H21 - Indoor float switch operation abnormality.
Panasonic lists H21 as an indoor float switch operation abnormality in the self-diagnosis table for inverter air conditioners.
Applied here to Wall-Mounted Standard Inverter R32 MPU multi-split models, but Panasonic says exact code support and interpretation can vary by operating instructions.
Severity
High
Display
Displayed as H21 by the self-diagnosis function on compatible Panasonic inverter air conditioners.
Support first?
Often not
Models in range
CS-MPU9YKZ, CS-MPU12YKZ, CS-MPU18YKZ
What to do first
Start with these checks
- 1Turn the system off if the code remains active.
- 2Record the exact code and check the operating instructions for the installed model.
- 3Arrange service if the fault does not clear.
Likely causes
What usually sits behind this code
The indoor float switch is operating abnormally.
Condensate level detection is not behaving normally.
Contact support
Contact customer support if any of these apply
- !The code persists or returns quickly.
- !Water handling or indoor drainage diagnosis is needed.
- !The unit stops unexpectedly during cooling.
- - Panasonic's self-diagnosis article says to note the code and contact a qualified service technician for inspection, troubleshooting, and repairs.
- - Model-specific operating instructions may give additional information about how this protection behaves.
More ranges
More Panasonic air-conditioner ranges
Source notes
Source and scope
Source: Panasonic Cambodia HVAC
Panasonic's official self-diagnosis page lists H21 as 'Indoor float switch operation abnormality'.
Last reviewed: 2026-04-19
Panasonic says the self-diagnosis function is for identifying potential malfunctions. Repairs and complex troubleshooting should be handled by a qualified service technician.