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What is the best mini split heat pump on the market today? With winter approaching, installing a split system to regulate the temperature of your home is an excellent path to take.

However, you are going to want an efficient, energy saving unit that has the necessary power to meet your needs.

Well we’re here to help. We have selected 5 top rated mini split AC units to give you an in depth comparison on what’s currently available.

For our findings at a glance, just head to the table below. For a detailed buyer’s guide, plus comprehensive reviews of each of our selected systems, keep on reading.


Best mini split heat pump – Top 5

MINI SPLIT AC UNITNAMEDETAILSOUR RATING
TOP PICK:
Pioneer WYS012-17
Ductless, Mini Split
Air Conditioner
& Heat Pump
12000 BTU, 115V
with 9.0 hspf
efficiency
Senville SENL-09CD
Split Air Conditioner
& Heat Pump
9000 BTU, 15 SEER
Easy Installation
16 Ft. Line Included
MRCOOL DIY
Ductless Mini-Split
Heat Pump w/ WiFi
24K BTU, 16 SEER
7 Year Compressor
& 5 Year parts
Warranty
Mini Split Air
Conditioner, Inverter
Heat Pump,
AC unit.
18000 Btu, 23.3 SEER
With 15 Feet
Installation Kit
DuctlessAire
Mini Split, Heat
Pump, AC Unit
12,000 BTU, 22 SEER
Variable Speed
Inverter 220V,
25ft Kit Included

Best mini split heat pump – The Reviews

The different models, brands, and sizes of Split heat pumps in the market, can be rated using a range of variables, including performance, build quality, energy efficiency, and warranty coverage.

Using these rating criteria and more, 5 of the best ductless mini split air conditioner and heat pumps have been selected to give you the ultimate low down on which unit you should buy.

[Readers Note: there is some technical jargon within the reviews that follow, giving details of power consumption and overall efficiency of each model. A full explanation of what these terms mean can be found in the buyer’s guide after the reviews section.]

1. TOP PICK: Pioneer WYS012-17 mini split heat pump review

The Pioneer WYS012-17 is a high-quality, high-performance ductless mini split air conditioner and heat pump unit that features a humidifier and whose evaporator is designed to be mounted on the wall where it can manage the room temperature and air quality.

This energy-efficient mini-split is built using the latest HVAC technology and operates quietly and can effectively and efficiently cool or heat up any contiguous area. It comes with its installation kit.

The cooling capacity of this model is 12,000BTU/h and its heating capacity is 12,000BTU/h.

Its compressor features an inverter system which allows its refrigeration cycle to operate at different speeds which are determined by the cooling loads.

This ultra-high efficiency inverter system is powered by 110-120volts or 208-230volts, 60Hertz AC electricity.

As a AC unit, it has a SEER rating of 17.2, while as a heat pump, it has a HSPF value of 9.0.

This high-performance model is designed and manufactured by a reputable U.S-based company, Parker-Davis HVAC Systems, Inc.

This compact model is shipped as a full-set package which includes the evaporator, condensing unit, power cables, and copper pipes.

The compact and light-weight air handling unit is 31.5inches long, 7.5inches deep, and 11.5inches high.

This ductless indoor section is white in color and features an attractive front-panel and dimmable LED display.

The housing of the evaporator features automatic swing-air discharge louvers, along with permanent air filters that can be detached from the unit and washed before being reinstalled.

Inside the evaporator is a whisper-quiet and powerful fan that is operated by a variable-speed motor.

Generally, the air handling unit operates quietly, which allows one to fit it in the kids bedroom without worrying that they would not be able to catch a sleep.

The air handling unit can be operated using a wireless/remote digital controller which features a large display whose LCD back-light and superb contrast allows one to clearly see the settings of the evaporator.

This multi-functional remote features large push buttons and its infra-red capabilities allows one to send instructions immediately to the air handling unit.

This remote controller also allows the user to choose an operating mode from a list of 4 operating modes – cooling, dehumidification, ventilation, and heating.

Additionally, there is the automatic switchover mode that allows the unit to operate automatically and calibrate itself based on information it gathers from its heat and humidity sensors.

