Wieland SNA-4053-K-A Safety Relay

SNA: Safety switch monitoring series (for monitoring emergency stop, safety gates, safety light curtains)

4053: Specification code

K: Pluggable screw terminals

A: Supply voltage AC/DC 24 V

Suffix differentiation for the series:

A = AC/DC 24 V; C = Push-in spring terminals; KM = Automatic reset; KE = Special version

2. Core Specifications & Safety Ratings
3. Safety Certifications

PL e / Category 4 (EN ISO 13849-1)

SIL CL3 (EN 62061)

2. Contact Configuration

3 safety normally open contacts (13-14 / 23-24 / 33-34)

1 normally closed signal contact (41-42)

3. Electrical Data

Supply: 24 V AC/DC

Continuous rated current Ith: 8 A

AC-15: 230 V / 5 A; DC-13: 24 V / 5 A

Mounting: DIN 35 mm rail; Width 22.5 mm

4. Input Functions

Dual-channel safety circuit (S11/S12, S21/S22)

Supports cross-channel short-circuit monitoring

Manual reset (with reset monitoring)

Suitable for: Emergency stop buttons, safety gate switches, magnetic safety switches, safety light curtains

3. Typical Wiring Logic
4. A1(+), A2(-): 24 V power supply
5. S11-S12, S21-S22: Dual-channel safety devices (normally closed signal)
6. S33-S34: Reset terminals (connect external normally open reset button; shorted = automatic reset)
7. 13-14 / 23-24 / 33-34: Safety outputs (for controlling main contactors)
8. 41-42: Normally closed fault feedback signal
9. Model Correction & Alternative Reference

⚠️ The most frequently confused model on the market: SNA4043K-A (4043, easily mistaken for 4053)

⚠️ Important Verification Conclusion

SNA4053K-A is NOT an official standard model in Wieland catalogues, it is highly likely a transcription error:

1. Most common miswriting: SNA4043K-A (Part No. R1.188.1810.0)

Automatic reset, no reset monitoring; dual-channel with short-circuit monitoring

2. Alternative similar model: SNA4063K-A

Manual reset (with reset monitoring) — this is the core difference from SNA4043

Model rules:

SNA4043K-A: Automatic reset

SNA4063K-A: Manual reset (reset button monitoring)

Both models share identical contact configuration, safety rating and dimensions; only reset logic differs.

Quick Selection Comparison Table

Recommended Actions

1. Verify the printed model on the physical nameplate of the unit;
2. Confirm site requirements: Reset monitoring required or not

Emergency stop circuits generally require manual reset (SNA4063K-A)

Safety light curtain applications may adopt automatic reset (SNA4043K-A)

Application Scenarios of Wieland SNA Series Safety Relays (SNA4043 / SNA4063)

This series achieves PL e / Cat.4 / SIL3 with dual-channel monitoring, primarily deployed for safety circuits on machine tools and automated production lines. Content is divided into supported safety signal types, industry applications, and key selection differentiation.

1. Supported Safety Input Signals (Hardware Utilization)
2. Emergency stop buttons (dual normally closed contacts)

Most common application: Machine main emergency stop and zone emergency stop circuits.

Standard requirement: Emergency stop circuits prefer SNA4063K-A (manual reset with monitoring).

2. Safety gate switches / Magnetic safety sensors

Interlock for protective doors, maintenance doors and perimeter fencing; power circuit cutout upon door opening.

3. Safety light curtains

Hazard zone intrusion protection for presses, conveyor lines and robot stations.

Light curtain solutions commonly use SNA4043K-A (automatic reset).

4. Two-hand control devices

For stamping and riveting equipment, preventing single-hand access to hazardous zones.

5. Safety mats, safety bumpers

Perimeter intrusion detection around robot cells, automatic doors and lifting platforms.

2. Major Industry & Equipment Applications

(1) Machine Tool Industry

CNC lathes, machining centres, grinders, punching machines, bending machines

Application: Protective door interlock, emergency stop circuits, safety light curtain protection

(2) Automated Production & Packaging Equipment

Packaging machines, palletizers, conveyor lines, sorting equipment, labellers

Robot workstations, gantry robot safety fence interlock

(3) Rubber & Plastics Industry

Injection moulding machines, extruders, blow moulding equipment: Safety gates, emergency stop, safety light curtains

(4) Logistics & Warehousing Equipment

Automated warehouses, lifts, shuttles, sorting lines

Lifting platforms, dock leveller safety interlocks

(5) New Energy & Lithium Battery Equipment

Cell assembly machines, electrolyte filling machines, sealing equipment, test tooling

Wieland products are widely adopted on export machinery to meet EU CE Machinery Directive requirements

(6) Woodworking & Printing Machinery

Panel saws, cutting machines, printing presses, die-cutting machine safety protection

(7) General Custom Automation

Custom test fixtures and assembly machines; deployed as core safety logic unit to cut off main contactors and servo power circuits.

