Typically, you need one mini-split system for every room in the house. However, you may also need just one multi-zone mini-split system for the entire house. It all depends on the size of the home, the sizes of the individual rooms, and the size of the mini-split system.
Indeed, you may even need more than one mini-split system for a single room if the room is too large for the first mini-split system.
How the Size of the Home Impacts the Number of Mini Spits Needed
The first thing to consider when thinking about the number (or size) of mini splits you need is the size of your home. Of course, this is assuming you’re shopping for a cooling system for the entire home.
A larger home means you need a more powerful air conditioner. But whatever the AC size, you’ll need either one multi-zone system, multiple single-zone systems, or multiple multi-zone systems.
One multi-zone AC
The number of zones will depend on the number of rooms. In fact, in most cases, the rooms are essentially the rooms. Thus, for a 5-room house, you’ll need a 5-zone mini-split system, and for a 7-room home, you need a 7-zone mini-split system.
Each room will have a separate indoor air handler. But in the end, you only need one outdoor compressor unit – thus, one mini-split air conditioner.
Multiple single-zone Mini Splits
Alternatively, you can choose to install a separate single-zone mini-split in every room. Each room gets an outdoor condenser and an indoor air handler in this approach – the two parts making a complete mini-split system.
In this case, therefore, you need several complete mini-split systems. For a 5-room house, you need five complete, single-zone air conditioners. If the room has seven rooms, you’ll need seven complete single-zone air conditioners. The number of complete mini-splits you need equals the number of rooms in the house.
Multiple multi-zone systems
In extra-large homes with more than nine rooms, you may need two or three mini-split air conditioners to serve every room. The reason is that currently, even the most powerful mini-split systems can only serve up to eight rooms.
If you need something bigger than an 8-zone system, you’ll need to combine several multi-zone systems or complement your multi-zone system with a few single-zone systems.
In both cases, you need to purchase at least two complete mini-split systems. For instance, if your home has 12 rooms, you can buy 3X4-zone systems, 4X3-zone systems, 2X6-zone systems, an 8-zone system, and a 4-zone system. Alternatively, you can purchase an 8-zone system and 4Xsingle-zone systems.
Impact of Room Size on Number of Mini Splits Needed
Although many mini-split applications are designed such that each room is effectively a separate zone, sometimes a room can be too big for a single zone.
This is more common in industrial applications where some rooms are as large as 2,000 square feet. However, you can also have a reasonably large garage in your home. Or, it could be the basement. If a room is too big to function as a single zone, you can split it into two or more zones.
You can also have different zones in a single room if different rooms serve different purposes. For instance, some homes are designed such that the dining area forms part of the living room.
In this case, it may be wise to separate the two areas into distinct zones for individualized climate control. This way, you can control temperatures in the living rooms differently from the dining area. You can lower the AC setting in the dining area during meals and raise it when you’re done to save energy.
If you decide to split a single room into multiple zones, you’ll need a multi-zone mini split system or multiple single-zone systems for the area. However, you rarely need several multi-zone systems for this type of application.
- Single multi-zone setup
With a single multi-zone system, all you need to do is make sure that the air handlers are located in the different zones. For instance, you can have a dual-zone system for your dining area + living room floor plan. This way, one air handler is installed in the living area and another in the dining area. Multi-zone systems offer individual zone control.
- Multiple single-zone units
You can also bring in multiple single-zone mini-split systems instead of one multi-zone system. So in the above example, you’d need two single-zone mini-splits – one for the living area and the other for the dining area.
Here too, the number of complete mini-splits you need equals the number of zones in the room. If you split the room into four zones, you’ll need four complete mini-split systems.
Impact of Mini Split Size on How Many Mini Splits You Need
Finally, the number of mini-split systems you need is also directly related to the size of each mini-split system. If you’re buying smaller mini-split systems, then you’ll need several of them where one large unit would’ve been sufficient.
The reason is that a mini-split AC can only extract so much heat from a given area. The average rate is 20 BTUs worth of heat per square foot. It means that a 5,000 BTU air conditioner can only effectively serve a 250 square foot area (i.e., 5,000 BTUs/20BTUs/Square Foot).
It means that for a 500 square-foot room, you need about 10,000 BTUs, and for 1,000 square feet, you need about 20,000 BTUs.
It follows, therefore, that you need 2X10,000 BTU mini-split systems for a 1,000 square-foot area. However, if you can only find 7,000 BTU mini-splits, then you’ll need three for your 1,000 square foot room.
The problem is further complicated by the dangers of over or under-sizing your air conditioner. Both extremes come with consequences;
- Oversizing the AC
An air conditioner that’s too big for your room/house can cause short cycling, a risky condition where the AC doesn’t run the full cooling cycle. Short cycling can damage the AC. It causes frequent restarts that accelerate wear and tear. It also causes unnecessary noises and can increase energy consumption.
- Under-sizing the AC
An air conditioner that’s too small for the application is just as bad. First off, it forces that air conditioner to work harder and for longer. This can take a toll on your mini-split. Worse still, it may not keep you cool enough.
Therefore, you must find the right size air conditioner for the application. In circumstances when you can’t find one mini-split of the right size, you may be forced to purchase two (or more) units that, together, can deliver the amount of BTUs needed for the application.
It’s a Matter of Choice
Most people prefer to buy a single-zone mini-split system if dealing with just one room and a multi-zone system when dealing with a home with multiple rooms or a whole house.
However, you can also purchase multiple single-zone units, each for a different room in the house. Or, you may even purchase a couple of multi-zone systems for the entire home.
If you’re feeling even more confused now than when you started, you’re not alone. Many first-timers find air conditioner sizing more complex than they first imagined. The good news is that you can always retain the services of an HVAC pro.