Vertiv Liebert MCM080 - 4.2 Low-voltage Control Wiring-CANbus Communication and Interlock Connections

• Delta with grounded center tap
4.2 Low-voltage Control Wiring—CANbus Communication andInterlock
Connections
NOTICE
Risk of control malfunction. Can cause improper unit operation.
Verify that all low-voltage electrical wiring has been performed per the schematic diagram provided and
that all low-voltage wiring connections are tight.
CANbus communication and interlock wiring are required between the indoor and the outdoor units.
CANbus cables are supplied by others to connect the indoor unit to the outdoor condenser. No special
considerations are required when the total external cable connection between the indoor unit and
outdoor unit is less than 450 ft. (137m). A CANbus isolator is required for total external cable connections
longer than 450ft.(137m) but less than 800 ft. (243m).
CANbus Cable Requirements
• conductors 22-18AWG stranded tinned copper
• twisted pair (minimum four twists per foot)
• braided shield or foil shield with drain wire
• shield must always be wired to ground at the indoor unit
• low capacitance (15pF/ft or less)
• UL-approved temperature rated to 75°C
• UL-approved voltage rated to 300V
• UV-resistant and moisture-resistant if not run in conduit
• plenum-rated NEC Type CMP, if required by national or local codes
• Examples include: Belden 89207 (plenum-rated), or Alpha Wire 6454 Category 5, 5e or higher
Interlock wiring is field-supplied wiring between Terminals 70 and 71 for single-circuit models and
Terminal 230 also for dual-circuit models. Total interlock wire length must be less than 1000ft. (305m).
Field-Supplied Interlock Wire
• 18AWG or greater
• rated 600V
Notes on Electrical Connections
• Do not run CANbus cable and interlock wires in same conduit, racewary or chase as high-
voltage wiring.
• No special considerations are required when the total external cable connection between the
indoor unit and outdoor unit(s) is less than 450 ft. (137m). A CANbus isolator is required for
total external cable connections greater than 450 ft. (137m) but less than 800 ft. (243m).
• All wiring must be sized and selected for insulation case per NEC and other applicable codes.
• Do not bend cables to less than four times the diameter of the cable.
• Do not deform cables when securing in bundles or when hanging them.
Vertiv | Liebert® MC™ Installer/User Guide | 43