Carrier NSA-A/ACS2 Guide

Adjustable Current Switches
Installation and Operation
#NSA-A/ACS2, NSA-A/ASCS2, NSA-A/ASCS2-L –11/14/2019
Specifications subject to change without notice.
Catalog No. 11-808-743-01 Page 1of 7
Overview
The Adjustable Current Switches are designed for use in any AC current
monitoring application in which you are looking to monitor a particular piece of
equipment for equipment failure, preventative maintenance, status, and
electrical load status. The current switches should be installed on the line side
of the power to the electrical equipment. The current switches are available in
both solid and split-core versions which also includes a Patented 35 mm Din
Rail mounting foot for easy installation in panel mount applications. The solid-
core versions are a great choice for new installations or OEM applications in
which cost sensitivity, lower trip points and environmental issues may be of
concern. The split-core version of the current switches work great in retro t
applications and for use on service technicians’ vehicles since one part will
work in most applications and can be easily installed without disconnecting any
wires. The adjustable current switches can be used to determine the run time of
your equipment as well as basic load trending applications where you want to
know when how long your piece of equipment runs when logging the contact closures on your building management
system or PLC.
Applications: Overload Conditions, Underload Conditions, Normal Operating Conditions, Broken Belts, Belt Slippage,
Locked Rotors, Equipment Failure, Fans, Pumps, Compressors, Motors, Ovens, Industrial Equipment, Lighting Status and
Usage, Electrical Load Status, Local Alarms (Strobes and Audible Alarms), Preventative Maintenance Scheduling
Part Numbers
NSA-A/ACS2 NSA-A/ASCS2 NSA-A/ASCS2-L
Specifications
Monitored Current Type:
AC Current
Maximum AC Voltage:
600 VAC
Operating Frequency Range:
40 to 1 kHz
Core Style:
NSA-A/ACS2: Solid | NSA-A/ASCS2: Split | NSA-A/ASCS2-L: Split
Sensor Power:
Induced from the Monitored Conductor
Amperage Range:
0 to 250A
Isolation Voltage:
2200 VAC
Trip Point Style | Trip Point:
Adjustable
NSA-A/ACS2: 0.5 to 220A | NSA-A/ASCS2: 1.5 to 220A
NSA-A/ASCS2-L: 0.6 to 180A
Hysteresis:
10% of trip point, typical
Contact Type:
Normally Open (N/O)
“Status” Contact Rating:
0.2A @ 200 VAC/VDC
“Status” Contact “On” Resistance | “O” Resistance:
< 10 Ohms (tripped) | > 1 Meg Ohms (Open)
Response Time:
See Response Time Table
Status LED Indication -:
Red LED (Current above Trip Point)
Blue LED (Current Below Trip Point)
Aperture Size:
0.75” (19.05 mm)
Din Rail Size:
35 mm (U.S. Patent No. 7,416,421)
Operating Temperature Range:
5 to 104ºF (-15 to 40ºC)
Operating Humidity Range:
0 to 95%, non-condensing
Recommended Storage Temperature | RH Range:
41 to 95°F (5 to 35°C) | 40% to 85% RH, non-condensing
Enclosure Material | Flammability Rating:
PC/ABS (Polycarbonate/ABS Blend) | UL94-V0
Wiring Connections:
2 Position, Screw Terminal Block (Not Polarity Sensitive)
Wire Size:
16 to 22 AWG (1.31 mm2to 0.33 mm2) Copper Wires only

