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 
49 
(2) The following situations are not operation failures.
Problem 
Time of occurrence 
Cause 
Mist comes from the air 
conditioner.   
During operation. 
If the unit is running under high humidity, the 
wet air in the room will be quickly cooled 
down.   
The air conditioner generates 
some noise.   
The air conditioner is buzzing at the beginning 
of operation.   
Thermostat will be buzzing when it starts 
working. The noise will become weak 1min 
later.     
Dust comes from the air 
conditioner.   
When the unit is turned on, it purrs. 
When the system is just started, the 
refrigerant is not stable. About 30s later, the 
purr of the unit becomes low.   
There is hissing sound when the unit is started 
or stopped and a slight hissing sound during 
and after operation.   
It’s the sound of gaseous refrigerant that stops 
flowing and the sound of drainage system.   
There is a sound of crunching during and after 
operation.   
Because of temperature change, front panel 
and other components may be swelled up and 
cause abrasion sound.   
There is a hissing sound when the unit is 
turned on or suddenly stopped during 
operation or after defrosting.   
Because refrigerant suddenly stops flowing or 
changes the flow direction.   
The unit starts operation after being unused 
for a long time.   
Dust inside the units come out together with 
the air.   
The air conditioner generates 
some smell.   
During operation. 
The room smell or the smell of cigarette 
comes out through the units.   
NOTICE:
Check the above items and adopt the corresponding corrective measures. If the air conditioner continues to 
function poorly, please stop the air conditioner immediately and contact a MRCOOL authorized local service
center. 
Ask our professional service staff to check and repair the unit. 










