GREE Multi Ductless Mini-Split Outdoor 36 BTU, 4 Zone

The function of air conditioning systems involves trapping heat energy within a space and conveying it outside. The process involves a closed loop of coolant flowing between an evaporator coil in the interior air handler that takes in heat from the indoor air and an exterior condenser where a compressor releases heat from the coolant into the outdoor air.

A conventional central air conditioning system relies on ductwork to move the cooled air throughout the building. In contrast, a ductless mini-split air conditioning system avoids the need for ducts by situating the air handler unit within the room, either recessed in the ceiling or mounted on a wall. The fan within the air handler unit blows air directly into the room by circulating air across the coils.

The air handler in a ductless mini-split air conditioning system is connected to its condenser through a line set, which consists of a pair of semiflexible copper tubes that circulate refrigerant between the two components. To install the system, the line set, power cord, and condensate drain must pass through an exterior wall, typically through a three-inch hole. This setup offers an attractive solution for those who desire air conditioning but lack ductwork or space for duct installation.

Many mini-split systems have the ability to function as heat pumps, in addition to their air conditioning capabilities. Heat pumps work by reversing the flow of coolant, causing it to evaporate in the outdoor unit and condense in the indoor air handler, which pumps heat into the building. Compared to electric furnaces and space heaters, heat pumps are much more efficient because they use less energy. Certified heat pumps that are Energy Star-rated use 60% less energy than electric resistance heating.

Previously, heat pumps struggled to operate effectively in extremely cold temperatures because they rely on heat from outside air, which can be challenging as the temperature drops. However, modern heat pumps are designed to operate in subzero temperatures. Even states with cold climates like Maine, Massachusetts, and Colorado are now promoting heat pumps for new home construction, according to the Rocky Mountain Institute. The latest heat pump technology is capable of performing below -10°F, but it's best to refer to the manufacturer's guidance for specific units.

Central air conditioning systems use a single outdoor condenser that is paired with one indoor air handler, whereas mini-split systems can have multiple air handlers connected to one condenser. In multi-zone mini-split systems, each air handler has its own thermostat and can cool or heat a separate space or zone.

The main advantage of multi-zone mini-splits is that they are more flexible, allowing energy to be used only where it's needed with independent thermostats in every zone. This means that unoccupied rooms can have their heating or cooling limited while keeping the occupied spaces at a comfortable temperature. On the other hand, single-zone mini-splits have limited reach since they do not have ductwork to distribute treated air, making them suitable for cooling less than 1,000 square feet.

However, installing multi-zone systems can be more complex because each air handler requires a refrigerant line set to connect it to the condenser, and the location of the air handlers can restrict the placement of the condenser since there is a limit on the length of the line set.

Recent advancements in mini-split technology have led to improvements in efficiency, with inverter compressors replacing traditional rotary compressors in many systems. The main difference between the two is that rotary compressors can only be either on or off, while inverter compressors can adjust their speed according to the heating or cooling needs of the space, resulting in improved efficiency. Energy Star has reported that Energy Star certified units with variable-speed compressors and fans can result in lower heating and cooling costs.

Ductless mini-splits have several advantages that make them an efficient option for cooling and heating. One of the most significant advantages is that they allow for independent cooling zones, enabling individual spaces within a building to be heated or cooled separately. This prevents energy from being wasted in unoccupied areas or those that are already at an appropriate temperature. This is in contrast to central systems, which must condition air throughout a building.

Additionally, ductless mini-splits are more efficient than central HVAC systems because they lack ductwork. In central air conditioning systems, over 30% of energy can be lost through ductwork, especially when the ducts are in unconditioned spaces that become extremely hot in summer.

Ductless mini-splits also have an advantage over window units and portable air conditioners in that the evaporator and condenser are separated by an insulated exterior wall, preventing heat from leaking from the hot condenser coils outside to the cold evaporator coils inside.

Finally, when used as heat pumps, mini-splits are much more efficient than other electric heaters such as electric furnaces or baseboard heaters.

Mini-split systems have several performance ratings, including cooling and heating capacity measured in BtuH, and SEER ratings to describe cooling efficiency. Higher SEER ratings indicate more efficient units, with a linear relationship between SEER ratings and electricity use over the summer. Local utility companies and Energystar's Rebate Finder may offer incentives for upgrading to high-efficiency ductless mini-splits.

Ductless mini-splits offer flexibility in terms of where the air handler can be placed. The easiest and most common installation option is wall-mounted units, which are hung high on the wall to allow the cool air to sink into the room. The refrigerant line set can exit the building through the wall directly behind the air handler, making installation and maintenance simple.

However, if clients are concerned about the appearance of wall-mounted air handlers, HVAC professionals should be aware that there are other options. For example, some units can be recessed into the ceiling or hidden with a short piece of ductwork. These options can be more complicated to install and maintain since they require cutting a hole in the ceiling and routing the line set conduit behind the drywall. Despite the additional costs associated with these options, some clients may consider them worthwhile if aesthetics are a top priority.

A ductless mini-split system positions the air handler directly inside the room it's meant to cool or heat, as opposed to distributing air through ducts from a central air handler. While a central air system only has one air handler, multi-zone mini-splits feature multiple independent air handlers.