7. LEAD/LAG OPERATION: Whenever a compressor needs to be on, the controller will turn on the compressor with the
shorter accumulated run time provided its 3 minutes minimum off time has lapsed. Otherwise the other compressor will
on first. Similarly, the compressor with the longer accumulated run time will be the first one to be cut off. This is to load
the compressors evenly over long run period. Balance loading is enabled when compressor #1 lead option is disabled.
8. AUTO MODE: In Auto mode, operating mode will be selected automatically between Heat and Cool mode, depending
on the Room Temperature and Set Temperature.
9. ERROR CODE:
Error code is displayed on the LCD panel. When system on and error code is shown, the ON/OFF LED on the LCD
panel will blink. When system off, error code is still display for thermistor error but the ON/OFF LED will be off.
E06
Compressor 1 high pressure trip (or contact open)
E07
Compressor 2 high pressure trip (or contact open), (not applicable for single compressor units)
E10
Compressor 1 low pressure trip
E11
Compressor 2 low pressure trip, (not applicable for single compressor units)
CRANKCASE HEATER
The crankcase heater is provided to hold the compressor oil reservoir at higher temperature than the coldest part in the
system.
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Power must be supplied to crankcase heater for a minimum of 12-hours prior to system start-up. If power is off for 6-
hours or more, crankcase heater must be energized for 12-hours before operating the system. Otherwise compressor
damage may result.
PUMP DOWN CONTROL
If the unit is provided with pumpdown system, then a solenoid type valve is installed in the liquid line ahead of expansion
valve to prevent flow of refrigerant into the evaporator during off cycle. The controller is wired to solenoid valve which
energize in cooling and opening the valve. Whenever the thermostat temperature is satisfied, the solenoid will close
followed compressor off after pumping the refrigerant from low side of the system until the low pressure switch open the
control circuit.
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