Miniature Adjustable Current Switches
Installation and Operation
#NSA-A/MCS-A, NSA-A/MSCS-A
– 11/14/2019
Specifications subject to change without notice.
Catalog No. 11-808-762-01
Page
4
of
5
For applications in which the normal operating current is greater than 150 Amps or for conductor diameters larger than
0.530” (1.35 cm) in diameter, an external 5 Amp Current Transformer must be used as shown in Figure 4 below.
Remember that the secondary of the 5A CT must be shorted together before the power may be turned onto the monitored
device.
Figure 4
Wiring Instructions
Carriers recommends the use of a two conductor 16 to 22 AWG shielded cable or twisted pair copper wire only for all
current switch applications. A maximum wire length of less than 30 meters (98.4 feet) should be used between the NSA-
A/MCS-A and NSA-A/MSCS-A current switches and the Building Management System or controller.
NOTE
When using a shielded cable, be sure to connect only (1) end of the shield to ground at the controller. Connecting
both ends of the shield to ground may cause a ground loop.
When removing the shield from the sensor end, make sure to properly trim the shield so as to prevent any chance of
shorting. The current switch output terminals represent a solid-state switch for controlling both AC and DC loads and is not
polarity sensitive. The recommended torque to be used on the terminal block connections is 0.67 Nm or 5.93 in-lbs. The
aperture (hole) size of the current switch is 0.53” (1.35 cm) and will accept a 1 AWG maximum wire diameter.
See Figure 5 and Figure 6 for two different current switch applications using your Building Management System (DDC/PLC
Controller). Figure 5 shows the use of the Adjustable Current Switch as a Digital Input to your DDC Controller, whereas
Figure 6 shows you how to use the Adjustable Current Switch in conjunction with your building management system to
monitor belt loss on a motor.
Digital Circuit
Analog Circuit
Figure 5
Figure 6
