Specifications

6 Centrifugal Chillers IMM WMC-2
The piping should include thermometers at the inlet and outlet connections and air vents at the high points.
The water heads can be interchanged (end for end) so that the water connections can be made at either end of the
unit. If this is done, use new head gaskets and relocate the control sensors.
In cases where the water pump noise can be objectionable, vibration isolation sections are recommended at both
the inlet and outlet of the pump. In most cases, it will not be necessary to provide vibration eliminator sections
in the condenser inlet and outlet water lines. But they can be required where noise and vibration are critical.
Important Notes on Welding
If welding is to be performed on the mechanical or flange connections:
1. Remove the solid-state temperature sensor, thermostat bulbs and optional nozzle mounted flow switches (if so
equipped) from the wells to prevent damage to those components.
2. Properly ground the unit or severe damage to the MicroTech II® unit controller can occur.
Note: ASME certification will be revoked if welding is performed on a vessel shell or tube sheet.
Water pressure gauge connection taps and gauges must be provided in the field piping at the inlet and outlet
connections of both vessels for measuring the water pressure drop. The pressure drops and flow rates for the
various evaporators and condensers are job specific and the original job documentation can be consulted for this
information. Refer to the nameplate on the vessel shell for identification.
Connections
Be sure that water inlet and outlet connections match certified drawings and stenciled nozzle markings. The
condenser is connected with the coolest water entering at the bottom connection to maximize subcooling. The
evaporator outlet is on the right side of the head, regardless of which end the connections are on.
! CAUTION
When common piping is used for both building heating and cooling modes, care must be taken to
provide that water flowing through the evaporator cannot exceed 110°F. Water this hot can cause
the relief valve to discharge refrigerant or damage controls.
Piping must be supported to eliminate weight and strain on the fittings and connections. Chilled water piping
must be adequately insulated. A cleanable 20-mesh water strainer must be installed in both water inlet lines.
Sufficient shutoff valves must be installed to permit draining the water from the evaporator or condenser without
draining the complete system.
Flow Switch
Note: Chiller units must have flow switches for the evaporator and
condenser. McQuay furnishes factory-installed and wired, thermal-
type flow switches as standard equipment on WMC chillers. Field-
installed and wired Delta-P switches can be used instead.
They prevent the unit from starting without sufficient water flow
through the vessels. They also serve to shut down the unit in the
event that water flow is interrupted to guard against evaporator
freeze-up or excessive discharge pressure.
Additionally, for a higher margin of protection, normally open
auxiliary contacts in the pump starters can be wired in series with
the flow switches as shown in the Field Wiring Diagram on page 23.
Figure 2, Unit-Mounted Flow Switch