A branch box is a refrigerant distribution component used in certain Mitsubishi multi-zone ductless and VRF systems. Instead of running separate refrigerant lines from the outdoor unit to each indoor unit, the branch box acts as a central connection point.
It receives refrigerant from the outdoor condenser and distributes it to multiple indoor units.
Why Is a Branch Box Used?
A branch box is used to:
1. Distribute Refrigerant Efficiently
It splits refrigerant flow from one outdoor unit to multiple indoor air handlers.
2. Reduce Line Set Complexity
Instead of multiple long line runs from the outdoor unit, installers can run a main line to the branch box and then shorter lines to each indoor unit.
3. Enable Simultaneous Heating & Cooling (on certain models)
In Mitsubishi systems with heat recovery technology, branch boxes allow different zones to operate in heating and cooling at the same time.
4. Improve Installation Flexibility
It allows indoor units to be installed in different areas while maintaining proper refrigerant control.
5. Centralize Connections
Service access is cleaner and more organized compared to multiple direct outdoor connections.
What Sizes Are Available for Mitsubishi Units?
Mitsubishi branch boxes are sized based on the number of indoor zones they support.
For systems such as the MXZ Series (multi-zone residential systems), typical configurations include:
Residential Multi-Zone (MXZ Series)
-
2-port branch box
-
3-port branch box
-
4-port branch box
-
5-port branch box
-
6-port branch box
-
8-port branch box (used with larger systems like MXZ-8C60NA)
Commercial VRF (CITY MULTI Systems)
For larger commercial applications, Mitsubishi offers:
-
4-port modules
-
6-port modules
-
8-port modules
-
Modular expansion boxes for larger systems
The exact branch box required depends on:
-
Outdoor unit model
-
Total system capacity
-
Number of indoor units
-
Whether the system supports heat recovery
When Is a Branch Box Required?
A branch box is required when:
-
The outdoor unit supports multi-zone configurations that use centralized refrigerant distribution
-
The system includes heat recovery capability
-
The manufacturer specifies it for the selected outdoor model
Some smaller multi-zone systems do not require a branch box and instead allow direct connections from the condenser to each indoor unit.
