Emerson Liebert MC Microchannel Outdoor Condenser 28 - 220kW User Manual

The Liebert Lee-Temp head pressure control system utilizes head pressure control valve(s), extra 

refrigerant and insulated refrigerant receiver(s) with heater pads to assist system starting and to 

maintain proper operating head pressures in outdoor ambient temperatures below the rating point of 

the Liebert MC control type. The system works by flooding the condenser coil with liquid refrigerant 

to a level that balances the system condensing requirements with the condenser coil surface available 

to reject the system heat. During the summer, the system requires the entire condenser coil surface 

for heat rejection and most of the refrigerant is stored in the receiver. In the winter, the same amount 

of heat can be rejected by only a fraction of the coil surface. As head pressure begins to fall, the control 

valve restricts the flow of liquid refrigerant existing from the condenser. This extra liquid refrigerant 

reduces the effective condenser surface area available for heat transfer. The head pressure control 

valve also bypasses hot gas into the receiver to warm the liquid and maintain liquid pressure for 

proper operation of the expansion valve. Liebert Lee-Temp kit is optional for condensers and is 

field-installed. Condenser control boards are factory-configured for Liebert Lee-Temp if ordered with 

Liebert Lee-Temp receivers. They can be field-configured if Liebert Lee-Temp system is added later.

Liebert MC condensers utilize low air resistance coil(s) and slower speed fan motors to yield the 

required heat rejection at significantly lower sound levels. EC fans are designed to yield the same 

maximum sound levels at summer design conditions to help your facility meet noise codes with 

moderate operating sound levels. 

Special match ups of premium condensers are available for applications needing to meet even lower 

governmental sound regulations. Lower sound levels are achieved by oversizing the condenser, which 

will decrease the maximum airflow and sound level produced by the condenser at design outdoor air 

temperatures. This feature requires special setup of the indoor unit. Liebert Lee-Temp may be 

required for these applications.

An optional surge protection device (SPD) can be field-wired to protect the condenser from surges that 

threaten sensitive equipment. The condenser’s electrical panel provides a terminal block to allow the 

SPD to be wired in parallel with the high-voltage power. An additional low-voltage terminal block is 

provided on condensers with Premium Control Boards to allow monitoring of the SPD alarm circuit.
The Liebert PowerSure CM

™

 surge protection device provides 50kA per mode of surge current 

protection. An illuminated green LED indicates the SPD is On and providing full protection. An 

illuminated red LED indicates that the device’s protection may have been reduced and may require 

replacement.
Both lights extinguished indicates there is no power to the condenser or the condenser disconnect is in 

the Off position.