IM 950-1 / Page 3 of 38
Fault code
Description
Cause for the fault
CE
Communication Error
1. Cable not plugged in properly on either LUI or relay board.
2. Defective cable.
Sh
Missing Shunt
The user configurable shunt for System Select, Control Select Off Fan Cycle, and/or Hydronic Valve is
missing or not placed properly.
E1
Problem with IAS
Indoor Air Sensor missing or short.
E2
Problem with ICS
Indoor Coil Sensor missing or short.
E3
Problem with OCS
Outdoor Coil Sensor missing or short.
E4
Problem with OAS
Outdoor Air Sensor missing or short.
E5
Problem with HFLO Sensor HFLO Sensor missing or short on AP7809. Check for installation / connection of HFLO sensor. Should
be on coil return line.
Protection
Description
Cause for the fault
code
CF
Coil Freeze Protection
Indoor coil temperature has been below 32ºF for 5 minutes.
Protection feature and the displayed code are dismissed when indoor coil temperature rises above 49ºF.
Rf
Room Freeze Protection
Indoor air temperature has dropped below 41ºF. Protection feature and the displayed code are
dismissed when indoor room temperature rises at and above 50ºF.
hI
High Room Temperature
Indoor air temperature is 5 degrees above maximum setpoint limit. Protection feature and the displayed
code are dismissed when indoor coil temperature rises above 50ºF.
Lo
Low Room Temperature
Indoor air temperature is 5 degrees below minimum setpoint limit.
LA
Low Ambient Lockout
Outdoor air temperature is below 35ºF.
Fault and Protection Codes for Applied PTAC/PTHP Control Board
Fault code
Description
Cause for the fault
LC
Control Lockout –
Displays for 5 seconds when any button is pushed when in the "lockout mode".
nL
Control Lockout –
Displays for 5 seconds to confirm normal mode of operation when control lockout turned off.
Normal Control
CL
Damper Closed
Control setup indicator damper is in "closed" mode.
AU
Auto Damper
Control setup indicator damper is in "automatic" mode.
AU
Auto HP/E
Control setup indicator heat pump electric is in automatic changeover mode (HP/E).
bY
HP/E Bypass
Control setup indicator, electric heat is bypassed when OCS > 40˚.
CF
Coil Freeze Protection
Indoor coil is ≤ 32˚ for at least 5 minutes. Compressor and outdoor fan stop and indoor fan continues
to run for active defrost.
rF
Room Freeze Protection
Room temperature < 41˚. Damper closes (Premium board) and unit goes into heat mode.
Lo
Coil freeze protection
Room temperature is 5˚ below set point.
Hi
Temperature Limiting
Room temperature is 5˚ above set point.
LA
Low Ambient Lockout
Unit is in cooling mode and outdoor air < 35˚. Compressor will cut out.
E1
Indoor Air Sensor
Indoor Air Thermister Failure.
E2
Indoor Coil Sensor
Indoor Coil Thermister Failure.
E3
Outdoor Coil Sensor
Outdoor Coil Thermister Failure.
E4
Outdoor Air Sensor
Outdoor Air Thermister Failure.
E5
Problem with HFLO Sensor HFLO Sensor missing or short on AP7809. Check for installation / connection of HFLO sensor. Should
be on coil return line.
Solid State Digital Controls – Local User Interface Display Codes
