McQuay seasoncon ALP-067A Installation And Maintenance Data page 18

Flow Switch for Chilled Water Applications
A WATER FLOW SWITCH MUST BE MOUNTED in either the entering or leav-
ing water line to insure that there will be adequate water flow and
cooling load to the evaporator before the unit can start.
safeguard against slugging the compressors on start up.
serves to shut down the unit in the event that water flow is inter-
rupted to guard against evaporator freeze up.
A flow switch is available from McQuay under ordering number 860-
size from 1" to 6" nominal.
to close the switch and are listed in Table 11.
be as shown in Figure 13.
TABLE 11
FLOW SWITCH MINIMUM FLOW RATES
NOMINAL
PIPE SIZE
(INCHES)
1
1 l/4
1 l/2
2
2 l/2
3
4
5
6
Electrical connections in the unit control center should be made at
terminals 11 and 12.
should be wired between these two terminals.
normally closed contacts on the switch that could be used for an in-
dicator light or an alarm to indicate when a "no flow" condition
exists.
Evaporator Fan Interlock for Air Handler Coil Installations
It is important to interlock the air handler evaporator fan with the
condensing unit control center to insure that there will be a cooling
load on the evaporator before the unit can start, to prevent com-
pressor slugging.
is available in the unit control center for this purpose.
terminal numbers are shown in Figure 12.
page 18
It is a "paddle"
MINIMUM REQUIRED
FLOW TO ACTIVATE
SWITCH (GPM)
6.00
9.80
12.70
18.80
24.30
30.00
39.70
58.70
79,20
The normally open contacts of the flow switch
A pair of terminals for each refrigerant circuit
type switch and adaptable to any pipe
Certain minimum flow rates are required
FIGURE 13
AFTER SWiTCH
This will
It also
Installation should
FLOW DIRECTION
MARKED ON SWITCH
1.00 NPT FLOW SWITCH
CONNECTION
BEFORE SWITCH
There is also a set of
These