Everything You Need to Know About Ducted Mini-Split Air Conditioners

There are many people who don’t even know that ducted mini-split ACs exist. Even when I started my career in HVAC, I thought mini-splits were only ductless. It wasn’t until 2019, when I did a ducted mini-split project for a shopping mall, that I discovered otherwise. Here, I’ll share the design and discuss that project for your reference.

A lot of people ask why it’s called a mini-split. These days, that question is harder to answer because manufacturers now make units over 5 tons (60,000 BTUs). I have worked with 10-ton (120,000 BTU) ducted mini-splits, which have similar dimensions to VRF ducted units or an AHU. However, the height of the unit is a little slimmer compared to the Air Handling Unit. In places where the ceiling height is an issue, a detected mini-split can be a good option for you. Here is the design of that project:

My first ducted mini-split project was for Comilla New Market, a local shopping mall in the city. At the time, I was a project engineer at a vendor company. Once the client approved the design, we started work. We installed all outdoor units on the rooftop and indoor units on the floors, followed by completing the copper piping, communication cables, electrical cables, flashing, pressure tests, vacuuming, refrigerant charging, and finally, commissioning.

These days, I don’t work with split ACs as much; my projects are mainly VRF and chilled water systems. Looking back, I feel VRF would have been better suited for this project than ducted mini-splits. As you can see in the design, a lot of copper piping was needed, which can make fixing leaks very difficult. With VRF, however, using Y-joints or copper branches can simplify these issues. But this example can still be useful for understanding ducted mini-split installations. Instead of using 31 ducted mini-splits as we did, for a home with only one or two units, this process could be very effective. For ductwork, we used GP sheets, but flexible ducting is another option.

Advantages of Ducted Mini-Splits:

1. Imagine your house has 5 rooms and 2 of them are small. So, each room has different requirements. Like one required 300 BTU, and another needed 600 BTU.

Now the thing is, manufacturers don’t make that many low-capacity units. In this case, the only option we have is a ducted mini-split. Because it gives us more access to get the required comfort. By using a VCD we can easily set the required CFM for room. It can be 100 CFM or 500 CFM doesn’t matter. 

We also can use a Grill with a damper. With this, we can easily move the damper and can control the airflow for every room.

2. By using ducted mini split, we don’t need to buy multiple air conditioners to control the room’s environment. Also not buying higher capacity ductless units minimizes the cost and in the long term helps us to maintain a low electricity bill.

If a room requires 300 BTU, and we use 12 BTU ductless units in that particular room then it will affect our comfort and bank balance by consuming extra electricity.

3. Lower maintenance costs (if you control multiple rooms with ducts, you only need to maintain one unit).

4. You can use an additional filter on the return grill which you can not do with a type unit. By doing this the air quality will be nice.

5.No need to install an outdoor unit for each room or an indoor unit, which helps maintain a neat exterior.

6. Faster installation time. For instance, if a house has 4-5 rooms with a total requirement of 60,000–120,000 BTUs, you could install a single indoor unit and use ducts to distribute air to each room.

7. Cost less than an Air Handling Unit (AHU) or Central ducted unit.

8. When you have a ceiling height issue in your place then ducted mini split can be a choice.

Because, although its size is almost similar to AHU and Central Ducted unit the height of this machine is less compared to them.

Disadvantages of Mini-Split ACs:

1. This kind of unit is not ideal for renters because once you want to change the house, it becomes difficult to Dismantling all the duct. 

2. 

   After long use, flexible ducts can accumulate dirt, which can lead to poor airflow. In this condition duct cleaning service is mandatory.

I don’t get it, that is why these units are not that popular, because they provide a lot of value. Maybe it is because when someone lives in a rented house and they plan to change their location then things get hard for them. In this condition, they need to dismantle the duct from their house. Which is not an easy job.

So, if you live in your personal house, then close your eyes and go for the ducted mini split.

Installation time and cost:

The installation cost is less than the ductless units, AHU and other Central ducted units. Because here you don’t need to buy individual units for each room.

But it takes more time to install compared to the ductless unit. Because it has additional ductwork. It can take two days to complete the installation process. Flexible ductwork takes less time and the GP sheet work takes more time to complete. As you can see in my shared drawing all duct was metal made. In some particular areas clients don’t want flexible ducts because, in long term use, it is less reliable compared to the metal duct

“Moven-pic” is an upcoming hotel project of mine, the design work is still ongoing for it. It will take approximately 2.5 years to complete the work. But there is a site office for us & we installed a ducted mini split for this office. It is also made of metal duct.

Maintenance cost:

Maintenance is a concern for lots of people. Well, most of the companies provide a 1/2-year service warranty for the unit. So, if you feel any technical issue then you will get the service from them. After that servicing is a problem because technicians charge very high for manpower & parts like, PCB, Rectifier, Fan-motor, Sensor, etc.

In ducted mini split AC, you have an extra pain, that is duct cleaning service. It costs very high to get this service but to prevent this issue and maintain clean air flow I suggest installing a filter in the return line of the unit.

Getting an additional filter is not that hard because you can make it from a workshop or make it by yourself.

Despite all of this, it consumes less money to maintain because you are using only one unit. If you chose 5 units for each room then the maintenance and electricity both will cost very high.

Without proper maintenance, if the evaporator and condenser get dirty it will affect the refrigeration cycle of the air conditioner. Because those two are the main part of an air conditioning system. Here the heat exchange happens and after the heat exchange evaporator makes our room cool. If it gets dirty then it will take more time to provide the required temperature.

That’s why I suggest using an additional filter. Remember that the filter needs to be cleaned in every three months.

You will find a lot of types and models on the market. It can be 1TR or 10 TR, choose the capacity as per your requirement. I hope this Blog will help you to decide your choice regarding the detected mini split Air conditioner. If you want to know more about ducted mini split then I am suggesting a wonderful video that can fulfill your desire. https://www.youtube.com/watch?v=YBE8H80dDN4