There is also a time that allows the user to set when the unit can start operating, and when to stop.

There is also the night mode which allows the air handling unit to adjust its operations based on the fluctuation of human body temperatures.

The auto-restart function allows the unit to memorize all the settings, which protects the user from losing important setting during power blackouts.

This model also comes with a WiFi-capable Smart Controller Kit that allows the user to use WiFi access for either access module or remote programming.

This programming can be done via the Cloud network which allows the user to adjust the AC unit settings from anywhere in the world.

The indoor temperature can be set anywhere between 62-90degrees Fahrenheit. For the heating mode, the outdoors operational temperature range is from 5-86degrees Fahrenheit.

This model comes with a powerful and robust outdoor unit that is 30.5inches long, 12inches deep, and 22inches tall.

This white and compact condenser unit features a durable construction made of galvanized metal that has been coated by electrostatic epoxy paint.

Likewise, its whisper-quite fan ensures that this unit operates quietly. This unit also has a single power port.

The outdoor unit comes with its mounting brackets and PVC-line cover kit.

Also, this model comes with a complete installation kit that includes a pair of 16-feet insulated copper tubings that have flare connections, wall sleeve liner, putty, interconnecting signal wiring, wrapping tape, and drain line extension.

This model weighs about 120pounds when fully set-up, and it can cover an area range of 350-450square feet. This model is approved by ETL.

The refrigerant used in this model is R410a which is already pre-charged in the condenser unit.

The Pioneer WYS012-17 benefits from a 24-month parts warranty and a 60-month compressor warranty.

Pros of the Pioneer WYS012-17 mini split heat pump
  • Very affordable when compared to other split systems
  • Reliable and energy-efficient.
  • Comes pre-charged with its refrigerant, R410a.
  • Well-designed ductless indoor section.
  • Can be operated via a wireless digital controller.
  • Supports 4 operational modes; cooling, dehumidification, ventilation, and heating.
  • Timer allows one to set start and stop times.
  • SEER value of 17.2
  • HSPF value is 9.0.
  • Heating capacity 12,000BTU/H.
  • Cooling capacity 12,000BTU/H.
  • Whisper-quiet operation.
  • 24-month parts warranty and a 60-month compressor warranty.
The Cons
  • Cannot work during power blackouts.
  • Requires professionals to install it properly.

Bottom-line

The Pioneer WYS012-17 is a high-quality, high-performance ductless mini split air conditioner and heat pump unit that features a humidifier and whose evaporator is designed to be mounted on the wall where it can manage the room temperature and air quality.

These energy-efficient mini-split is built using the latest HVAC technology and operates quietly and can effectively and efficiently cool or heat up any contiguous area measuring between 350-450square feet.

The superb performance, energy efficiency, and broad warranty coverage of the Pioneer WYS012-17 makes it, in or opinion the best buy ductless heat pump available today.


2. Senville SENL-09CD Split Air Conditioner and Heat Pump Review

The Senville SENL-09CD is a ductless mini split air conditioner and heat pump unit that can work as a low ambient kit. The evaporator is designed to be mounted on the wall where it can manage the room temperature and air quality.

As a low ambient kit, it can heat the room even when outside temperatures are as low as 5degrees Fahrenheit.

This energy-efficient mini-split unit is built using the latest HVAC technology and operates quietly and can effectively and efficiently cool or heat up any contiguous area.

It comes with its installation kit. The cooling capacity of this model is 9,000BTU/h and its heating capacity is 9,000BTU/h.

Its compressor features an inverter system made by Toshiba, which allows its refrigeration cycle to operate at different speeds which are determined by the cooling loads.

This ultra-high efficiency inverter system is powered by 110-120volts 60Hertz AC electricity. As a AC unit, it has a SEER rating of 15, while as a heat pump, it has a HSPF value of 8.5.

This high-performance model is designed and manufactured by Senville.

This compact model is shipped as a full-set package which includes the evaporator, condensing unit, power cables, and copper pipes.

The compact and light-weight air handling unit is 32.87inches long, 7.8inches deep, and 11.2inches high. This ductless indoor section is white in color and features an attractive front-panel.

