A single-package mini-split system can cool up to eight rooms at a go. However, one outdoor condenser can connect to four indoor air handlers at most.
So, why do we say that a single package mini-split system can cool up to eight rooms at a go?
Because a few manufacturers have found a way to design mini-split systems that combine two condenser units into one package. With each condenser connecting to up to four air handlers, the dual-condenser mini-split packages can simultaneously cool up to eight rooms.
It’s important to note that this doesn’t mean that a condenser will always cool four rooms. Even a condenser designed for four zones may serve just one room.
It’s multi-zone, not multi-room
Sometimes when people hear “multi-zone,” they automatically relate it to rooms. A multi-zone mini-split system is designed to serve two or more zones, not two or more rooms. The said zones could be in the same large room or two rooms.
You can run it at half capacity sometimes
Though a 4-zone mini-split can connect to up to four indoor air handlers, you’re not always obligated to connect all four units. For example, you could decide to connect just three air handlers to serve three rooms/zones and leave the fourth port unused.
How a Multi-Zone Mini Split Works
As we’ve mentioned, a multi-zone mini split system comprises one or more compressors and two or more air handlers.
In single-compressor configurations, the outdoor unit can connect to two, three, or four indoor air handlers. If it connects to just one air handler, it stops being a multi-zone system and is instead referred to as a single-zone mini-split system.
In dual-compressor configurations, each compressor can connect to up to four indoor air handlers. Therefore, in total, the two outdoor units can connect to up to eight indoor air handlers.
However, you can connect each compressor to just three indoor air handlers to create a 6-zone mini-split system. You can only create a 5-zone system from the configuration.
The working is the same as any mini-split system. The indoor air handler contains evaporator coils cooled with refrigerant. When warm air blows over these coils, the heat is extracted and absorbed by the coils. Refrigerant lines running through the wall then transfer this heat to the condenser, which dumps the heat outside.
The only difference is that a multi-zone mini split (also known as multi-split) has multiple indoor air handlers. Each air handler operates independently. Each has an evaporator coil and a blower system. The blower system draws stale, warm air into the air handler via one set of vents and blows out cool, conditioned air via various vents.
Each air handler also connects to the outdoor condenser via a different set of refrigerant lines. The heat extracted from indoor air is sent to the condenser for dumping, and the cool refrigerant returns indoors and flows through the evaporator coils to capture more heat.
It’s a process that goes on and on until the thermostat temperature is achieved. Once the thermostat setting is reached, the air handler cycles on and off to maintain that temperature.
Independent BTU ratings
Each air handler has a specified BTU rating, i.e., the amount of heat it can remove per hour. For example, a 12,000 BTU air handler will remove 12,000 BTUs worth of heat from the room it’s located, and a 6,000 BTU air handler will eliminate 6,000 BTUs of heat where it’s located.
Also, each air handler comes with an independent thermostat. Most configurations include onboard (built-in) thermostats. However, a few models arrive with wall-mounted thermostats that you must install separately.
Whichever the case, an independent thermostat means you can control each air handler independently without affecting the cooling process in the adjacent zone or room. For instance, you can turn off air conditioning in one room and keep things running in the next room.
Multi-zone mini-split systems also come with independent remote controls. If it’s a 4-zone system, you’ll find four remote devices in the package. If it’s a 7-zone system, seven remote controllers are included.
This further advances the concept of independent control. If you select Turbo on the bedroom remote, only the bedroom air handler will run on Turbo mode. The other air handlers in other rooms remain unaffected.
The Number of Zones Directly Impact Cooling Capacity
The number of zones has a huge impact on mini-split capacity ratings (in BTUs). Traditionally, lower-capacity mini-split systems are reserved for single-room applications.
For example, very rarely will you find a single-zone air conditioner rated at 48,000 BTUs. Instead, most single zone mini splits are rated 9,000 BTUs to 18,000 BTUs. Meanwhile, nearly all multi-zone split systems are rated 24,000 BTUs or higher.
Outdoor Condenser vs. Indoor Air Handler BTU Ratings Can be Confusing
You may have already experienced this if you’ve shopped around for multi-zone mini split air conditioners before. Sometimes the outdoor condenser BTU rating doesn’t equal the sum of the indoor air handler BTU ratings.
Take an example of the ACiQ Stealth IntelliHeat 5-zone ductless mini-split air conditioner. The outdoor condenser is rated 48,000 BTUs. However, the package arrives with five indoor air handlers rated as follows;
- The first one is 9,000 BTUs
- Three are 12,000 BTUs each
- The last one is 18,000 BTUs
When you add the five, you get 63,000 BTUs!
What does it mean? How can a 48,000 BTU mini split AC system have air conditioners potentially reaching 63,000 BTUs? There are three explanations;
Some condensers can run beyond capacity when need arises
For instance, the 48,000 BTU-rated ACiQ IntelliHeat can perform to 63,000 BTUs for a limited period when necessary. For instance, if you’re arriving home and it feels sweltering hot, the AC may allow you to get a few extra BTUs of cooling (beyond capacity) for a limited period before you revert to standard cooling rates. In most cases, the manufacture will indicate how long you can run the AC above capacity.
We rarely run all air handlers at full capacity, all the time
Often, you only need all the air handlers running at full capacity at the beginning of the air conditioning cycle. Once you’ve reached the selected thermostat setting, you’ll mostly run the AC at 50% to 75%. It allows the manufacturer to recommend larger air handlers without adverse consequences. Remember that sometimes the air handler is off altogether in some rooms.
It’s not a fixed choice; you have the final say
Finally, you’ll realize that multi-zone mini-split configurations where the combined BTU rating of the air handlers is higher than the condenser rating allow you to pick other air handlers of your choice. For instance, the ACiQ IntelliHeat air conditioner above gives consumers the option to choose from 9,000 BTU, 12,000 BTU, and 18,000 BTU air handlers. If you’re not comfortable with the 9+12+12+12+18 configuration, you can go for 9,000+9,000+9,000+9,000+12,000 = 48,000 BTUs. It’s your choice.
A mini-split system can cool up to four different rooms or zones at a go. However, modern dual-condenser mini-split systems can cool up to eight rooms or zones at a go.
Also, only multi-zone mini-split systems can serve two or more zones. Single-zone configurations can only cool one room at a go.