3. Critical Application Selection Comparison

⚠️ SNA-4053-K-A is not an official Wieland standard model. It is almost certainly a nameplate transcription error; physical unit will be one of the two above variants.

4. Limitations & Unsuitable Applications
5. Cannot directly drive high-power loads; safety contacts are intended to control contactor coils, not motors directly
6. Not suitable for solenoid valves or high-frequency switching loads
7. Cannot satisfy safety requirements higher than PL e / Cat.4 (this series already reaches Cat.4 maximum rating)

Selection Guidelines for Wieland SNA / SNO Safety Relays

Based on the SNA4043 / SNA4063 platform covered above; structured criteria ready for engineering proposals and procurement checks.

Step 1: Confirm Required Safety Rating (Mandatory Priority)

Compliant with ISO 13849-1 / EN 62061

1. PL & Category

PL e / Cat.4: Highest rating. For high-risk stations including robots, stamping, injection moulding, machine tools and lithium battery equipment (supported by all mainstream SNA variants)

PL d / Cat.3: Low-risk general automation and conveyor lines

2. SIL Level

SIL 3 corresponds to PL e; preferred for machinery exported to EU

✅ Selection Rule: Do NOT downgrade safety rating for high-risk equipment.

Step 2: Determine Safety Input Channel Configuration (Dual Channel Is Standard)

Channel Modes

Dual-channel monitoring with cross short-circuit detection: Industry standard, fitted across all SNA variants. Compatible with dual normally closed safety devices (E-stop, safety gates, light curtains)

Single channel: Only permitted for low-risk scenarios; available on selected SNO variants. NOT allowed for high-risk machinery.

Compatible Sensor Types

Emergency stop switches, mechanical safety gates: Dual normally closed (NC)

Magnetic safety switches, safety light curtains: Dual NC / OSSD signals

⚠️ Two types of safety light curtains:

① OSSD solid-state output → Requires relay model supporting OSSD input

② Light curtain with relay converted contact output → Compatible with standard SNA4043 / SNA4063

Step 3: Reset Mode (Most Common Source of Wrong Selection!)

Key Distinction:

Monitored reset detects open or short circuits on reset wiring and triggers safety lockout for superior safety. Simple unmonitored manual reset should be avoided on new projects.

Step 4: Supply Voltage

Main Wieland options:

Suffix A = AC/DC 24 V (Automation standard, selected in 90% of projects)

Less common: 110 VAC, 230 VAC — only for legacy retrofits

Example: SNA4063K-A → A = AC/DC 24 V supply

Step 5: Terminal Type (Identified by Suffix K / C)

K = Pluggable screw terminals

Advantages: Vibration resistant, ideal for permanent cabinet installation and on-site maintenance (the unit in your photo uses K terminals)

C = Push-in spring terminals

Advantages: Fast wiring without screwdrivers; use cautiously under heavy vibration

Example: SNA4063K-A

Step 6: Output Contact Configuration

Main Safety Outputs (For Power Circuit Cutoff)

SNA4043 / SNA4063: 3 normally open safety contacts

Purpose: Wired in series with main contactor coils for redundant shutdown

Auxiliary Signal Contacts (PLC Feedback)

1 built-in normally closed fault contact

Opens upon safety activation or relay fault; used for alarm indicators and PLC signalling

Selection Note: If multiple feedback signals are required, add auxiliary relays. Safety contacts should not be expanded externally.

Contact Load Ratings

AC-15: 230 V / 5 A

DC-13: 24 V / 5 A

👉 Never drive motors directly; only control contactor coils!