Inside the evaporator is a whisper-quiet and powerful fan that is operated by a variable-speed motor.

Generally, the air handling unit operates quietly, which allows one to fit it in the kids bedroom without worrying that they would not be able to catch a sleep.

The air handling unit can be operated using a wireless/remote digital controller which features an LCD display whose back-light and superb contrast allows one to clearly see the settings of the evaporator.

This multi-functional remote features large push buttons and its infra-red capabilities allows one to send instructions immediately to the air handling unit.

This model comes with a powerful and robust outdoor unit that is 30.31inches long, 11.81inches deep, and 21.81inches tall.

This white and compact condenser unit features a durable construction made of galvanized metal that has been coated by electrostatic epoxy paint. Likewise, its whisper-quite fan ensures that this unit operates quietly.

The outdoor unit comes with its mounting brackets and PVC-line cover kit.

Also, this model comes with a complete 16-feet installation kit that contains 2 insulated copper tubings that have flare connections, putty, wrapping tape, and drain line extension.

This model weighs about 120pounds when fully set-up, and it can cover an area range of 350-450square feet.

The refrigerant used in this model is R410a which is already pre-charged in the condenser unit.

The Senville SENL-09CD benefits from a 12-month parts warranty and a 60-month compressor warranty.

This is box title
  • Reliable and energy-efficient.
  • Comes pre-charged with its refrigerant, R410a.
  • Well-designed ductless indoor section.
  • Can be operated via a wireless digital controller.
  • SEER value of 15.
  • HSPF value is 8.5.
  • Heating capacity 9,000BTU/H.
  • Cooling capacity 9,000BTU/H.
  • Whisper-quiet operation.
  • 12-month parts warranty and a 60-month compressor warranty.
The Cons
  • Cannot work during power blackouts.
  • Requires professionals to install it properly.

Bottom-line

The Senville SENL-09CD is a high-quality, high-performance ductless mini split air conditioner and heat pump unit that can work as a low ambient kit and whose evaporator is designed to be mounted on the wall where it can manage the room temperature and air quality.

As a low ambient kit, it can heat the room even when outside temperatures are as low as 5degrees Fahrenheit.


3. MRCOOL DIY 24K BTU 16 SEER Ductless Mini-Split Heat Pump w/ WiFi

The MRCOOL DIY 24k BTU ductless mini split air conditioner and heat pump unit is built for easy installation (even by amateurs). It features a humidifier and an evaporator that is designed to be mounted on the wall where it can manage the room temperature and air quality.

It comes with Apple and Android apps, which can be used to control the unit. This energy-efficient mini-split is built using the latest HVAC technology to qietly heat up or cool down your home.

Like the Senville SENL-09CD, it can heat the room even when outdoor temperatures are as low as 5degeres Fahrenheit.

It also comes with its installation kit. The cooling capacity of this model is 24,000BTU/h and its heating capacity is 24,000BTU/h.

Its compressor features an inverter system which allows its refrigeration cycle to operate at different speeds which are determined by the cooling loads.

This ultra-high efficiency inverter system is powered by 110-120volts or 208-230volts, 60Hertz AC electricity.

It has a SEER rating of 16. This high-performance model is designed and manufactured by MrCool.

Image Credit: HVACDirect.com

This compact model is shipped as a full-set package which includes the evaporator, condensing unit, power cables, and copper pipes.

The ductless indoor section is white in color and features an attractive front-panel and dimmable LED display.

The housing of the evaporator features automatic swing-air discharge louvers, along with permanent air filters that can be detached from the unit and washed before being reinstalled.

Inside the evaporator is a whisper-quiet and powerful fan that is operated by a variable-speed motor.

Generally, the air handling unit operates quietly, which allows one to fit it in the kids bedroom without worrying that they would not be able to catch a sleep.

The air handling unit can be operated using a wireless/remote digital controller which features a large display whose LCD back-light and superb contrast allows one to clearly see the settings of the evaporator.

This multi-functional remote features large push buttons and its infra-red capabilities allows one to send instructions immediately to the air handling unit.

