Schneider CA4KN31BW3 Control Relay

CA4KN: TeSys K series control relay

31: Contact configuration: 3 NO + 1 NC

B: 24 V DC low-consumption coil with built-in bidirectional freewheeling diode

W3: Screw clamping terminals

Core Technical Parameters

Coil: 24 V DC low-power coil, integrated bidirectional peak suppression diode

Contact arrangement: 3 Normally Open + 1 Normally Closed (3NO+1NC), 4-pole

Conventional thermal current Ith: 10 A (at 50 °C)

Rated insulation voltage Ui: 690 V

Utilisation category: AC-15 / DC-13 (standard control circuit loads)

Mounting: DIN35 rail mounting or base plate fixing

Wiring: Screw terminals, tightening torque 1.3 N·m

Dimensions: W45 mm × H58 mm × D57 mm

Mechanical endurance: 20 million operations

Recommended protection: 10 A gG fuse

Origin: Indonesia

Typical Applications

PLC digital output expansion, signal isolation & transfer, logic interlocking, indicator lamp driving, small solenoid/coil actuation. It is an auxiliary control relay, not intended for high-power main circuits. It shares the same footprint as TeSys K contactors and can be installed side-by-side.

Cross-reference for Replacement & Selection

CA4KN22BW3: 2NO+2NC, 24 V DC, screw terminals

CA4KN40BW3: 4NO, 24 V DC, screw terminals

CA4KN31BN3: Spring-cage terminal version (replaces W3)

Customs HS Code

HS code: 85364190 (Electromagnetic relays, rated voltage ≤60 V)

Common Replacements

Domestic alternatives: Chint / Delixi 24 V DC control relays with 3NO+1NC contact configuration.

Schneider direct upgrade: other coil variants within the CA4KN series (e.g., 110 V DC).

Typical Application Cases for CA4KN31BW3 (3NO+1NC, 24 V DC Low-Consumption Control Relay)

Key advantages: built-in bidirectional freewheeling diode, low coil power consumption, direct PLC DO driving; 3NO+1NC allows 3 output channels plus 1 feedback channel; AC-15/DC-13 rated, max operating frequency: 180 cycles per minute.

Case 1: PLC Digital Output Port Expansion (Most Common)

Scenario: Insufficient PLC DO points; DO ports have low current capacity (<0.5 A) and need to drive multiple contactor coils and solenoid valves simultaneously.

Wiring: PLC 24 V DO connected to relay coil terminals A1/A2

Contact assignment:

NO1: Drive LC1D contactor coil

NO2: Drive 24 V DC solenoid valve

NO3: Run indicator lamp

NC1: Feedback to PLC DI for relay status monitoring (wire break / contact sticking diagnosis)

Highlights: Low-power coil avoids overloading PLC outputs; built-in diode eliminates external surge suppression circuits; same TeSys K form factor for neat cabinet layout, standard panel builder solution.

Industries: Machine tools, packaging machinery, assembly line control cabinets.

Case 2: Auxiliary Logic Interlock & Status Collection for Main Contactors

Scenario: Main LC1D contactors have insufficient built-in auxiliary contacts; additional interlocking, fault feedback and on/off indication are required.

Driving signal: Emergency stop circuit / safety relay output energises the CA4KN coil

Contact assignment:

NO1: Enable forward rotation circuit

NO2: Enable reverse rotation circuit

NO3: Contactor ON run lamp

NC1: Wired into reverse circuit for hardware interlock (prevents simultaneous forward & reverse operation)

Note: This is only control-circuit interlocking and cannot replace main-circuit electrical interlocks.

Industries: Conveying equipment, small lifting mechanisms, fan & pump control panels.

Case 3: Fan & Damper Interlock Control for HVAC Air Handling Units

Scenario: DDC controller outputs control damper actuators, fan contactors and alarm lamps, with one status feedback channel to the building BA system.

Driving signal: 24 V DC output from DDC energises CA4KN31BW3

Contact assignment:

NO1: Damper open command

NO2: Fan contactor coil

NO3: Running status lamp

NC1: DI input to BA system for stop / fault feedback

Advantages: High noise immunity with built-in diode, suitable for frequent switching in weak-current building control loops; wide operating temperature range (-25 °C ~ +50 °C) for indoor plant rooms.

Industries: Building automation, clean air conditioning, fresh air handling units.

Case 4: Primary & Standby Pump Rotation Control Relay

Scenario: Level controller / PLC output switches main pump, standby pump and alarm circuits with independent status feedback.

Logic: High water level signal energises the relay coil

NO1: Main pump start

NO2: Standby pump activation (coordinated with delay circuit)

NO3: Overflow alarm lamp

NC1: Relay fault detection signal to PLC

Industries: Sewage lifting, water treatment, water supply control panels.

Case 5: Signal Expansion after Safety Relay Outputs

Scenario: XPS safety relay has limited output contacts; safety OK signals need to be duplicated to inverter enable, alarm and HMI status channels.

Driving signal: Safety relay OK output energises CA4KN coil

NO1: Inverter STO / enable signal

NO2: Safety OK indicator lamp

NO3: HMI DI safety status input

NC1: Safety circuit trip alarm

Critical reminder: Safety judgment remains the responsibility of the XPS safety relay; CA4KN only serves as signal transfer and cannot be used as a safety component alone.

Industries: Automated production lines, robot peripherals, cutting machinery.

Case 6: Isolated Passive Signal Transfer for Variable Frequency Drives / Soft Starters

Scenario: VFD relay output is a dry contact; multiple isolated signals need to be sent to PLC, local alarms and data loggers, with mixed AC/DC circuits.

