Specifications

60 Catalog WSC/WDC-4
NOTES for Following Wiring Diagram
1. Compressor motor starters are either factory mounted and wired, or shipped separate for field
mounting and wiring. If provided by others, starters must comply with McQuay specification
359AB99. All line and load side power conductors must be copper.
2. If starters are freestanding, then field wiring between the starter and the control panel is required.
Minimum wire size for 115 Vac is 12 GA for a maximum length of 50 feet. If greater than 50 feet,
refer to McQuay for recommended wire size minimum. Wire size for 24 Vac is 18 GA. All wiring
to be installed as NEC Class 1 wiring system. All 24 Vac wiring must be run in separate conduit
from 115 Vac wiring. Main power wiring between starter and motor terminal is factory-installed
when units are supplied with unit-mounted starters. Wiring of free-standing starter must be wired
in accordance with NEC and connection to compressor motor terminals must be made with
copper wire and copper lugs only.
3. For optional sensor wiring, see unit control diagram. It is recommended that dc wires be run
separately from 115 Vac wiring.
4. Customer furnished 24 or 120 Vac power for alarm relay coil can be connected between UTB1
terminals 84 power and 51 neutral of the control panel. For normally open contacts, wire
between 82 & 81. For normally closed contacts, wire between 83 & 81. The alarm is operator
programmable. The maximum rating of the alarm relay coil is 25 VA.
5. Remote on/off control of unit can be accomplished by installing a set of dry contacts between
terminals 70 and 54.
6. Evaporator and condenser flow switches are required and must be wired as shown. WDC dual
compressor units require DPDT switches. If field supplied pressure differential switches are
used then these must be installed across the vessel and not the pump.
7. Customer supplied 115 Vac, 20 amp power for optional evaporator and condenser water pump
control power and tower fans is supplied to unit control terminals (UTBI) 85 power / 86 neutral,
PE equipment ground.
8. Optional customer supplied 115 Vac, 25 VA maximum coil rated chilled water pump relay (EP 1 &
2) can be wired as shown. This option will cycle the chilled water pump in response to building
load.
9. The condenser water pump must cycle with the unit. A customer supplied 115 Vac 25 VA
maximum coil rated condenser water pump relay (CP1 & 2) is to be wired as shown.
10. Optional customer supplied 115 Vac, 25 VA maximum coil rated cooling tower fan relays (CL -
C4) can be wired as shown. This option will cycle the cooling tower fans in order to maintain unit
head pressure.
11. Auxiliary 24 Vac rated contacts in both the chilled water and condenser water pump starters must
be wired as shown.
12. For VFD, Wye-Delta, and solid state starters connected to six (6) terminal motors. The
conductors between the starter and motor carry phase current and selection shall be based on
58 percent of the motor rated load amperes (RLA). Wiring of free-standing starter must be in
accordance with the NEC and connection to the compressor motor terminals shall be made with
copper wire and copper lugs only. Main power wiring between the starter and motor terminals is
factory-installed when chillers are supplied with unit-mounted starters.
13. Optional Protocol Selectability BAS interfaces. The locations and interconnection requirements
for the various standard protocols are found in their respective installation manuals, obtainable
from the local McQuay sales office and also shipped with each unit:
Modbus IM 743-0 LonWorks IM 735-0 BACnet IM 736-0
14. The “Full Metering” or “Amps Only Metering” option will require some field wiring when free-
standing starters are used. Wiring will depend on chiller and starter type. Consult the local
McQuay sales office for information on specific selections.