 pipe HVAC?

A 2-pipe HVAC system is one that uses the same piping alternately for hot water heating and chilled water cooling, as opposed to a 4-pipe system that uses separate lines for hot and chilled water. Two-pipe originated 50 or 60 years ago as a cost-effective way to add air conditioning.

What are the 2 AC drain lines?

Typically every air conditioning system has 2 condensate drain lines. The primary line drips continually when the a/c is running. When the primary line becomes clogged (usually with algae or sludge), the secondary or emergency line will provide relief.

Why does my air conditioner have two drains?

Models With Two Drain Plugs

The upper drain plug is provided to allow automatic draining when the appliance is set for Dehumidify Mode or Dry Mode in high humidity areas. The lower drain plug is typically used for Cooling or Heating Mode, or for draining the tank for storage.

How do I know if my AC lines are clogged?

A clogged AC drain line symptoms include:
  1. Musty, moldy smell near your indoor unit or in air from the registers/vents.
  2. Standing water near the indoor unit.
  3. Water damage in areas near the indoor unit.
  4. AC system is not cooling your home.
  5. AC system shuts down or doesn't turn on.

What does a two-pipe system look like?

The 2 pipe system consists of a single water coil connected to two pipes (supply and return) and one valvle that can serve as either chill water coil or hot water coil depending on the mode of the system.

What is the pipe coming out of the air conditioner?

The emergency drain line is called that for a reason! The pipe down low is the primary or main condensate line from your air conditioner. Seeing water dripping or trickling from this line is normal operation, and you can probably relax – but read the rest of this article before you do.

Where to drain a condensate line?

Condensate lines should terminate in a location that allows for safe and effective drainage. This can include outdoor areas, a nearby floor drain, or a dedicated drain connected indirectly to your plumbing system to prevent contamination.

What are the 2 pipes on AC unit?

If you're asking about the two copper lines coming out, that's your lineset that Carrie's the refrigerant from the outdoor unit to the furnace or air handler coil then back to the unit.

Why do some air conditioners have two hoses?

Since the process of cooling air generates heat inside the unit, the second hose intakes air from the outside which is used to cool the unit's condenser coils and compressor. Dual hose units can cool an area more quickly and efficiently than the single hose variants, making them ideal for larger spaces.

Where does Freon leak from an AC unit?

In our experience, if there is a Freon leak in your air conditioner, 9 times out of 10, the leak will be located in the copper tubing of your evaporator coil. The location is nearly always in plate-fin copper tubing, which is made paper thin for maximum thermal efficiency.

What are the two AC lines called?

Line sets consist of two semi-flexible copper pipes to connect the outdoor air conditioner or heat pump to the indoor air handler. The smaller pipe is called the liquid line. The larger pipe is referred to as the suction line.

What is the pipe that leads to a condenser from the compressor?

The function of the discharge line is to transport the superheated high-pressure steam from the compressor discharge valve to the condenser inlet.

What is the PVC pipe coming out of my AC unit?

Condensate lines are typically crafted with PVC pipe or metal, and they provide a funnel for the humidity and condensation created by air conditioner evaporator coils as the systems run.

What happens if the evaporator fan goes out?

If the evaporator fan motor is broken, then cool air won't circulate properly. Sometimes you wind up with a freezer that's still pretty cold—because that's near where the coils are—but a fresh food compartment that isn't cold at all because the cool air isn't getting pushed there.

What are the two parts of an AC unit called?

Any central HVAC system contains two major parts. The outdoor unit, called a condenser and an indoor unit called a furnace. Though the furnace is most associated with heat, it plays a major role in the cooling process as well.

What are the two breakers on AC unit?

One breaker is connected to the air handler, the other to the condenser. Different issues will cause one or the other breaker to trip; however, it is seldom the case both breakers will trip simultaneously. Power outages, lightening, a faulty transformer, or brown-outs could possibly cause both breakers to trip at once.

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