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TROUBLESHOOTING GUIDE
Use the alarm display together with the chart below to check the causes of each error message.
Trouble, Alarm Codes Causes Corrective Actions
Pressure transducer alarm
PRSA
• Bad transducer
• Out of range
• Loose wire
• Wrong hook-up
• Replace the pressure transducer
• Turn off power for a few seconds, turn back on
•
Wire correctly
Outlet sensor TS1 fails
STSA
• Mechanical damage
• Connection wire loose
• Overheated
• Out of range
• Tighten the connection wires on the controller
terminal
• When brazing suction line, take out the sensor
• Install the sensor after brazing
Room sensor TS2 fails
ATSA
• Mechanical damage
• Connection wire loose
• Overheated
• Out of range
• Tighten the connection wires on the controller
terminal
• The room sensor can be replaced by surface
sensor
Low superheat
LOSH
• Superheat setting too low
• Wrong locations of TS2
• Sensors may be loose
• Uneven feeding of coil circuits
• Overcharge of refrigerant
Defective electric expansion valve
(EEV)
• Compressor stops
• Change to correct set point
• Make sure the distributor is feeding each circuit
evenly
• Insulate the sensors with foam tape
• Use correct refrigerant charge
• Check EEV wiring
• Replace defective EEV
• Check compressor
High room temperature
HITA
• Insufficient refrigeration
• Heat load too large
• Compressor fails or high pressure
cuts out
• Evaporator fans may not run
• Door open for too long
• Coil iced-up
• Check system design to select a sufficient system
• Replace failed compressor
• Fix the evaporator fans
• Keep the cold room door closed during
refrigeration
• Check possible air leak through the walls of
cold room
Low room temperature
LOTA
• Inproper low temp setpoint
• Over designed system
• Change low temp set point
• Re-select the system
Defrost termination sensor TS3
fails
CTSA
• Mechanical damage
• Loose connection wire
• Overheated
• Out of range
• Tighten the connection wires on the controller
terminal
• Let the sensor cool down to application
temperature range: –50
o
F to +103
o
F
• Replace failed sensor
Low pressure alarm
LPRA
• Refrigerant leak
• Bad transducer
• Fix leak
• Replace pressure transducer
Communication
COMA
• Loose RS-485 coonection
• Failed communication port
• Tighten the terminals
• Change a new controller board
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