AC Condenser, What is an AC Condenser, How does an AC Condenser work

AC Condenser speaks to what is an AC Condenser, how does an AC Condenser work and explain AC Condenser.

The condenser unit direct expansion cooling occurs when heat is removed from the air stream by the evaporator cooling coil. The cooling coil outlet suction line sensor which senses the refrigerant discharge temperature, modulates the control valve on the inlet of the coil.This may be considered the heart of the system.

This regulates the flow of refrigerant through the coil to maintain the desired discharge air temperature.

On small systems this control valve is controlled open or closed. On refrigerant coils, care must be taken in the setting of the refrigerant discharge air temperature, so that the refrigerant discharge air temperature is limited to a low of 57 F.

If this is not so it is possible that moisture that condenses on the coil surface may freeze and eventually the direct expansion cooling coil will become blocked with ice or at least frosted over. This can also happen if there is low air flow across the evaporator coil.

Control theory is that a controller sensing zone temperature energizes an electric solenoid valve and a thermostatically self operating expansion valve. These are located in the inlet to the piping for the ac condenser unit direct expansion cooling coil.

The solenoid is opened on a demand for cooling and the thermostatic expansion valve (TXV) regulates the amount of refrigerant that passes through the coil. The vaporized refrigerant in the tubes of the direct expansion cooling coil absorbs heat, which is transferred from the air passing over the coil tubes.

The thermostatic expansion valve is located in the refrigerant line to the cooling coil. The compressor operates while the thermostatic valve allows refrigerant into the cooling coil. When the desired coil temperature is reached, the TXV throttles the flow of refrigerant to assure that only gaseous refrigerant leaves the cooling coil outlet and moves on to the suction side of the compressor.

AC Condenser Control

When the refrigerant demand is satisfied the solenoid valve closes. As the compressor keeps reducing the pressure on the suction line, a constant pressure is reached which turns off power to the motor automatically.

On large ac unit systems it is necessary to control the compressor discharge in stages to match the loads and prevent cycling of the compressor motor.

The sensor for control of the unloading of the cylinders can be based on suction pressure of the unit, temperature of the return air or temperature of the occupied space.

Packaged AC Condenser Unit

The ac condenser unit provides refrigerant flow to the remote evaporator direct expansion coil located in the air system. It is usually meant to be operated during summer months only, but when called for, winter operating packages are available.

Sequence of Operation for air conditioning condenser unit:

The unit operates automatically when:

  • compressor starter switch is in the ON position.

  • condenser air conditioner switch is in the ON position.

  • outdoor air temperature is above 55 F.

  • air system is ON.

  • cooling coil discharge air temperature is above set point.

    On a demand for cooling this sequence occurs: <

  • control relay energizes the solenoid valve at the DX coil.

  • evaporation of refrigerant in the coil starts to raise the pressure on the suction side of the machine which energizes the control relay at the condensing unit control panel.

  • control relay for the compressor and related control circuits is energized.

  • control relay for the condensing unit fan control circuit is energized.

    The thermostatic expansion valve (TXV) is located in the refrigerant line to the cooling coil. The compressor operates while the thermostatic expansion valve allows refrigerant into the cooling coil.

    When the desired coil temperature is reached the TXV throttles the flow of refrigerant to assure that only gaseous refrigerant leaves the cooling coil outlet and moves on to the suction side of the compressor.

    When the refrigerant demand is satisfied, the solenoid valve closes and as the compressor keeps reducing the pressure on the suction line a constant pressure is reached which turns off the power to the motors automatically.

    Building Cooling Systems

    Return from AC Condenser to homepage

    Hard copy and E book for sale. Introduction to Building Mechanical Systems. Click here.

    Hard copy and E book for sale. What's Killing You and What You Can Do About It. A humourous look at ageing and disease. Click here.