Install Instructions
6
d. Based upon the mode of operation (“Flow” or “No-
Flow”) required, complete the appropriate steps to 
connect wires to flow switch. Use a Phillip’s head 
screwdriver to loosen and tighten switch terminal 
screws when attaching wires.
For “Flow” Mode of Operation (Fig. 1)
If the flow switch will be used to actuate a signal, 
alarm or other device when 
flow
occurs, connect 
the wire from that device to the “N.O.” contact.
Connect the “Hot” power supply wire to “C” terminal.
For “No Flow” Mode of Operation (Fig. 2)
If the flow switch will be used to actuate a signal, 
alarm or other device when 
no flow
occurs, connect 
the wire from that device to the “N.C.” contact.
Connect the “Hot” power supply wire to “C” terminal.
Flow
Opens
Circuit
Normally
closed
3
Common
1
Flow
Closes
Circuit
2
(
(
Normally
open
(
(
Common
(
(
FS4-3
LINE
LOAD
Fig. 1
HOT
31
2
FS4-3
LINE
LOAD
Fig. 2
HOT
31
2
C. N.O.
FLOW
N.C. C. N.O.
NO FLOW
N.C.
c. Determine which switch action is required for the 
flow switch.
• “Flow” means that the switch will close circuit 
C.-N.O. and open circuit C.-N.C. when flow rate 
is increased above setpoint of flow switch.
• “No Flow” means that the switch will open circuit 
C.-N.O. and close circuit C.-N.C. when flow rate 
is decreased below setpoint of flow switch.








