HVAC and New Construction, Home Additions and Multi-Family Dwellings

Pressing Matters: Choosing The Right Compressor Type For Your Split System Air Conditioning

Split system air conditioners offer a range of advantages over their ducted or window-mounted counterparts, providing excellent efficiency and cooling power without the need for expensive duct installation. However, since the compressor of a split system air conditioner is generally situated quite far away from the vent(s), choosing a powerful, high-quality compressor type is important. Without the right compressor a split system can become underpowered and will have its lifespan shortened as it is used at higher power levels to make up for the short fall.

Obviously, the size and power of your compressor are important factors to bear in mind, but you should also pay attention to the configuration of the compressing mechanism itself. Air conditioner compressors are available in a number of forms, each with its advantages and disadvantages when it comes to powering split A/C systems:

Reciprocating compressors

Also known as piston compressors, these simple and relatively inexpensive compressors function in a similar fashion to an automotive engine, using pistons to pressurise the refrigerant before sending it to the condenser. The great advantage of these systems is their rugged simplicity; piston systems have comparatively few moving parts and are generally robustly built to resist their considerable operating stresses. As such, they are ideal for low-maintenance, lower-cost split system installations, where constant use and a low chance of breakdowns are more important than sheer power.

Unfortunately, if a reciprocating compressor does suffer from mechanical failure, they can be difficult and expensive to repair, and you may be better off calling in professional repairmen or simply replacing the compressor. They can also be rather loud, especially when operating in high temperatures, and they may not be suitable for compressors attached to or placed against exterior walls due to excessive vibrations.

Centrifugal compressors

These versatile compressors function on the principles of centrifugal force and compress the refrigerant by sending it through a high-speed impeller. Centrifugal compressors are highly efficient and can provide powerful cooling for comparatively low energy costs. In addition, the simple impeller mechanism has few moving parts and creates very little friction when properly maintained, allowing a centrifugal compressor to work for long periods without repairs.

However, like reciprocating compressors, centrifugal compressors can be difficult to repair if and when they do malfunction. You should also pay close attention to the power capacity of any centrifugal compressor you consider buying; while they are generally very efficient, they tend to have strict power limits, and cooling particularly large indoor areas may require a more expensive, multiple-stage compressor. Make sure that a centrifugal compressor remains well-lubricated at all times to prevent wear.

Rotary compressors

These simple devices increase the pressure of your refrigerant by forcing it between two rotating screws or rotors. Alternatively, they may be fitted with spiral-shaped rotors known as 'scrolls'. Rotary compressors are simple devices with few moving parts and maintenance requirements, and they are generally inexpensive as a result. They are also quite quiet, especially if they use scroll rotors, making them ideally suited for smaller residential units and wall-mounted compressors.

The inexpensive simplicity of a rotary compressor comes at a price, however, and rotary compressors will generally have a significantly shorter lifespan than their more robust counterparts. They also lack efficiency compared to more expensive designs, and trying to use an underpowered rotary compressor to cool particularly large rooms can cause significant power usage and potential compressor damage.