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2WAY VRF SYSTEM
Trouble Diagnosis
3. 2WAY Alarm Codes
H21, H31 Alarm (U-72ME2U9 / U-96ME2U9 / U-120ME2U9 / U-144ME2U9)
Alarm code
Alarm meaning
Alarm conditions
temperature or other trouble) from the HIC.
The HIC judges the current and temperature, and outputs the trouble signal. In general this
indicates trouble with the HIC itself.
Probable cause
Check
H21, H31
H21 : HIC for 2nd compressor has failure. Overcurrent or overheat of HIC.
H31 : HIC for 1st compressor has failure. Overcurrent or overheat of HIC.
This alarm occurs when the microcomputer identifies a trouble signal (indicating abnormal HIC
Overcurrent in HIC circuit, and the resultant abnormal heating, caused by HIC failure
Check the power wiring and connector wiring. If the wiring and connectors are normal, use a
tester to measure the resistance between the compressor HIC power (DC+) and ground (DC–).
If there is a short-circuit, there is an HIC malfunction.
Correction
Example
Notes
If an HIC failure is found, replace the PCB.
—
Turn OFF the power, and check the continuity of DC+ and DC– on the HIC PCB.
L04 Alarm
Alarm code
Alarm meaning
Alarm conditions
that unit 5 times or more within 3 minutes.
Probable cause
Check
Correction
Example
Notes
L04
Duplicate system address setting on outdoor units.
Communication by inter-unit control wiring was received that contained the same address as
Incorrect outdoor system address settings
Check the system address settings again.
Correct the system address settings.
—
Recovery from this alarm occurs automatically (when communication that contains the same
address as that unit is not received for 3 minutes after detection).
DC-
(N)
HIC PCB for Type 72,120 and 144
(A747843)
HIC PCB for Type 96
(A747846)
DC+
(P)
DC-
(N)
DC+
(P)
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