Importance of Using the Correct Mini-Split System


Mini-splits are a great alternative to central air. They are compact and flexible for zoning individual rooms. However, it is important to use the correct mini-split system or else, they will end up giving you trouble.

To understand the importance of using the correct mini-split that matches your needs, we must tackle different aspects. The first and the most important aspect is the correct capacity. Secondly, we'll be discussing heating using the mini-split system. Then, we have the single zone versus the multi zone mini split system and finally, facts about the mini-split system that you must know.

In this article, I'll break down and explain each aspect. I hope that this helps you to understand the importance of using the correct mini-split system and thus, make a better decision.

Check out my article what is split air conditioner if you are not very clear with the mini-split system. I made a table of the mini-split vs central air. It gives you an overview of the mini-split system.

Mini splits have many different brands and models. I spent many hours researching all kinds of mini splits just to find out which one is the best. Check out the result in my post 7 Best Ductless Mini Split Air Conditioners.

Importance of Using the Correct Mini-Split Capacity

Using the mini-split system gives you great benefits. But, if you use the incorrect size mini-splits, you are left with only trouble, let alone the benefits. Following are 3 examples of the benefits of using the correct size mini-split system versus what happen if it is the wrong one.

Spend Less (Correct) vs Spend More (Incorrect)

If you extended your house and have an extra room, using the mini-split saves you from the cost of modifying the existing ductwork. However, installing the wrong size mini-split will cause you to spend more to upgrade it.

Modification of existing ductwork is very messy work and is also very costly to do. Meanwhile, installing a mini-split in the additional room is a wise choice. After all, you don't have to cut the ceiling which requires you to shift the furniture or cover them up to avoid dust from settling on them. Besides, the mini-split only requires a small 3 inches hole through a wall for the refrigerant pipe and electrical conduit.

However, if you installed an undersized mini-split, you can't have sufficient cooling or heating in the room which in turn needs you to either install more mini-splits or upgrade the mini-split. Whichever it is, you end up spending more and perhaps, more than the cost of modifying your existing ductwork.

Energy Saver (Correct) vs Energy Sucker (Incorrect)

For an apartment room, a window air conditioner often is the cheapest solution for thermal comfort. But, a mini-split has higher efficiency and thus, it consumes lesser electricity. However, if you use the wrong mini-split, you may end up paying more for the electricity bill every month.

Window air conditioners are more affordable than mini-splits but they are not very efficient. It is especially noticeable during the summer. On the other hand, mini-splits consume 30% less electricity than other room air conditioners including window air conditioners and portable air conditioners.

ChillWell AC Product Review
ChillWell AC Product Review

However, if you use an oversized mini-split, it'll provide too much cooling that uses extra power which is unnecessary. Your mini-split will suck the juice out of the electrical line like never before. Not only that you have to pay more for the electricity usage, but you also can experience what it is like staying inside a refrigerator.

Climate Under Control (Correct) vs Climate Out of Control (Incorrect)

Most of the time, central air conditioners are not able to provide individual room temperature control. Furthermore, they are not good in maintaining a precise temperature throughout the day. Meanwhile, the mini-split system allows you to control room temperature independently and precisely.

Central air conditioners usually can't provide precise temperature and humidity control because they don't use inverter technology. Although some of the new central air conditioners are inverter type, almost all mini-splits are inverter type. Thus, they provide excellent temperature and humidity control.

Check out my article are inverter worth the price if want to know more about inverter technology and how it can help you to save money and sleep better.

Whether or not your air conditioners have inverter technology, it doesn't matter when they are oversized or undersized. Even with the inverter technology, oversized mini-splits are not able to reduce the humidity to a comfortable level because they cool too quickly. Similarly, undersized mini-splits are not able to provide sufficient cooling on hot days.

Get to know what size air conditioner do you need using the my ACROT map no matter where you live in the world. Different climates require different size air conditioners. The ACROT map was developed for global use.

Importance of Using the Correct Mini-Split for Heating

There are two types of mini-split systems; a) cooling only mini-splits, and b) mini-split heat pumps (cooling and heating). As the name suggests, cooling only mini-splits, which is often called mini-split “air conditioner”, are not able to provide heating, even when you set the temperature at 86°F (30°C) or maximum.

To use a mini-split as a heater, you must pick a mini-split with a heating function (called heat pump) that has a reversing valve to reverse the refrigeration cycle which in turn gives you heating instead of cooling. The mini-split heat pump will harvest the heat from the ambient air, amplify it and transfer the heat into your house.

However, typical mini-split heat pumps can't work effectively when the ambient temperature approaching 32°F (0°C). Some of them are able to continue working for as far as -13°F (-25°C) at a lower percentage of their rated heating capacity. Meaning, you'll start to feel cold as the heat pump struggle to provide sufficient heating when the outside temperature drop below 32°F (0°C).

