Specifications

IMM WMC-2 Centrifugal Chillers 19
Electrical Data
Wiring, fuse and wire size must be in accordance
with the National Electric Code (NEC).
Important: The voltage to these units must be
within ±10% of nameplate voltage, and the
voltage unbalance between phases must not
exceed 2%. Since a 2% voltage unbalance will
cause a current unbalance of 6 to 10 times the
voltage unbalance per NEMA MG-1, 1998
Standard, it is most important that the unbalance
between phases be kept at a minimum.
Power Wiring
The standard power wiring connection to WMC
chillers is multi-point, i.e. a separate power
supply to each circuit’s terminal box. Single-
point connection to a terminal box, located under
the low voltage control panel, is available as an
option, in which case the individual circuit
breakers for each circuit are retained. The single
point connection is to a standard power block or
optional single unit disconnect switch.
The electrical panel (as shown to the right)
contains the circuit breaker/ disconnect (standard
on both multi-point connection and single-point
connection), a line reactor, and a radio frequency
(RF) filter. The circuit breakers provide compressor overload protection.
Proper phase sequence to the unit is not required as far as the unit operation is concerned. Correct motor
rotation is established by the chiller control system regardless of the connected phase sequence.
! DANGER
Qualified and licensed electricians must perform wiring. An electrical shock hazard exists that
can cause severe injury or death.
Table 5, WMC Electrical Connections
Standard Amp Rating
High Short Circuit Current
Rating, HSCC
Power Connection
Power Block Disconnect Power Block Disconnect
Single-point
Terminal Box
Standard Rated
Power Block
Standard Rated Molded
Case Disc. Switch
HSCC Rated
Circuit Breaker
Single-point
Each Compressor
Electric Box
Standard Rated
Circuit Breaker
Standard Rated
Circuit Breaker
Not Available
HSCC Rated
Circuit Breaker
Multi-point
Not Available
(2) Standard Rated
Circuit Breakers
Not Available
(2) HSCC Rated
Circuit Breakers
NOTES
1. Bold type combination is standard offering, all other combinations are options.
2. Circuit breakers have through-the-door disconnect switch handle.
3. When HSCC rating is included, the entire two compressor electric boxes, and single-point box if ordered, are HSCC
rated. HSCCR at 460volts is 65 kA.
General Note: The RLA for use in the following tables is obtained by the selection of a specific unit by
McQuay. When shipped, a unit will bear the specific RLA, stamped on the nameplate, for the selected
operating conditions. The tables below are for 60 Hz, 460 volts and 50 Hz, 400 volts.
Figure 14, Electrical Panel, Multi-Point
Connection
Circuit
Breaker
(3) Controller
Transformers
120V-24V
Control Power
Transformer
480V-120V
Line
Reactors
Incoming
Lugs
Power
Entry