Use and Care Manual
Table Of Contents
- Foreword
 - Safety Notice
 - CONTENTS
 - Safety Notice on Maintenance
 - Safety Notice on Operation
 - 1 Product Introduction
 - NOTE: 1 Ton =12000Btu/h = 3.517kW 1.2 Electrical Parameters
 - 2 Control
 - 3 Troubleshooting
- 3.1 Wiring Diagrams
 - 3.2 PCB Layout
 - 3.3 Error Code
 - 3.4 Troubleshooting
- 3.4.1 “E1” Compressor High Pressure Protection
 - 3.4.2 “E3” Compressor Low-pressure Protection, Refrigerant Shortage Protection, Refrigerant Recovery Mode
 - 3.4.3 “E4” Compressor Air Discharge High-temperature Protection
 - 3.4.4 “F2” Condenser Temperature Sensor Error
 - 3.4.5 “F3” Outdoor Ambient Temperature Sensor Error
 - 3.4.6 “F4” Discharge Temperature Sensor Error
 - 3.4.7 “F6” ODU Tube Temperature Sensor Error
 - 3.4.8“EE” ODU Memory Chip Error
 - 3.4.9 “H4” Overload
 - 3.4.10 “H5” IPM Protection
 - 3.4.11 “H6” DC Fan Error
 - 3.4.12 “H7” Driver Out-of-Step Protection
 - 3.4.13 “HC” PFC Protection
 - 3.4.14 “Lc” Startup Failure
 - 3.4.15 “P0” Driver Reset Protection
 - 3.4.16 “P5” Over-Current Protection
 - 3.4.17 “P6” Master Control and Driver Communication Error
 - 3.4.18 “P7” Driver Module Sensor Error
 - 3.4.19 “P8” Driver Module High Temperature Protection
 - 3.4.20 “PA” AC Current Protection
 - 3.4.21 “Pc” Driver Current Error
 - 3.4.22 “PL” Bus Low-Voltage Protection
 - 3.4.23 “PH” Bus High-Voltage Protection
 - 3.4.24 “PU” Charge Loop Error
 - 3.4.25 “ee” Drive Memory Chip Error
 
 - 3.5 Failures Not Caused by Errors
 
 - 4 Maintenance
 - Appendices
 - 1 Resistance/Temperature Lists of Temperature Sensors
- 1.1 Voltage List of 15 KΩ Temperature Sensors (including ODU temperature sensors)
 - 1.2 Voltage List of 20 KΩ Pipeline Temperature Sensors (including temperature sensors for defroster, IDU and ODU pipes)
 - 1.3 Voltage List of 50 KΩ Discharge Temperature Sensors (including discharge air temperature sensor)
 
 - 2 Temperature/Pressure List of Refrigerant
 - 3 Operation Tools
 
MRCOOL DC INVERTER COOLING ONLY CONDENSING UNIT 
56 
Refer to the following table for the resistance between any two terminals: 
Compressor model 
UV Winding resistance 
VW Winding resistance 
WU Winding resistance 
QXAS-D32zX090FA 
1.02±7%Ω 
1.02±7%Ω 
1.02±7%Ω 
QXAS-F428zX450L 
0.54±7%Ω 
0.54±7%Ω 
0.54±7%Ω 
Measure the earth resistance of each wiring terminal. The resistance should be above 10 megohm. If not, we 
can judge that the compressor is faulted inside.   
Step 3: 
Check  whether  the  IPM  module  is  normal.  Please  refer  to  the  IPM  checking  method  in  the  section  of 
troubleshooting. 
4.4.2.2 Replacement of compressor 
Step 1: Preparation 
(1) Prepare the components for replacement
When carrying the old and new compressors, do not place the compressors horizontally or upside down. The 
angle of inclination should be within ±30°. Make sure the lubricant inside the compressors will not flow from the oil 
balance mouth. The suction and exhaust openings of the compressors must be sealed. If a rubber seal is missing, 
user adhesive tape to seal the opening. This is to prevent the compressor oil from contacting the air.   
Make  sure  the  rubber  seals 
of  the  suction  and  exhaust 
openings of  the  compressor 
are in good condition. 