This model also comes with a WiFi-capable Smart Controller Kit that allows the user to use WiFi access for either access module or remote programming.

This programming can be done via the Cloud network which allows the user to adjust the AC unit settings from anywhere in the world.

The indoor temperature can be set anywhere between 63-90degrees Fahrenheit. For the heating mode, the outdoors operational temperature range is from 5-122degrees Fahrenheit.

This model comes with a powerful and robust outdoor unit. This white and compact condenser unit features a durable construction. Likewise, its whisper-quite fan ensures that this unit operates quietly. This unit also has a single power port.

The outdoor unit comes with its mounting brackets and PVC-line cover kit. Also, this model comes with a complete installation kit that includes a pair of 14-feet insulated copper tubings that have flare connections, putty, interconnecting signal wiring, and wrapping tape.

The refrigerant used in this model is R410a which is already pre-charged in the condenser unit.

The MrCool DIY 24K benefits from a very impressive 60-month parts warranty and a 7-year compressor warranty.

This is box title
  • Reliable and energy-efficient.
  • Comes pre-charged with its refrigerant, R410a.
  • Well-designed ductless indoor section.
  • Can be operated via a wireless digital controller.
  • SEER value of 16.
  • Heating capacity 24,000BTU/H.
  • Cooling capacity 24,000BTU/H.
  • Whisper-quiet operation.
  • 60-month parts warranty and a 7-year compressor warranty.
The Cons
  • Cannot work during power blackouts.
  • The complete package is significantly more expensive than our number 1 pick.

Bottom-line

The MrCool DIY 24K is a high-quality ductless mini split air conditioner and heat pump unit that is built for easy installation (even by amateurs).

It features a humidifier and evaporator that is designed to be mounted on the wall where it can manage the room temperature and air quality.

It comes with Apple and Android apps, which can be used to control the unit.


4. Kaussmann 18000BTU Mini Split Air Conditioner, Inverter Heat Pump Review

The Kaussmann ETL-approved ductless mini split air conditioner and heat pump unit has a heat-extraction capacity of 1.5 refrigeration tons. It comes with its installation kit.

The cooling capacity of this model is 18,000BTU/h and its heating capacity is 18,000BTU/h.

Its compressor, made by Toshiba, features an inverter system which allows its refrigeration cycle to operate at different speeds which are determined by the cooling loads.

This ultra-high efficiency inverter system is powered by 110-120volts or 208-230volts, 60Hertz AC electricity.

It has a SEER rating of 17.6. The model is designed and manufactured by Kaussmann.

This compact model is shipped as a full-set package which includes the evaporator, condensing unit, power cables, and copper pipes.

The ductless indoor section is white in color and features an attractive front-panel. The housing of the evaporator features automatic swing-air discharge louvers.

Inside the evaporator is a whisper-quiet and powerful fan that is operated by a variable-speed motor.

Generally, the air handling unit operates quietly, which allows one to fit it in the kids bedroom without worrying that they would not be able to catch a sleep.

The air handling unit can be operated using a wireless/remote digital controller which features a large display whose LCD back-light and superb contrast allows one to clearly see the settings of the evaporator.

This multi-functional remote features large push buttons and its infra-red capabilities allows one to send instructions immediately to the air handling unit.

This remote controller also allows the user to choose an operating mode from a list of 4 operating modes – cooling, dehumidification, ventilation, and heating.

This model comes with a powerful and robust outdoor unit. This white and compact condenser unit features a durable construction made of galvanized metal that has been coated by electrostatic epoxy paint.

Likewise, its whisper-quite fan ensures that this unit operates quietly. This unit also has a single power port.

The outdoor unit comes with its mounting brackets and PVC-line cover kit. Also, this model comes with a complete installation kit that includes a pair of 15-feet insulated copper tubings that have flare connections, wall sleeve liner, putty, and wrapping tape.

The refrigerant used in this model is R410a which is already pre-charged in the condenser unit.

The Kaussmann 18000BTU benefits from a 36-month parts warranty and a 60-month compressor warranty.

