Daikin VRV IV RXTQ-TA / RXTQ-TB error code UH
System address undefined
Which models this applies to. System
Quick answer
On Daikin VRV IV RXTQ-TA / RXTQ-TB, UH is a fault. It means system address undefined. A first thing to check: The system address has been cleared or lost.
- Applies to
- Daikin VRV IV RXTQ-TA / RXTQ-TB
- Daikin VRV IV RXTQ heat pump codes · Heat Pump
- Type of code
- Fault
- Urgency: Needs attention soon
- First safe check
- Check whether a board or the outdoor unit has been replaced recently, because that is the common way a running system loses its address.
What UH means on this model
A system that was running has lost its address, so the outdoor and indoor units no longer agree which system they belong to. It usually follows a power interruption, an incomplete settings change or a board replacement, and the system cannot distribute refrigerant because it does not know what it is connected to.
Symptoms you will notice
- System shows UH and the system stops
- The system was working and stopped after a power interruption
- Field settings were changed recently
- A board or an outdoor unit was replaced
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:
- The system address has been cleared or lost
- A power interruption during a configuration change
- A field settings change that did not complete
- A replaced outdoor unit or main board that was not set up with the existing system address
- A memory or backup failure in the system configuration
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.
- Check whether a board or the outdoor unit has been replaced recently, because that is the common way a running system loses its address.
- Check whether a power interruption or a field settings change happened before the fault appeared.
Do not do these
- ×Do not re-address the system without recording the existing addresses, because losing them makes the system harder to put back.
- ×Do not assume the outdoor unit has failed. UH is an addressing code and a board replacement will not fix it.
When to call a technician
Book a technician, do not keep resetting it
This fault will not clear on its own. Every power cycle gives the control one more failed attempt, and repeated attempts are what turn a cheap part replacement into a seized or contaminated system.
- 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.
What it costs to fix
Parts
None expected if the address can be restored.
Labor
Two to five hours to redefine the system and verify it.
DIY or technician
A commissioning technician job.
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.