Adjustable Current Switches
Installation and Operation
#NSA-A/ACS2, NSA-A/ASCS2, NSA-A/ASCS2-L –11/14/2019
Specifications subject to change without notice.
Catalog No. 11-808-743-01 Page 2of 7
Terminal Block Torque Rating:
4.43 to 5.31 in-lbs. (0.5 to 0.6 Nm)
Minimum Mounting Distance:
1” (2.6 cm minimum) between current switch (Relays, Contactors,
Transformers)
Agency Approvals:
UL/CUL US Listed (UL 508) Ind. Control Equipment (File # E309723), CE,
RoHS2, WEEE
Product Weight:
NSA-A/ACS2: 0.216 lbs. (0.097 kg) | NSA-A/ASCS2: 0.270 lbs. (0.123 kg)
NSA-A/ASCS2-L: 0.280 lbs. (0.127 kg)
Product Dimensions (L x W x H):
Solid Core: 2.760” (70.11 mm) x 3.343” (84.92 mm) x 1.050” (26.67 mm)
Split Core: 2.780” (70.51 mm) x 3.238” (82.25 mm) x 1.120” (28.45 mm)
Response Time
Model #
0.50 Amps
0.60 Amps
0.75 Amps
1.0 Amps
1.5 Amps
10 Amps
20 Ampls
NSA-A/ACS2
221 mS
-
144 mS
109 mS
-
63 mS
59 mS
NSA-A/ASCS2
-
-
-
-
248 mS
68 mS
65 mS
NSA-A/ASCS2-L
-
400 mS
270 mS
183 mS
-
62 mS
60 mS
-: unit was not tested (below minimum trip point or for that range)
Dimensional Drawing
Solid Core
Continued on next page

Adjustable Current Switches
Installation and Operation
#NSA-A/ACS2, NSA-A/ASCS2, NSA-A/ASCS2-L –11/14/2019
Specifications subject to change without notice.
Catalog No. 11-808-743-01 Page 3of 7
Split Core
Front View
Right View
Bottom View
Figure 1
Precautions
This product is not intended to be used for Life or Safety applications.
This product is not intended for use in any hazardous or classified locations.
The NSA-A/ACS2 and NSA-A/ASCS2 Series Current Switches must be used on Insulated Conductors only.
High Voltage
Disconnect and lock out all power sources before installation as severe injury or death may result from electrical
shock due to contact with high voltage wires.
Never rely on the Red LED to determine whether power is present at the current switch. At very low monitored
input currents the Red LED may not light to indicate the current is above the trip point.
Installation
Ensure all installations are in compliance with all national and local electrical codes. Only qualified individuals that are
familiar with codes, standards, and proper safety procedures for high-voltage installations should attempt installation. The
current switches will not require external power because the power for the current switch is induced from the conductor
being monitored. The current switch may be mounted in any position using the two #8 x 3/4” Tek screws and the mounting
holes in the base, or snapped directly on to the 35mm DIN rail (Figure 3). Leave a minimum distance of 1” (3 cm) between
the current switch and any other magnetic devices such as contactors and transformers.

Adjustable Current Switches
Installation and Operation
#NSA-A/ACS2, NSA-A/ASCS2, NSA-A/ASCS2-L –11/14/2019
Specifications subject to change without notice.
Catalog No. 11-808-743-01 Page 4of 7
Latch Operation
Press down on the side tab and swing the top of the unit up to open the split core current switch as shown in Figure 2.
Press down firmly on the cover to close the current switch. An audible “click” will be heard as the tab slides over the
tongue on the base.
CAUTION Mating surfaces of the magnetic core are exposed when the sensor is open. Electrical contact grease, present
on the cores to prevent corrosion, can capture grit and dirt if care is not exercised. Operation can be impaired if anything
prevents good contact between pole pieces. Visually check the mating parts of the core before closing the current sensor.
Figure 2
LED
The Red LED will indicate whether the current is above (LED On) or below (LED Off) the fixed trip point. At very low
monitored input currents the Red LED may not light to indicate the current is above the trip point.
Din Rail Installation
Figure 3