This is box title
  • Reliable and energy-efficient.
  • Comes pre-charged with its refrigerant, R410a.
  • Well-designed ductless indoor section.
  • Can be operated via a wireless digital controller.
  • Supports 4 operational modes; cooling, dehumidification, ventilation, and heating.
  • SEER value of 17.6.
  • Heating capacity 18,000BTU/H.
  • Cooling capacity 18,000BTU/H.
  • Whisper-quiet operation.
  • 36-month parts warranty and a 60-month compressor warranty.
The Cons
  • Cannot work during power blackouts.
  • Requires professionals to install it properly.

Bottom-line

The Kaussmann 18000BTU is a high-quality, high-performance, and ETL-approved ductless mini split air conditioner and heat pump unit with a heat-extraction capacity of 1.5 refrigeration tons, and features a humidifier; and whose evaporator is designed to be mounted on the wall where it can manage the room temperature and air quality.


5. DuctlessAire 12,000 BTU 22 SEER Energy Star Ductless Mini Split Air Conditioner and Heat Pump Review

This DuctlessAire 12,000 BTU, is a mini split air conditioner and heat pump unit that comes with a with an energy star rating.

It features a humidifier and its evaporator is designed to be mounted on the wall where it can manage the room temperature and air quality.

Its fans have 3 speed modes, including the Turbo mode for quick warming up or cooling down of the room.

It also features leakage detection. It comes with its installation kit. The cooling capacity of this model is 12,000BTU/h and its heating capacity is 12,000BTU/h.

Its compressor features an inverter system which allows its refrigeration cycle to operate at different speeds which are determined by the cooling loads.

This ultra-high efficiency inverter system is powered by 110-120volts or 208-230volts, 60Hertz AC electricity. It has a SEER rating of 21.5.

This high-performance model is designed and manufactured by DuctlessAire.

This compact model is shipped as a full-set package which includes the evaporator, condensing unit, power cables, and copper pipes.

The ductless indoor section is white in color and features an attractive front-panel. Inside the evaporator is a whisper-quiet and powerful fan that is operated by a variable-speed motor.

Generally, the air handling unit operates quietly, which allows one to fit it in the kids bedroom without worrying that they would not be able to catch a sleep.

The air handling unit can be operated using a wireless/remote digital controller which features a large display whose LCD back-light and superb contrast allows one to clearly see the settings of the evaporator.

This multi-functional remote features large push buttons and its infra-red capabilities allows one to send instructions immediately to the air handling unit.

This model comes with a powerful and robust outdoor unit. This white and compact condenser unit features a durable construction made of galvanized metal that has been coated by electrostatic paint.

Likewise, its whisper-quite fan ensures that this unit operates quietly. This unit also has a single power port.

The outdoor unit comes with its mounting brackets and PVC-line cover kit. Also, this model comes with a complete installation kit that includes a pair of 25-feet insulated copper tubings that have flare connections, wall sleeve liner, putty, and wrapping tape.

The refrigerant used in this model is R410a which is already pre-charged in the condenser unit.

The DuctlessAire DA1215-H1 benefits from a 12-month parts warranty and a 60-month compressor warranty.

This is box title
  • Reliable and energy-efficient.
  • Comes pre-charged with its refrigerant, R410a.
  • Well-designed ductless indoor section.
  • Can be operated via a wireless digital controller.
  • SEER value of 21.5.
  • Heating capacity 12,000BTU/H.
  • Cooling capacity 12,000BTU/H.
  • Whisper-quiet operation.
  • 12-month parts warranty and a 60-month compressor warranty.
The Cons
  • Cannot work during power blackouts.
  • Requires professionals to install it properly.

Bottom-line

The DuctlessAire DA1215-H1 is a high-performance ductless mini split air conditioner and heat pump unit that comes with a with an energy star rating.

This energy-efficient mini-split is built using the latest HVAC technology to efficiently cool or heat up any contiguous area.

Its fans have 3 speed modes, including the Turbo mode for quick warming up or cooling down of the room. It also features leakage detection.


Mini split heat pump Buyer’s Guide

The mini split heat pump explained

Air conditioners are designed to provide thermal comfort in indoor spaces, as well as improve the quality of air circulating inside a room.