Step 7: Mounting & Physical Specifications

1. Mounting: Standard DIN 35 mm rail
2. Width: SNA40xx series 22.5 mm, compact design saving cabinet space
3. Environmental rating: IP20 (for cabinet installation only; not for outdoor direct deployment)

Step 8: Differentiate SNA vs SNO Series (Frequent Confusion)

SNA Series: Dual-channel safety monitoring, up to PL e Cat.4; for emergency stop, safety gates, light curtains (your target series)

SNO Series: Predominantly single channel, lower safety rating generally PL d and below; low-cost basic solutions

Common Selection Pitfalls Checklist

1. ❌ Misapplication: Using automatic reset SNA4043 for emergency stop circuits — violates machinery safety standards, fails third-party audit & CE certification
2. ❌ Transcription error SNA-4053-K-A: No official model; physical unit is either SNA4043 or SNA4063
3. ❌ Direct drive of solenoid valves or high-power loads with safety contacts → contact burnout and loss of safety function
4. ❌ Mixing K screw terminals and C spring terminals, leading to mismatch on delivery
5. ❌ Ignoring reset monitoring requirements → machine fails acceptance testing

Rapid Selection Workflow (For Field Engineers)

1. Identify safety device: Emergency stop / safety gate → select SNA4063xx-A (monitored manual reset); Light curtain / safety bumper → SNA4043xx-A (automatic reset)
2. Confirm supply voltage: Default AC/DC24V suffix A
3. Select terminal type: Permanent cabinet installation → K screw terminal; high volume assembly for fast wiring → C spring terminal
4. Verify safety rating: High-risk equipment requires PL e / Cat.4 / SIL3
5. Confirm number of safety contacts sufficient for contactor control

Complete Official Model List of Wieland SNA40xx Safety Relays

Series Profile: safeRELAY SNA40xx dual-channel safety monitoring, PL e / Cat.4 / SIL3, DIN rail mounting;

⚠️ Important Notice: SNA-4053-K-A is NOT an official Wieland model, it is a transcription error. Official core variants are limited to 4043 / 4044 / 4063 / 4064;

Industry standard: Suffix A = AC/DC24 V (automation default). Specify A suffix for new orders.

1. Model Naming Rules

`SNA 40XX [Terminal][Reset]-[Voltage Suffix]`

1. SNA: Dual-channel safety monitoring base unit
2. 40XX:

4043: 3 safety NO contacts, automatic reset (no reset monitoring)

4044: 4 safety NO contacts, automatic reset (no reset monitoring)

4063: 3 safety NO contacts, manual reset (with reset circuit monitoring)

4064: 4 safety NO contacts, manual reset (with reset circuit monitoring)

Last digit 3 = 3 safety NO contacts; Last digit 4 = 4 safety NO contacts

3. Terminal Code

K: Pluggable screw terminals (most widely used in projects)

C: Pluggable Push-in spring terminals

4. Extended Reset Suffix (KM/KE)

KM: Simple manual reset without monitoring; rarely specified for new projects

5. Voltage Suffix

A: AC/DC 24 V (automation standard)

No suffix: Fixed screw terminals (legacy models, phased out)

2. Mainstream Models for Domestic Projects (24 V AC/DC)

SNA4043 Series | Automatic Reset, 3 Safety NO Contacts

SNA4044 Series | Automatic Reset, 4 Safety NO Contacts

SNA4063 Series | Manual Reset (Monitored), 3 Safety NO Contacts【Preferred for Complete Machinery】

SNA4064 Series | Manual Reset (Monitored), 4 Safety NO Contacts

3. Legacy Non-Standard Voltage Models (Only For Equipment Replacement, Not Recommended For New Projects)

Fixed non-pluggable screw terminals (no suffix A)

SNA4043K: AC42~48 V / AC115 V / AC230 V

SNA4063K: AC230 V

Note: All new domestic machinery shall adopt AC/DC24 V models with suffix -A

4. General Specifications Applicable to All Variants
5. Safety Rating: PL e / Cat.4, SIL 3 (EN ISO13849-1, EN62061)
6. Contact Ratings: AC-15 230 V/5 A; DC-13 24 V/5 A
7. Mounting: DIN 35 mm rail; Width 22.5 mm; IP20 (Cabinet installation only)
8. Features: Dual-channel cross short-circuit monitoring, EDM external device monitoring support, 3 status LED indicators
9. Wiring: Supports single-channel / dual-channel connection modes
10. Quick Selection Summary Table

6. Procurement Reminders
7. If customer submits model `SNA-4053-K-A` → Confirm transcription error immediately. Check physical nameplate; the actual unit is almost certainly SNA4063K-A.
8. Always include complete model + manufacturer part number in BOM to avoid delivery mismatch between K screw terminals and C spring terminals.
9. Do not interchange automatic reset SNA4043 and monitored manual reset SNA4063; incorrect selection will lead to failed safety acceptance.
10. Contact count selection: 3 contactors or less → SNA4063; ≥4 contactors requiring synchronous shutdown → select SNA4064.