Daikin VRV IV RXTQ-TA / RXTQ-TB error code UC
Centralized controller address duplication, warning
Which models this applies to. System
Quick answer
On Daikin VRV IV RXTQ-TA / RXTQ-TB, UC is a fault. It means centralized controller address duplication, warning. A first thing to check: Two centralized controllers assigned the same address.
- Applies to
- Daikin VRV IV RXTQ-TA / RXTQ-TB
- Daikin VRV IV RXTQ heat pump codes · Heat Pump
- Type of code
- Fault
- Urgency: Worth keeping an eye on
- First safe check
- List the address of every centralized controller on the system and look for a duplicate, which is the whole of the diagnosis.
What UC means on this model
Two centralized controllers have been given the same address, so the system runs but one of them cannot be individually monitored or controlled. The operation lamp stays lit. Listing every controller address and comparing them is the whole of the diagnosis.
Symptoms you will notice
- System shows UC with the operation lamp lit
- One controller cannot be reached or shows the same units as another controller
- The fault appeared after a controller was added or re-addressed
Common causes
The code tells you what the control detected, not which part failed. These are the causes we see most often, roughly in order of likelihood:
- Two centralized controllers assigned the same address
- A controller replaced without re-addressing it
- An addressing error during commissioning
- A controller restored to a default address that matches an existing one
What you can safely check
These are homeowner-level checks. None of them need you to open a live electrical compartment or work on gas.
- List the address of every centralized controller on the system and look for a duplicate, which is the whole of the diagnosis.
- Check whether a controller was recently replaced or added, since a replacement defaults can easily collide with an existing address.
Do not do these
- ×Do not leave the duplication in place. The system runs, but one controller is effectively dead and will not report or control its zones.
- ×Do not change the address of a controller you have not identified, since the duplicate is only findable by comparing all of them.
When to call a technician
No call needed yet, but write it down
Note the date and the exact code, and watch whether it comes back. If it turns into a repeat fault or starts affecting performance, that is when it becomes worth a technician.
- The refrigerant circuit is sealed and legally requires licensed handling. Opening it without certification releases refrigerant and can put the whole system in violation of regulation, so a low-pressure or high-pressure fault on this equipment is a call-out, not a weekend job.
- If the appliance has stopped mid-cycle, is making a noise you have not heard before, or smells burnt, stop reading here and call. Those are symptoms of something the fault code does not describe well enough.
A commissioning technician job. Addressing is done with the manufacturer tools.
What it costs to fix
Parts
None expected.
Labor
One to two hours to re-address the duplicated controller.
DIY or technician
A commissioning technician job. Addressing is done with the manufacturer tools.
Typical US part and labor ranges, 2026. They vary by region, model and contractor, so treat them as a planning figure, not a quote.
Scope of this code
- Code table
- Daikin VRV IV RXTQ heat pump codes
- Models in scope
- Daikin VRV IV RXTQ-TA / RXTQ-TB
- Checked
- Confirm on your own unit
- Find the model number on the data plate, then check this code in the service manual for that model. Manufacturers revise code tables between model years, and a revised board can renumber a fault.