Air conditioners need to be installed properly in the house, building, or office complex; and one of the key installation modes is known as split systems.

In split systems, there are 2 separate components – the air handling unit and a condensing unit – that are installed in different locations and both use a common heat exchange fluid which is a refrigerant.

The air handling unit is the evaporator and it is fitted indoors. On the other hand, the condensing unit is fitted outdoors, and is made up of the compressor and the condenser.

The importance of refrigerant

Refrigerant is a very important part of the overall process. First it flows through the air handling unit where it absorbs heat from the room air.

Thereafter moves to the condensing unit where the captured heat is ejected (from the refrigerant and) into the surrounding environment (usually the atmosphere); and this process is called the refrigeration cycle.

There are specialized split systems where the refrigerant cycle is reversed so that the refrigerant absorbs heat from an outdoor heat source and then flows into the evaporator where it warms the air that is being pumped into the room, hence warming up the room.

In this instance, the room acts as the heat sink and this specialized split system is called a reverse-cycle air conditioner or a heat pump.

The different kinds of split system

There are 2 forms of split systems; the central system and the mini-split.

The central system

In the central system (also called the ducted air conditioner), the the air conditioning (AC) unit is placed at a central location inside a building with a system of ducts connecting the AC unit to the various rooms.

In this system, forced-air is relayed through these ducts and onto the AC unit where the heat exchange fluid cools down the air which is then recirculated back into the rooms.

The mini-split system

On the other hand, the mini-split system does not have ducts (hence its designation as a ductless system), and instead uses refrigerant piping to connect the air handling unit to the condensing unit.

They are therefore much smaller than the central systems, and they also allow for zoning of the house whereby a single outdoor unit is connected to 2 or more indoor units, with each indoor unit having its own unique temperature settings so that different rooms can be kept warm at different set temperatures.

The ductless mini split system

In the mini-split (ductless) AC unit, the refrigerant piping can be custom-designed to fit into the house or building, as well as connect and align well with the individual components of the AC unit.

This piping usually consists of 2 flexible lines, one for gas (gaseous refrigerant) and the other for the liquid refrigerant.

The standard system

In a standard split system schematic for a heat pump, physical separation is provided by the outside wall of a house or building which separates the indoor evaporator from the condensing unit, with the refrigerant being the working fluid that warms the house through the evaporator.

The standard evaporator consists of a coil (usually made of copper tubing), thermal expansion valve, and fan housed alongside fins (made of aluminum) that have been mounted in a steel frame.


The evaporator explained

This evaporator is the heat capture unit of the AC system where high-pressure and cold liquid refrigerant from the condensing unit goes through its tubing and into the thermal expansion valve where the liquid is throttled before it enters the evaporator coil.

Throttling causes the refrigerant liquid to lose pressure to a level lower than its saturation pressure, and consequently, the refrigerant boils inside the evaporator coil.

Boiling the refrigerant

The heat energy required to boil the refrigerant varies depending on the refrigerant type, but this energy is always drawn from whichever medium is surrounding the coil, usually air or water.

This allows the room air to be blowing through the evaporator to lose its heat to the refrigerant, and be fanned out of the evaporator as cool air.

In the heat pump, boiling refrigerant is cooled down inside the evaporator coil by the cold room air which subsequently exits the evaporator as warm air.

The 2 types of evaporators available

There are 2 types of evaporators, the flooded and the dry types.

In the flooded evaporator, the amount of liquid refrigerant in the evaporator is maintained at a constant level at all times.

Meanwhile, the dry evaporator only processes the needed/right amount of refrigerant to handle the existing workload.

For this reason, the dry evaporator is also called the direct-expansion evaporator as its expansion valve only allows a specific amount of refrigerant to enter the evaporator coil.

The chilled water system

In chilled water systems, both the dry and flooded evaporators are housed inside a shell-and-tube construction.

For the dry evaporator, water is contained in the shell (usually made of steel carbon) while the refrigerant passes through the tubes where it boils to extract heat from the water.

Meanwhile, in the flooded evaporator, a level valve is used to determine how much refrigerant is in the shell while water flows through the tubes.

