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What is a Condenser?

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Central air conditioning systems have essentially two parts: an evaporator that removes unwanted heat from the air and transfers it to a refrigerant; and a condenser that removes unwanted heat from the refrigerant and transfers that heat outdoors.

Condensers are heat exchangers that induce condensation on the pressurized refrigerant, so that it changes phase from a gas to a liquid. The primary component of a condenser is the condenser coil, through which the refrigerant flows. The condenser is typically located outside of the building in central cooling systems.

Types of Condensers

There are essentially three types of condensers: air-cooled, water-cooled and evaporative. These types differ in how they remove excess heat:

  • Air-cooled condensers remove heat by blowing air over the condenser coil
  • Water-cooled condensers remove heat by pouring water over the condenser coil
  • Evaporative condensers do not typically use a refrigerant. They remove heat by allowing water to evaporate directly into the air

Air-cooled condensers are by far the most common type of condenser in residential systems.

Condenser Parts

Both split air conditioner and heat pump condensers are made of the same basic parts. The condenser cabinet contains the condenser coil, a compressor, a fan, and various controls. The condenser coil can be made of copper tubing with aluminum fins or all-aluminum tubing so heat can be rapidly transferred. The coil withstands a pressure of over 400 psi when the weather is very warm. It should be kept as clean as possible to maintain its heat transferring efficiency.

The condenser fan is a vital part and circulates the air across the coil to facilitate heat transfer. If the flow of air is blocked, the efficiency will be impacted or the compressor could fail. The area around the compressor's coil and fan must be free from dirt so that maximum airflow can take place. The compressor is the heart of the system since it compresses the refrigerant and pumps it to a coil in the form of a hot gas. In air conditioners this is cooled at the condenser into a warm liquid, and passes through a pipe into the evaporator coil where it expands and cools. In heat pumps, the hot gas is pumped directly to the evaporator coil to provide heat.

Major condenser manufacturers include Carrier, Heil, Fedders, Lennox, Rheem, Tempstar, and AireFlow.

Condensers In Air Conditioning

Condensers used only in air conditioning do not have many controls. A contactor is used to switch the power on and off. Capacitors start and run the motors. Some optional controls like brownout time delay, hard start kit, crankcase heater, and low ambience control are available. The compressor is protected by the brownout time delay, which shuts the contactor off when voltage drops and too much current is pulled in by the motors.

Heat Pump Condensers

These have controls that are more complex than those of the air conditioner. In addition to the contactor, capacitor, and other optional controls, there is also a reversing valve, defrost timer, and an adjustable temperature sensor. The flow of compressed gas is directed by the reversing valve to the condenser coil for air conditioning or to the evaporator coil for heating. The condenser coil extracts heat from air outside the home. When it does this, it becomes very cold and frost collects on it. An excess of frost restricts the flow of air, reducing the coil's effectiveness. The defrost control automatically switches to the air conditioning mode even without the condenser fan running. This makes the ice melt when the hot gas runs through the coil, after which the system switches back to heating mode.

If you want more information about how your air conditioner works, you may wish to read about the compressor, which pressurizes the refrigerant.

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