Addressing Limits on Fujitsu VRF Indoor Units

In Fujitsu VRF (Variable Refrigerant Flow) systems, proper addressing is the backbone of system communication. A common pitfall during large-scale commissioning is exceeding the logical boundaries of the system’s internal mapping.

The "Hard Cap" Rule: Address 64

When configuring Indoor Unit Addresses (IU AD), the highest allowable address is 64.

While the rotary switches or service tools might physically allow you to input a higher number, the system’s central controllers and Service Tool software are architected to recognize a range of 0 to 64.

Why This Is Deceptive

Exceeding address 64 creates a "silent failure" scenario that can be difficult to troubleshoot:

No Error Codes: The indoor unit will often power up and may even operate based on local thermistor data or a simple remote controller.
Control Blindness: The unit will not appear on the System Controller, Central Remote Controller, or any network-based service tools.
Command Failure: Because the central bus doesn't "see" the address, it cannot send setpoint changes, mode shifts, or scheduling commands to that specific unit.

Technical Configuration & Verification

1. Manual Addressing (Rotary Switches)

Most Fujitsu VRF indoor units use two rotary switches to set the IU AD:

REF AD (Refrigerant Address): Typically represents the outdoor unit/system loop.
IU AD (Indoor Unit Address): The specific identifier for the fan coil.

2. Electronic Addressing

If using a Function Setting via a wired remote controller or a Service Tool, ensure the data value entered for "Address" does not exceed 64.

Marksman’s Precision Tip: Always document your addressing map on the "As-Built" drawings. If you have 70 units on a single VRF network, you cannot simply address them 1-70. You must split them into separate communication segments or systems to stay within the 0–64 limit.

Troubleshooting "Invisible" Units

If you have a unit that is running but won't talk to the Central Controller:

Check the Address: Physically verify the rotary switch positions.
Verify Range: Ensure the IU AD is less than or equal to 64.
Power Cycle: After changing a rotary switch, you must power cycle the indoor unit for the new address to be registered by the communication PCB.