8
IM 676
Figure 4, Typical field evaporator water piping
Flow Switch
Mount a water flow switch in either the entering or leaving water line to shut down the unit when
water flow is interrupted.
A flow switch is available from McQuay (part number 00175033-00). It is a “paddle” type
switch and adaptable to any pipe size from 3” (76mm) to 8” (203mm) nominal. Certain minimum
flow rates are required to close the switch and are listed in Table 3. Installation should be as shown
in Figure 5. Connect the normally open contacts of the flow switch in the unit control center at
terminals 5 and 6. There is also a set of normally closed contacts on the switch that can be used for
an indicator light or an alarm to indicate when a “no flow” condition exists. Freeze protect any flow
switch that is installed outdoors.
NOTE: Differential pressure switches are not recommended for outdoor installation.
Table 3, Flow switch minimum flow rates
NOMINAL PIPE SIZE
MINIMUM REQUIRED FLOW TO
INCHES (MM)
ACTIVATE SWITCH - GPM (L/S)
1 (25.4)
6.00 (0.38)
11/4 (31.8)
9.80 (0.62)
11/2 (38.1)
12.70 (0.80)
2 (50.8)
18.80 (1.20)
21/2 (63.50
24.30 (1.50)
3 (76.20
30.00 (1.90)
4 (101.6)
39.70 (2.50)
5 (127.0)
58.70 (3.70)
6 (152.4)
79.20 (5.00)
Figure 5, Flow switch installation
Water Connections
Bring water piping to the cooler from the bottom of the unit or through the side between the vertical
supports.
Flow direction
marked on switch
1" (25mm) NPT flow
switch connection
Tee
5" (127mm) pipe dia.
Min. before switch
5" (127mm) pipe dia.
Min. after switch
Protect all field piping
against freezing
Vibration
Eliminator
Vibration
Eliminator
Flow
Switch
Balancing
valve
Gate valve
Valved
pressure
gauge
Water
strainer
Gate valve
Vent
Outlet
Drain