Driving signal: VFD “Run” dry contact controls the relay coil

NO1: PLC DI running signal

NO2: Local AC220 V run indicator

NO3: Remote SCADA transmission signal

NC1: Stop status signal

Value: Galvanic isolation between 24 V coil side and contact side, preventing electrical noise from coupling into the VFD mainboard.

Selection & Application Best Practices (Frequent Engineering Pitfalls)

1. Load type: Only for control circuit loads (contactor coils, solenoids, indicator lamps); never for main power circuits. Rated thermal current: 10 A, utilisation category AC-15.
2. Coil note: BW3 = 24 V DC low-consumption with built-in bidirectional diode. Do NOT add external LAD4RC surge suppressors, as specified in Schneider official documentation.
3. Terminals: W3 = screw terminals; spring-cage alternative: CA4KN31BN3.
4. Contact logic for 3NO+1NC: 3 output channels + 1 feedback channel, the most widely used contact allocation for automation panels.
5. Mounting: DIN35 rail installation; can be mounted side-by-side with LC1K contactors for consistent cabinet layout.

TeSys K Control Relays (CA2KN / CA3KN / CA4KN) – Full Model Coding Rule

Full model format: CAu KNvw + voltage code + terminal suffix

1. u = Coil Type

CA2KN: AC coil (50/60 Hz)

CA3KN: Standard DC coil (normal power consumption)

CA4KN: Low-consumption DC coil (built-in bidirectional freewheeling diode, PLC direct drive preferred; CA4KN31BW3 falls into this category)

2. vw = Contact Combination (only 3 fixed configurations)

40: 4NO (4 Normally Open)

31: 3NO+1NC (3 Open + 1 Closed, most popular)

22: 2NO+2NC (2 Open + 2 Closed)

3. Voltage Code + Terminal Suffix (Key Part)

W3: Screw clamping terminals

N3: Spring-cage terminals

Suffix “3” = built-in surge suppression diode

Contact Configurations (Only 3 Options for the Whole Series)

1. 40 = 4NO
2. 31 = 3NO+1NC (CA4KN31BW3 uses this configuration)
3. 22 = 2NO+2NC

Full Model List: CA4KN Low-Consumption DC Coil (PLC Version, Built-in Diode)

Coil: DC low power, integrated bidirectional freewheeling diode; Terminals: W3 screw / N3 spring cage

1) 24 V DC (Most Popular: BW3 / BN3)

2) 48 V DC (EW3 / EN3)

CA4KN40EW3 / CA4KN40EN3

CA4KN31EW3 / CA4KN31EN3

CA4KN22EW3 / CA4KN22EN3

3) 72 V DC (SW3 / SN3)

CA4KN40SW3 / CA4KN40SN3

CA4KN31SW3 / CA4KN31SN3

CA4KN22SW3 / CA4KN22SN3

Note: CA4KN series only offers 12/24/48/72 V DC low-consumption variants; no AC coil versions. CA4KN was discontinued at the end of 2024; new projects shall adopt CA3KN models with suffix “3” as direct replacements.

CA3KN Standard DC Coil (Normal Power, Built-in Diode Suffix “3”)

Voltage Codes (Screw: BD/ED/FD…; Spring: BD3/ED3…)

12 V DC: JD / JD3

24 V DC: BD / BD3 (Top replacement: CA3KN31BD3 for CA4KN31BW3)

48 V DC: ED / ED3

110 V DC: FD / FD3

125 V DC: GD / GD3

220 V DC: MD / MD3

Full Model Examples (3 Contact Types)

1. 24 V DC screw terminals (with built-in diode)

CA3KN40BD3 (4NO)

CA3KN31BD3 (3NO+1NC, direct replacement for CA4KN31BW3)

CA3KN22BD3 (2NO+2NC)

2. Spring-cage terminals: keep the voltage code unchanged, only adjust terminal suffix; e.g., CA3KN31BD3 (screw) and spring-cage variant share the same voltage code.

CA2KN AC Coil (50/60 Hz, Main Control Circuits)

Common Voltage Codes

24 V AC: B7

48 V AC: E7

110 V AC: F7

220/230 V AC: M7 / P7 (most used: CA2KN31P7)

380 V AC: Q7

Full Contact Models (AC Coil)

4NO: CA2KN40B7 / CA2KN40P7

3NO+1NC: CA2KN31B7 / CA2KN31P7

2NO+2NC: CA2KN22B7 / CA2KN22P7

Terminal Differentiation (W3/N3 vs Non-Suffix “3”)

1. W3 = Screw clamping terminals (CA4KN31BW3)
2. N3 = Spring-cage quick connect terminals (replacement: CA4KN31BN3)
3. Models without trailing “3”: No built-in diode; external RC snubber is mandatory for DC circuits – not recommended for direct PLC DO driving.

Discontinuation Replacement Solution (Field Retrofit)

Original model: CA4KN31BW3 (24 V DC low-consumption, 3NO+1NC, screw terminals)

✅ Direct drop-in replacement: CA3KN31BD3 (24 V DC standard coil + built-in diode, 3NO+1NC, screw terminals; identical footprint, plug-and-play interchange)

General Technical Specifications (Uniform for All TeSys K Control Relays)

Contact utilisation category: AC-15 / DC-13 (control circuit only)

Conventional thermal current: 10 A (at 50 °C)

Rated insulation voltage: 690 V

Mounting: DIN35 rail or base plate fixing

Overall width: 45 mm, same form factor as LC1K contactors for side-by-side mounting

Mechanical endurance: 20 million operations