Inside the shell-and-tube heat exchanger, the flow rate of the refrigerant is always throttled.

The refrigerant that leaves the evaporator is routed through the gas pipe into the compressor.

AC unit heat transfer explained

In an AC unit, heat is transferred from a low-temperature environment, also called the heat source (that is, the cool room) and into a high-temperature environment, also called the heat sink, (for instance, the sun-baked outdoor atmosphere).

This means that heat transfer occurs against a temperature gradient, and this process requires energy input to facilitate it. The compressor serves as the energy input point of the AC system.

A look at the compressor

Compressors are electrically-powered, and are driven by high-capacity electric motors which allow them to effectively draw (or suck in) the refrigerant gas from gas pipe and into the compressing unit where the refrigerant is compressed and discharged at high pressure into the condenser.

The 3 main types of compressors

The 3 main types of compressors used are:

  • the scroll type,
  • the semi-hermetic reciprocating type,
  • and the hermetic reciprocating type.

The hermetic and semi-hermetic compressors support capacity staging, which means that they can be operated at full capacity, 50percent capacity, or any other desired capacity.

The discharged high-pressure refrigerant still carries the heat absorbed from the room, as well as heat absorbed from the compressor; and is therefore described as the hot-compressed refrigerant gas.

The hot-compressed refrigerant gas enters the condenser at a high pressure, and is routed through its (condenser) coil where it dissipates heat and cools down into a cold liquid refrigerant.

This means that the condenser is the last stage of the heat exchange, with the evaporator being the initial stage.

The fan powered (air cooled) condenser

In fan-powered air-cooled condenser, heat is transferred from the refrigerant to the atmosphere, while in water-cooled condensers, heat is transferred from the refrigerant into the cooling water.

Most mini-split systems use air-cooled condensers.

In these air-cooled condensers, the condenser capacity is described as the peak load that can be effectively cooled when the surrounding atmospheric/air temperature is 115degrees Fahrenheit.

Understanding what the ratings mean

The above rating is important as the condenser capacity reduces as the surrounding outdoor/air temperature rises; and a person searching for a high-quality mini-split AC unit must check to ensure that the equipment can effectively cool the refrigerant at high ambient daytime temperatures.

On the other-hand, extremely low outdoor temperatures can drastically increase the condenser capacity hence leading to a more intense cooling that causes the cooled refrigerant to have a very low pressure that impairs its ability to move efficiently through the liquid pipe and into the evaporator.

It is for this reason that one is advised to choose a mini-split that has variable fan-speed control as it allows one to vary (or regulate) the airflow during cold seasons. Air-cooled condensers usually have copper coil construction, along with aluminum fins.

Introducing the heat pump

Image Credit: Homepower.com

The heat pump is the mini-split that can reverse the functions of the condenser and evaporator so that heat is absorbed from the outdoor air by the condenser (which now acts as the evaporator).

The refrigerant boils in the condenser coils and is then routed as gaseous refrigerant to the evaporator where it cools down in the evaporator coil as it loses heat to the room air.

This is subsequently fanned out of the evaporator as warm air while the refrigerant leaves the evaporator as a cold liquid refrigerant.

This makes the heat pump to be more energy-efficient as compared to standard electric resistance heating.

Compactness and energy efficiency

As mentioned earlier, the mini-split AC or heat pump unit is designed for compactness and energy efficiency. This is because it is built to operate as an effective thermodynamically closed system.

This means that it can only exchange heat energy with its surroundings, with matter (hereby represented by the heat-exchange refrigerant) staying inside the system at all times.

In the AC or heat pump setting, the room is considered as the system that is to be maintained at a specific temperature.

This implies that if a 200-watt heating element is turned on inside the room for an hour and the temperature rises, the AC unit is expected to remove all the (additional) heat energy created by the heating element.

To do this, it must draw electrical energy through the compressor to power the air conditioning process.

Therefore, any increase in the room temperature (which indicates energy input into an AC system) requires the mini-split AC unit to consume power so as to stabilize the system.

Power consumption Calculations

The amount of power consumed to effectively cool down the room to the set temperature determines efficiency of the AC unit.

