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How Wall-Mounted Mini Splits Work

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Interesting information: Wall mounted heat pump

How a Wall-Mounted Mini Split Works?

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  • A mini-split (also known as wall-mounted) heat pump (or air conditioning) is a scalable, reliable, and energy-efficient system that allows you to manage temperature levels in your home.

    While initially conceptualized to cover individual rooms or areas of a home, increased BTU power and energy efficiency allows a mini split heat pump to cool and heat entire dwellings with one single compressor.

    Components of a mini split

    Wall-mounted heat pumps consist of two essential parts: the indoor air-handling unit (indoor head, evaporator) and the outdoor compressor (condenser). There is also a drain line, electric line and refrigerant lines that need to be installed.

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  • 1. One or more indoor air-handlers

    • The indoor head section of a mini split is essential because it directs the hot and cold air throughout the required space. The air-handler can be used to heat and cool a single room, but it can also effectively cover an entire house if it is coupled with a powerful enough compressor and is adequately located.
    • The indoor heads can vary in their look and design, but always come equipped with different sensors that allow it to measure your home’s temperature and direct airflow efficiently, among other features. For instance, direct or indirect airflow can be achieved through different settings that guide the indoor head’s vanes. This allows you to control the airflow away from or toward the occupants of the area.
  • 2. Outdoor compressor

    • The compressor is the engine of your mini split. It is responsible for compressing and circulating the refrigerant through the machine which ultimately allows you to control the temperature and comfort levels inside your home.
    • There are a few different types of refrigerant, but they all absorb and release heat that circulates between the compressor and the indoor air handler. This ensures that the indoor temperature remains at a temperature of your choosing.

    Double-stage versus single-stage compressors

    • Mini Split heat pumps and air conditioners have either single-stage or double-stage cooling.
    • Single stage cooling systems are those with a compressor that only has one level of air output.
    • Double-stage cooling systems, as their name suggests, are those with a compressor that can produce two different levels of air output. Days with more extreme temperatures will require the compressor to function at the full stage, but on most days, comfort can be achieved with the lower setting of air output. It is important to note that a double-stage compressor allows the whole mini split to produce more evenly distributed temperatures throughout the home as well as being able to run for longer periods.
    • Most of the efficient heat pumps installed by AirGreen are double-stage systems because they operate more efficiently and more silently. They are also much more effective at dehumidifying and air purifying than their single-stage counterparts.
  • 3. Condensation drain line

    • All wall-mounted systems inevitably generate a considerable amount of condensation while turned on. There is an evaporator coil in the air handler that receives the condensation and redirects the water into a condensation pan usually located in the lower part of the indoor head.
    • Once the condensation accumulates in the condensation pan, the drain line comes into play. There is a drain line that goes from the indoor unit toward your home’s drainage or directly outside. Ideally, the condensation drain line is directed downward in the walls to let gravity do the work. AirGreen technicians will always search for an optimal way to install a gravity drain line to avoid any extra components or parts that could malfunction or break.
    • In the simplest cases of wall-to-wall installation, meaning the air handler is placed on an external wall on the other side of which lies the compressor, the drain line is directed straight down the side of the house.
    • When the condensation drain line cannot be placed in a downward line, there is sometimes the need for a condensate pump that will be used to pump the water into an area where it can properly drain.
    • Since the amount of water that is drained is not very large, it is not necessary to use your home’s main drain, although it is sometimes easier to direct the drain line to the main drain than to an exterior wall.
    • While this is not necessarily a component of the mini split that clients will always think about, it is essential to install it properly. If not, you will find yourself with a nasty leak coming from the indoor air handler and ruining your walls or ceiling.
    • We recommend that you always check your municipal code requirements to make sure the installation complies with your local regulations and requirement.
  • 4. Refrigerant lines

    • The refrigerant lines are two small pipes made from copper that are used to connect the indoor air handler with the outdoor compressor.
    • There is always a larger and a smaller copper line. There are different dimensions of refrigerant lines that exist. This can be important when replacing a mini split heat pump with pipes running through many walls and floors of a building. In such cases, it is useful to know the dimensions of the current mini split refrigerant lines in order for HVAC contractors to install a new system that uses the same pipe dimensions.
    • The smaller refrigerant line is sometimes referred to as the liquid line. It is usually not insulated. It contains a warm liquid.
    • The larger line is called the suction line, but it can also be referred to as a vapor line or a return line. It must be insulated because it carries a gas.
    • The refrigerant is a liquid substance that allows the system to cool and dehumidify the air.
    • Different types of refrigerants are used by different models of mini splits. Newer and more efficient heat pumps use newer types of refrigerant that are friendlier with the environment, but also make the heat pump more efficient and are therefore friendly on homeowners’ wallets. New and improved refrigerants translate to increased energy efficiency, increased reliability, and quieter functioning of the mini split.
  • 5. Electric lines