Adjustable Current Switches
Installation and Operation
#NSA-A/ACS2, NSA-A/ASCS2, NSA-A/ASCS2-L –11/14/2019
Specifications subject to change without notice.
Catalog No. 11-808-743-01 Page 5of 7
Wires Through Sensors
Figure 4
APPLICATION NOTES
The conductor being monitored may be looped through the sensor multiple times. The loops increase the current
measured by the current switch. Each time the conductor passes through the current switch window equals one loop
(Figure 4). To determine the proper number of loops required, take the rated Fixed Trip Point of the current switch and
divide it by the Operating Current of the Monitored Device, add one (1), then round up to the nearest whole number.
Example: When using the NSA-A/ACS2, a small fan operating at 0.1A should be wrapped through the sensor four times to
give you a total operating current of 0.4 Amps flowing through the NSA-A/ACS2. Formula Example: (0.25A/0.1A) = 2.5 + 1
= 3.5, which rounded up equals 4 loops.
Wiring Instructions
Carrier 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 current
switch 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 to prevent any chance of shorting. The
current switch output terminals represent a solid-state switch for controlling both AC and DC loads and are not polarity
sensitive. Tighten the screws at the terminal block connections to the recommended torque of 0.5 to 0.6 Nm (4.43 to 5.31
in-lbs). The aperture (hole) size of the current switch is 0.75” (1.90 cm).

Adjustable Current Switches
Installation and Operation
#NSA-A/ACS2, NSA-A/ASCS2, NSA-A/ASCS2-L –11/14/2019
Specifications subject to change without notice.
Catalog No. 11-808-743-01 Page 6of 7
Digital Circuit
Figure 5
Motor/Fan Control
Figure 6

Adjustable Current Switches
Installation and Operation
#NSA-A/ACS2, NSA-A/ASCS2, NSA-A/ASCS2-L –11/14/2019
Specifications subject to change without notice.
Catalog No. 11-808-743-01 Page 7of 7
Application Examples
See Figure 5 and Figure 6 for two different current switch applications. Figure 5 shows the use of the Go/No Go Current
Switch as a Digital Input to your BAS/PLC Controller. Figure 6 shows a Go/No/Go Current Switch in conjunction with a
Contactor to control an exhaust fan.
NOTE The Go/No Go Current switches are only rated at 0.2A @ 200 VAC/VDC and must use an additional Contactor if
controlling motor/fans.
Calibration of Adjustable Trip Point
The adjustable current switch has an operating range of 0-250 Amps, Do not exceed! The current switch has an
adjustable trip point range of 0.50 - 220 Amps, 1.50 - 220 Amps, or 0.60 - 180 Amps depending on the model. See the
Specifications table to determine the adjustable trip point range per model number. The adjustable current switch comes
with its fifteen-turn adjustment potentiometer set to the maximum trip point position. The adjustable current switch can
monitor Underload, Normal Load, and Overload conditions, depending on how it’s set. The procedure below is for the
Normal load condition for part numbers NSA-A/ACS2, NSA-A/ASCS2 and NSA-A/ASCS2-L.
Normal Loads
With power on, turn the 15-turn adjustment potentiometer clockwise until the Red LED turns on and stop immediately.
Clockwise is referenced with the terminal block location on the right. The adjustable current switch is now tripped. The
adjustable current switch Hysteresis (Dead Band) is 10% of the trip point typically.
Clockwise = Decrease Trip
Counter-clockwise = Increase Trip
Troubleshooting
Problem
Solution
LED is on but the current switch didn’t activate
Disconnect the wires from the current switch output.
Measure the resistance across the contacts with an
Ohmmeter. See Specifications table for the actual
resistance readings for an open or closed switch reading.
LED didn’t turn on and the current switch didn’t
activate
Verify that the current flowing in the conductor being
monitored is above the fixed trip point as listed in the
operating specifications. If the sensor is monitoring less
than the fixed trip point, see Figure 3.
LED not on but the Current Switch is Activated
LED not indicating correctly, may have been damaged.
Current Switch is operating at a low-level current or
failing to operate within the accuracy specifications
For NSA-A/ASCS2 Series, visually check the mating parts
of the core to ensure there is no debris between the split
contacts. Remove all debris or dust manually and close
the current sensor, see Figure 2. Retest the sensor in your
application.