Hence, if you are living in a cold climate where the ambient temperature will fall beyond the freezing point of water, mini-split heat pumps are not suitable for you. Though you may add space heaters to support the heat pump, I don't recommend doing so because heating in the winter is life and death.

Importance of Using the Suitable Type of Mini-Split Indoor Unit

There are several types of indoor unit you can choose from the mini-split system. Each type has its own unique characteristics. Following are the 4 common types of mini-split indoor unit:

1. Wall Mount: All Rounder

The wall mount is the most common type of mini-split indoor unit. It is suitable for most houses with standard rooms. It is installed up high on the wall, usually at about 7-8 feet height. However, it needs to be installed at about 2-4 inches below the ceiling (if you have one) to allow space for good return air. It is suitable for apartments, flats, rented rooms and windowless rooms.

2. Floor Mount: Handle Low Ceiling Height

The floor mount is a type of mini-split indoor unit commonly used to handle low ceiling rooms. However, it also can be used in a high ceiling room. It is placed on the floor but needs to be secured onto the wall. It discharges air upward, much like a portable air conditioner and returns air from the front, just like a window air conditioner. It is suitable for tiny houses, mobile houses and attic rooms.

3. Ceiling Cassette: For Square-Shaped Room

The ceiling cassette is a type of mini-split indoor unit more suitable for large square-shaped rooms. It is usually installed above the ceiling with its front panel exposed below the ceiling, flushing with the ceiling. However, it can be installed without the ceiling too. It is best to be placed at the center of the room because it distributes air in four different directions. It is suitable for the living room and master bedroom of large houses.

4. Ceiling Concealed: For Large Rectangular-Shaped Room

The ceiling concealed is a type of mini-split indoor unit basically a small ducted unit. It is more suitable for large rectangular-shaped rooms. It is concealed completely above the ceiling. It is usually placed at the end of the room and distributes air through ducts and diffusers. It often can be found in the living room, dining room and hallway of large houses and mansions.

Single Zone Mini-Split vs Multi Zone Mini-Split

The single zone mini-split system has one indoor unit and one outdoor unit. Meanwhile, a multi zone mini-split system can have 2-4 indoor units and a single outdoor unit. The outdoor unit of the multi zone mini-split system is more powerful and physically larger than the outdoor unit of the single zone system.

Check out my article what is multi split air conditioner if you are not familiar with the multi zone mini split system. Not many people understand the actual working principle of a multi split air conditioner especially with the capacity sharing mechanism.

Following is a table of comparisons between the single zone and multi zone mini-split systems to give you an overview of what's their differences. I use the Japanese brand, Daikin, as an example for the comparison.

Single ZoneMulti Zone
BrandDaikinDaikin
SeriesAuroraAurora (Indoor Unit)
Emura (Outdoor Unit)
Number of Indoor Unit12 to 4
Number of Outdoor Unit11
Indoor Unit Capacity
(Cooling)
9,000 to 21,200 btu/hr9,000 to 18,000 btu/hr
Indoor Unit Capacity
(Heating)
10,900 to 24,000 btu/hr9,000 to 18,000 btu/hr
Outdoor Unit Capacity
(Cooling)
9,000 to 21,200 btu/hr18,000 to 34,400 btu/hr
Outdoor Unit Capacity
(Heating)
10,900 to 24,000 btu/hr18,900 to 36,600 btu/hr
Energy EfficiencyUp to 20.3 SEER
Up to 12.5 HSPF
Up to 21.7 SEER
Up to 12.5 HSPF
Data Source: Daikin North America

While the multi zone mini-split system has a larger capacity, its indoor units are only available from 9,000 btu/hr up to 18,000 btu/hr, much like the single zone mini-split system. However, the energy efficiency of the multi zone mini-split system is higher than the single zone mini-split system.

The single zone mini-split system is suitable for almost anyone. Although you may end up with several outdoor units, they are not so bad looking when installed at equal height and space. However, if you don't have space for so many outdoor units, you can opt for the multi zone mini-split system.

This many of outdoor units is crazy, should have use the multi zone system.

12 Facts about the Mini-Split System You Must Know

You may know the benefits of the mini-split system, but you may not know that the mini-split system comes with restrictions. If you are not using the correct mini-split system, you'll end up with costly troubles.

1. Definition of the Mini-Split System

The mini-split system is made up of two separate units; the evaporator and the condenser. The evaporator is installed inside the house while the condenser is installed outside the house. Both units are connected by a set of refrigerant pipes to transfer the heat from indoor to outdoor. Thus, the evaporator is often called the indoor unit and the condenser is often called the outdoor unit.

