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The Role Metering Devices Play in AC Systems

Atlanta Heating & Air Solutions Mabelton
HVAC metering devices

When most people think of residential air conditioning systems, they envision the condenser unit and the evaporator coil. These are two of the most important parts of a typical home’s air conditioning system. The condenser coil contains the condenser coil and compressor, whereas the evaporator coil consists entirely of an indoor-installed coil. There are other parts in residential air conditioning systems, however, such as metering devices.

What Are Metering Devices?

Metering devices are components that are designed to reduce the pressure of refrigerant. Air conditioning systems use refrigerant as a heat transfer medium. Refrigerant will flow through your air conditioning system’s condenser coil and evaporator coil, during which it will transfer heat from your home’s indoors to the outdoors.

Refrigerant must be pressurized so that it can effectively absorb and release heat. Immediately before the evaporator coil is a pressure-regulating device. Known as a metering device, it will lower the pressure of the refrigerant so that it becomes cooler before entering the evaporator coil.

The Types of Metering Devices 

There are fixed metering devices, and there are modulating metering devices. They are both designed to reduce the pressure of refrigerant. The difference is that fixed metering devices have a static operation, whereas modulating metering devices have an adjustable operation. 

Fixed metering devices will always lower the pressure of the refrigerant by a specific amount. Modulating metering devices, in comparison, can adjust their pressure-regulating effects.

Fixed metering devices are more common in older air conditioning systems. If your air conditioning system is more than 10 or 20 years old, it may feature a fixed metering device. If you have a new air conditioning system, it probably features a modulating metering device.

Why Your AC System Needs a Metering Device

Your air conditioning system needs a metering device so that it can transfer heat from your home’s indoors to the outdoors. It will lower the pressure of the refrigerant immediately before the evaporator coil. As the pressure drops, the evaporator coil will become cooler. It will then be able to absorb more heat from the surrounding air at the evaporator coil.

Without a metering device, your air conditioning system will struggle to cool your home. The refrigerant will remain highly pressurized and hot as it enters the evaporator coil. As a result, the refrigerant will absorb less heat. If your air conditioning system has a faulty metering device, it will likely manifest in the form of poor cooling performance.


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