Central air conditioning systems and mini-split systems both use a split design. This approach utilizes two separate units — an indoor evaporator/air handler and an outdoor condenser. Mini-split systems add a few more elements to the indoor unit since they eschew ductwork in favor of a single blower, but the concept is still the same.
Two separate units might seem like a costly, complicated, and inefficient design, but it's critical to the effective operation of your air conditioning system. Not only do these two units help keep your home cool, but they help do so in a way that minimizes your utility bills and improves efficiency.
What Do Air Conditioners and Transportation Have in Common?
You might not think of your air conditioner as a transport system, but it's a surprisingly apt description. Your air conditioner doesn't create cool air. Instead, it moves heat (or energy) away from your home. Energy transfer and transport processes are complex, but you don't need to be a physicist to learn enough to understand your air conditioning system.
Your air conditioner uses a concept known as the refrigerant cycle to transport heat. During this cycle, the refrigerant travels between the outdoor condenser coils and indoor evaporator coils. The critical part of this process is that the refrigerant doesn't remain in a single state. Instead, it travels through the system at times as hot gas or vapor and at other times as a cool liquid.
Cold liquid refrigerant moves through your evaporator coils in a typical AC system, absorbing heat from the surrounding air. The heated refrigerant becomes a warm gas as it leaves the evaporator and continues its journey outside. Once it reaches the condenser unit, the compressor squeezes it into hot vapor. Finally, it releases its heat as it travels through the condenser coils, becoming a liquid once again.
How Does the Split System Design Help?
There are two critical moments for the refrigerant cycle: absorbing heat and then releasing it. Since removing heat back into your home would be counterproductive, the split design allows your air conditioner to reject heat back into the outdoor environment. As a result, your condenser unit needs sufficient airflow to allow the hot refrigerant to cool and condense.
Likewise, your evaporator unit needs a steady supply of (relatively) warm air. If the air near the evaporator cools too quickly, the coils may freeze. Ice on your evaporator coils can insulate them, preventing the refrigerant from absorbing energy and ultimately impacting the efficiency of the refrigerant cycle.
Ultimately, your air conditioner relies on both halves of its system to operate effectively and efficiently. If problems develop with either unit or the refrigerant plumbing between them, it's best to contact an HVAC professional as soon as possible to restore your system.