    • The electric wires must be adequately installed for safe and reliable operation of the system.
    • The power runs from the electrical service panel to the outdoor compressor.
    • Different mini splits will have different electrical requirements. The BTU capacity of the machine will require more or less power. Typically, mini splits require at least 220 volts. Some 12 000 BTU or less powerful air conditioners may only require 110 volts, but heat pumps usually require 220 volts.
    • Different mini split models also use different thickness of electric wires (also known as wire gauges). Using the wrong wire gauge can represent a serious safety and hazard.
    • There is also a disconnect box that must usually be installed close to the outdoor compressor. Having a disconnect box allows for HVAC technicians to service the system safely by shutting off the power.
    • The condensation drain line, electric line and refrigerant line sets are usually wrapped together so that they can easily pass through a 3.5-inch diameter space through the walls and between the indoor and outdoor units.

  • Benefits

    There is no doubt that mini split heat pumps and air conditioners possess a multitude of benefits for homeowners in Quebec. They give your home strong heating and cooling with the simple touch of a button and are growing in popularity in residential as well as commercial units due to their simplicity and convenience.


    1. Simple installation


    • If any homeowner is considering installing an energy efficient source of heating and cooling, they will often have to decide between central and mini split systems. The latter option is often chosen because it is more straightforward and cost-effective than the former. Indeed, unlike central systems which require the installation of ductwork around the home, mini split systems don’t require ducts and are thus less disturbing and less expensive to install.  Mini split systems usually only require a 3.5-inch diameter hole through a wall and/or space between walls through which the refrigerant, drain, and electric lines can run.
    • Mini split systems are convenient solutions for new homes and new constructions, but they represent also a wonderful solution to improve homes that don’t use central heating and cooling systems. A mini split can be installed in a room or an area where extending a house’s ductwork is too complicated or costly. Small apartments also benefit from the simplicity of the mini split.


  • 4. Remote Control

    • As our homes become more efficient and advanced, there is no reason for comfort levels related to temperature not keep up with the times. Many of our recent mini split systems can be equipped with WiFi wireless technology that allows you to control your heating and cooling remotely from your smartphone. You can set timers, modify the desired temperatures, be notified when the system has been left turned on with nobody home, etc.
  • 2. Energy Efficiency

    • Since mini split units take air from within a room, they are particularly effective machines when it comes to heating and cooling. This efficiency quickly translates into considerable energy bills savings from any household that installs a modern efficient mini split. For Montrealers and Quebecers, heat pumps bring considerably more savings than their equivalent air conditioners. Why spend money on costly heating when a mini split can heat your home for most of the winter season?
    • This increased energy efficiency allows us to provide you with systems that can ensure your home’s comfort almost all year long. Subsidized EnergyStar systems will typically be able to function until extreme winter temperatures such as -25°C or -30°C. You can ensure your home’s comfort and relieve your energy spending as well as helping Quebec and Canada reach its long-term sustainability goals.

    3. Comfort meets style

    • Over the years, mini split have evolved to become powerful sources of heating and cooling, while also reducing their energy consumption. The aforementioned increase in energy efficiency means that new mini split systems are more silent and more sleek than ever before. Mini split systems require no ducts throughout your home. This makes them a comfortable solution to your energy needs. You don’t need a large basement or mechanical room to undertake a mini split installation.
    • The simplicity of installing a smaller outdoor compressor and an even smaller indoor makes mini split systems more subtle than central systems that take up more space and usually require a larger attic or basement space to install indoor units and ductwork.
  • Disadvantages

    1. Investment cost

    We are well aware that installing a mini split is not cheap. But this disadvantage has several solutions. Firstly, if possible, it is crucial to take advantage of one or several of the grant and subsidy programs that give Canadians and Quebecers money to ease the burden of installing a ductless mini split. You should also note that the upfront cost will be compensated by yearly savings in energy costs.

    2. Proper installation

    As a solution to the cost, some homeowners consider buying a system and installing it themselves or with a trusted person. In general, however, much like a central system, mini splits should be installed by professional and trained technicians. It is essential to have a team of certified installers to benefit from the government grants and often to have valid warranties on the installation. If you forego professional HVAC installation, you may find yourself with a headache if any issues arise with the system.

    For more information on the advantages and disadvantages, see this article on the advantages of mini split heat pumps.