This efficiency is calculated as the Coefficient-of-Performance (CoP) which is the amount of energy input into an AC system divided by how much power is drawn by the AC unit in order to return the AC system to its set temperature.

For example, if AC unit drew in 50watts so as to remove all the energy created by the 200-watt heating element, then the CoP is 200watts/50watts = 4.

Usually, CoP is expressed as a percentage and therefore this CoP can be calculated as 200watts/50watts X 100 = 400percent.

Therefore, the AC unit is said to have a CoP of 400percent.

Still, one needs to remember that the total power consumption is 200watts + 50 watts = 250watts, as this power is drawn from the same source.

Therefore, an AC unit with a high CoP decreases the overall energy consumption while improving the overall power efficiency of the AC system.

High efficiency

Normally, mini-split AC units operate at efficiencies greater than 100percent with mini-split heat pumps always operating at efficiencies far greater than 100percent as it delivers additional heat from the heat source to the heat sink (which is the air-conditioned room).

In the U.S, the heat-extraction capacity (or power) of an AC unit is rated in terms of refrigeration tons (RT) or tons of refrigeration (TR).

One TR is the amount of heat energy required to melt a short ton (907kilograms or 2000pounds) of pure ice (whose temperature is 0degrees Celsius or 32degrees Fahrenheit) in 24hours.

By approximation, 1 TR is equivalent to 3.5KiloWatts or 12,000BTU/h (British Thermal Units per hour).

1 BTU is the amount of heat energy that can raise the temperature of 1pound of water by 1degree Fahrenheit.

The professional body for HVAC engineers, ASHRAE (acronym for the American Society of Heating-Refrigerating and Air-Conditioning Engineers; and its predecessor ASHAE) accept the use of BTU/h as an industry standard for measuring the cooling power of AC units.

Minimum energy-efficiency requirements

Some nations have set minimum energy-efficiency requirements for mini-splits AC and heat pump units.

In the U.S, this efficiency is rated as SEER (which stands for Seasonal Energy-Efficiency Ratio) which caters for the seasonal changes of the atmospheric temperature during the four seasons of the year.

SEER is calculated as the BTU (cooling output) of the AC unit (when used normally) for a full year divided by total electrical energy consumed (in terms of watts-per-hour, W.h) that year.

Therefore, SEER = BTU/W.h, which can also be rewritten as SEER = (BTU/h)/Watts.

This means that a 12,000BTU/h AC unit with a SEER rating of 10 only consumes 12,000/10 = 1200watts on average.

If the annual operating time for this unit is 1000hours, then the total electrical energy consumed per annum is 1200watts X 1000hours = 1,200,000watts.hour = 1.2MWh.

Meanwhile, its total cooling output is 12,000BTU/h X 1000hours = 12,000,000BTU, which when divided by the SEER yields 12,000,000BTU / 10BTU/W.h = 1,200,000W.h = 1.2MWh.

Understanding the SEER value

The SEER value is related to both the CoP and the Energy-Efficieny Ratio (EER). EER describes the efficiency rating at a particular set of internal and external temperatures.

In ductless heat pump, the BTU Heating Maximum describes the maximum heating output of the unit.

HSPF (Heating Seasonal Performance Factor)

Another important rating is the HSPF (Heating Seasonal Performance Factor) which describes the efficiency of tan air-source heat pump when generating heat.

HSPF is calculated by dividing the BTU heat output with power consumption (in watt-hours) and this is mathematically expressed as BTU/W.h.

Air-sourced heat pumps also have an operating temperature which denotes the minimum outdoor temperature that the unit can properly operate in, and if the temperature outside falls below this value, then the unit loses its efficiency, especially if ice forms on the fins of its condenser and compressor.

For heat pumps, the air flow rate is important and is measured in cubic-feet per minute (CFM). A high CFM means that warm air can be circulated throughout the room within a short time.

This air flow rate is determined by the speed of fans and their operational efficiency.

However, fans produce noise and one needs to check the noise level rating of any mini-split air conditioner before purchasing it.


Image Credits: Quadomated, Halifax Heating, Homepower.com