The mini split system is both science & art in modern HVAC engineering. A ductless system that has the ability to do both cooling and heating (at extremely high efficiency) is phenomenal. We’ll dive a bit deeper on how the mini split system works.

 

We will provide you a detailed explanation of how the mini split systems can provide both cool and heat. It seems contradictory but the explanation of how this works is relatively simple. All this has to do with is the dual functionality of the compressor; it’s capable of compressing the refrigerant (cooling) as well as expanding the refrigerant (heating). Below is how the mini split works.

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• Mini splits systems are ductless. You don’t need any ductwork like central air (cooling) and furnaces (heating).

 

• The mini split system can both provide both cooling and heating. It is basically a heat pump; it pumps heat in and out of your home.

 

• It’s very high energy efficient. Mini splits typically have a 20+ SEER rating (cooling efficiency) and a 10+ HSPF rating (heating efficiency).

 

• Ductless mini split heat pumps basically pump heat from indoors to outdoors (cooling) and from outdoors to indoors (heating). The reason why they can be so energy efficient is that they don’t create heat unlike like a furnace that burns natural gas. They merely transport heat between two spaces.

 

The basic principle of how the mini split systems work is proven by its refrigeration cycle. This is a well-established thermodynamic (fancy word) cycle that uses the compression and expansion of refrigerant (R410A) to transport heat.

 

To understand how mini splits AC/heat pump works, you will need to know its 3 main components:

 

1. Outdoor Unit: this is where the most important internal part “compressor” is located.

2. Indoor Unit: this is the air handler mounted on a wall.

3. Refrigeration lines combined with signal lines.

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Here’s how the mini split air conditioner works in chronological steps:

 

1. A compressed refrigerant in liquid form (low pressure) flows from the outdoor unit to the indoor unit via refrigeration lines.

2. When liquid refrigerant arrives in the evaporator cooling coils (located in the indoor air handler), it expands and turns liquid to gas. Thermodynamically, this is an endothermic process which means that the coils are cooled during this process.

3. The indoor air blower takes in warm indoor air and pushes it over these cold coils. This event cools the air and removes the humidity as well (air moisture is condensed on these cold coils). This cool and dry air is expelled into our home. During this event, you experience the indoor air handler blowing cold air.

4. Gaseous refrigerant (high pressure) now travels back to the outdoor unit via refrigerant lines connecting the two units.

5. In the outdoor unit, the refrigerant is compressed (by the compressor) and turned back into a liquid state. This is an exothermic (fancy word, again) process which generates heating. This is why outdoor units can be extremely hot. The main job of the compressor is to squeeze all the gathered heat from this refrigerant.

6. Once the refrigerant is again in cool liquid form, it travels back into the indoor unit via refrigerant lines

7. We are again at the beginning of the mini split refrigeration cycling. This cycle repeats itself over and over again until we get to the set indoor temperature.

 

Remember, the refrigerant extracts heat from indoor air (by expansion) and pumps it outside. In an outdoor unit, the compressor squeezes all that heat out of the refrigerant, and this cycle repeats itself over and over again.

 

How Can A Mini Split Provide Heating?

 

With a traditional AC unit, the furnace provides the heating and the central AC unit provides the cooling. How do mini splits provide both cool and heat?

 

The refrigeration cycle, mentioned above, is just reversed. Mini splits use a reverse valve (special switch) that turns the flow of refrigerant around. That’s pretty much it! instead of cooling, you are now get heating.

 

While operating as a standard AC, the refrigerant is expanded indoors (providing cooling) and compressed outdoors (providing heat). When you switch the reverse valve, the mini split heat pump gathers all the available heat from outdoors and brings that heat indoors.

 

As you may have noticed, the whole point of heating is the ability of the compressor to work as an evaporator (capable of expanding the refrigerant gas).