16. Press the ENT button.
17. In the System Control configuration parameter, use the UP or DOWN arrow button to select 1.
18. Press the ENT button. The display reads 888 if the command is accepted.
19. Press the ESC button to display C24. All fans should return to a normal speed based on the pressure input and
the state of indoor unit’s compressor.
11.5 Replacing the Premium Efficiency Control Board
Use these steps to replace the Premium Efficiency Control Board in the condenser.
WARNING! Arc flash and electric shock hazard. Open all local and remote electric power supply disconnect
switches, verify with a voltmeter that power is Off and wear appropriate, OSHA-approved personal protective
equipment (PPE) per NFPA 70E before working within the electric control enclosure. Failure to comply can
cause serious injury or death. Customer must provide earth ground to unit, per NEC, CEC and local codes, as
applicable. Before proceeding with installation, read all instructions, verify that all the parts are included and
check the nameplate to be sure the voltage matches available utility power. The Vertiv™ Liebert® iCOM™
controller does not isolate power from the unit, even in the Unit Off mode. Some internal components require
and receive power even during the Unit Off mode of the Liebert® iCOM™ controller. The only way to ensure
that there is NO voltage inside the unit is to install and open a remote disconnect switch. Refer to unit
electrical schematic. Follow all local codes.
11.5.1 Preparing to Replace the Board
1. Verify that the following jumpers are installed on the new board (see Figure 11.1 on the facing page):
• Jumper at J4 and J6 on Pins 2 and 3.
• Jumper on J2.
• Jumper on J5 on Pins 1 and 2.
2. Locate the latest revision of the HMI parameters label, 303847P1, included with the new control board.
NOTE: In Figure 11.1 on the facing page, J6 is the CANbus termination jumper. J4 is the RS485 service termination
jumper. If the condenser is the last device in the CANbus communication line, the jumper must be placed between Pins
1 and 2 of J6. If the condenser is not the last device in the CANbus communication line, the jumpers on J6 must be
placed on Pins 2 and 3. If the jumper is not in the correct positions, CANbus communication errors may occur. The
jumper on J4 will always be placed between Pins 1 and 2.
NOTE: In Figure 11.1 on the facing page, a jumper must be present at J2. If a jumper is not present, the control board
will not boot properly during power start-up.
62 Proprietary and Confidential ©2024 Vertiv Group Corp. 11 Maintenance
Vertiv™ Liebert® MCV Installer/User Guide
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