2. One Single Zone Mini-Split Has One Outdoor Unit

For a single zone mini-split, you need to have an outdoor unit for each indoor unit. The outdoor unit of the mini-system is often side discharged. Hot air transferred from the indoor unit to the outdoor unit is discharged sideways rather than upward, unlike most of the central air outdoor unit. They are much smaller and lighter than the outdoor unit of the central air conditioner.

3. Mini-Split Outdoor Unit Can Be Floor Mounted and Wall Mounted

The mini-split outdoor unit can be floor mounted on a concrete slab or a galvanized steel bracket. More often, they are hanging on the exterior wall, back-to-back with their respective indoor unit which minimizes the refrigerant pipe length and thus, reducing the cost.

4. Mini-Split Outdoor Unit Can Be Installed Far Away from Its Indoor Unit

A mini-split outdoor unit can be installed as far as 50 feet away from its indoor out in terms of the total refrigerant pipe length. As for the height difference between the outdoor unit and its indoor unit, it is usually around 30 feet. The outdoor unit often must be installed lower than its indoor unit.

5. Mini-Split Outdoor unit Need Space Clearance

Several inches of space clearance around the outdoor unit must be allowed for a good flow of air to prevent a hot air short cycle from happening which can stop the operation of the outdoor unit. Generally, the outdoor unit should be located at a well-ventilated place.

6. Cooling Only Mini-Splits Doesn't Provide Heating

There are two types of mini-split systems; a) cooling only, and b) cooling and heating. Hence, be aware of it when you are shopping for a mini-split. Usually, mini-splits with both cooling and heating functions are called heat pumps. Furthermore, look for a heat mode to confirm if the mini-split that you are eyeing has a heating function.

7. Multi Zone Mini Split System Can Pair with Different Types of Indoor Unit

The multi zone mini split system can pair with different types of indoor unit such as wall mount, floor mount, ceiling cassette and ceiling concealed. Based on your needs, you may pick the ceiling cassette for the living room, wall mount for the bedroom and floor mount for the basement.

8. Mini-Splits are Sized By Room Rather Than Whole House

While most central air conditioners are sized based on the square footage of the entire house, mini-splits are sized individually by room even for the multi zone mini-split system. The capacity of mini-splits is according to the area of each room in your house. Usually, the total capacity of mini-splits is lower than central air conditioners given the same square footage.

9. Mini-Split Heat Pumps Doesn't Work When the Weather is Too Cold

Most mini-split heat pumps don't work when the outside temperature drops below 32°F (0°C). When the weather is too cold, heat pumps are not able to extract any more heat from the surrounding air and thus, they will stop working. So, keep in mind that if your area is very cold in the winter, mini-split heat pumps are not suitable.

10. Oversized Mini-Splits Can't Provide Proper Humidity Control

Just like any other air conditioner, oversize mini-splits can't reduce the humidity of the air to a comfortable level. So, make sure you don't install an oversized mini-split in your room. Otherwise, your room will end up feeling like a refrigerator; cold and clammy. Furthermore, oversized air conditioners consume more electricity.

11. Undersized Mini-Splits Can't Cool Properly on Hot Days

Just like any other air conditioners, undersized mini-splits can't cool properly on hot days. Having an undersized air conditioner in your room may not feel any different during normal days. When it comes to hot days, the undersized mini-split will struggle to bring down the room temperature. Moreover, undersized air conditioners often have a shorter lifespan due to constantly working at maximum load.

12. Inverter Mini-Splits Can Operate at Different Capacity

Inverter mini-splits have an inverter drive that manipulates the electrical frequency of the compressor which in turn, controls the compressor's speed and thus, regulates capacity based on the requirement. Don't worry if your room is too small for a 9,000 btu/hr mini-split because an inverter mini-split can operate anywhere between 4,400 and 10,200 btu/hr (that's right, overclock!).

Conclusion

It is important to match the correct mini-split system to your needs. Everyone has their own needs and preferences. Thus, the best way to know which one is suitable for you is to understand it which is what I've written above. However, you don't need to know everything about the mini-split system but those that will make a significant impact.

Nevertheless, you can always pay an HVAC contractor and have them assess your house and give you suggestions. But, be skeptical when they push a ducted air conditioning system to you because chances are, they want to make more money from you.

Lastly, I hope this article is helpful to you and I look forward to your next big purchase which I believe you shall make a better decision now. The mini-split system is a great air conditioner with high energy efficiency. When using it correctly, less energy is consumed and therefore, making the world a better place.


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Yu Chang Zhen

I enjoy working on air conditioners and ventilation fans because Malaysia is a very hot country.

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