BS EN 50131 Compliance Guide for Intruder Alarms

# BS EN 50131 Compliance Guide for Intruder Alarms

Complete guide to compliance with BS EN 50131-1:2006+A3:2020 for security installers and engineers.

## Overview

BS EN 50131-1 is the European standard for intruder alarm systems. Compliance is often required for insurance, police response, and professional certification. This guide covers the essential requirements for installers.

## Security Grades

### Grade 1 – Low Risk
– **Risk Level:** Low
– **Application:** Residential, low-value premises
– **Intruder:** Opportunist with limited knowledge
– **Tools:** No special tools
– **Response Time:** Extended (up to 30 seconds)

**Requirements:**
– Basic detection
– Local alarm only (optional remote)
– Battery backup: 8 hours minimum
– Tamper protection: Basic

### Grade 2 – Low to Medium Risk
– **Risk Level:** Low to medium
– **Application:** Residential/commercial, moderate value
– **Intruder:** Some knowledge of alarm systems
– **Tools:** Limited portable tools
– **Response Time:** Medium (up to 20 seconds)

**Requirements:**
– Motion detection + door contacts
– Remote monitoring recommended
– Battery backup: 12 hours minimum
– Tamper protection: Enhanced

### Grade 3 – Medium to High Risk
– **Risk Level:** Medium to high
– **Application:** Commercial, high value
– **Intruder:** Sophisticated, plans attack
– **Tools:** Full range of tools, electronic aids
– **Response Time:** Short (up to 15 seconds)

**Requirements:**
– Multi-layer detection
– Remote monitoring required
– Battery backup: 24 hours minimum
– Tamper protection: High level
– Dual signaling recommended

### Grade 4 – High Risk
– **Risk Level:** Very high
– **Application:** Banks, jewelry, critical infrastructure
– **Intruder:** Professional, bypasses alarms
– **Tools:** Full range, specialist equipment
– **Response Time:** Immediate (up to 10 seconds)

**Requirements:**
– Maximum detection coverage
– Remote monitoring mandatory
– Battery backup: 48+ hours
– Tamper protection: Maximum
– Dual signaling mandatory

## Environmental Classes

### Class I – General Indoor
– Temperature: -5°C to +40°C
– Humidity: Up to 75% RH
– Application: Normal indoor environments

### Class II – Moderate Indoor
– Temperature: -10°C to +55°C
– Humidity: Up to 93% RH
– Application: Warehouses, factories

### Class III – Severe Indoor
– Temperature: -25°C to +70°C
– Humidity: Up to 93% RH
– Application: Industrial, harsh environments

### Class IV – Outdoor
– Temperature: -35°C to +70°C
– Humidity: Up to 98% RH
– Application: External detection

## Power Supply Requirements

### Mains Supply
– Must be from permanent connection
– Separate circuit breaker recommended
– Label as "Security System – Do Not Switch Off"

### Battery Backup

**Battery Testing:**
– Automatic battery test required (Grades 2-4)
– Low battery warning required
– Battery must sustain at least 80% capacity
– Replace every 3-5 years (or as per manufacturer)

### Battery Calculation Formula
“`
Capacity (Ah) = (Total Current × Backup Hours) / 0.8

Where:
– Total Current = Quiescent + Alarm current
– 0.8 = Derating factor (80% capacity)
– Add 20% safety margin for Grade 3/4
“`

**Example (Grade 3, 24-hour backup):**
– Panel quiescent: 100mA
– Devices quiescent: 200mA
– Alarm current: 500mA
– Average: 350mA
– Calculation: (0.35A × 24h) / 0.8 = 10.5Ah
– Recommended: 12Ah battery minimum

## Detection Requirements

### Coverage Standards

**Grade 1:**
– Door contacts on entry/exit points
– Motion detection in vulnerable areas

**Grade 2:**
– All Grade 1 requirements
– Motion detection in all accessible areas
– Glass break detection (if windows accessible)

**Grade 3:**
– All Grade 2 requirements
– Dual technology detectors (PIR + microwave)
– Perimeter detection
– Ceiling protection

**Grade 4:**
– All Grade 3 requirements
– Multiple detection technologies
– Video verification recommended
– Anti-masking detectors

### Detector Spacing

| Detector Type | Maximum Range | Mounting Height |
|—————|—————|—————–|
| Standard PIR | 12m | 2.0-2.5m |
| Long-range PIR | 18m | 2.0-2.5m |
| Curtain PIR | 6m | 2.0-2.5m |
| Dual-tech | 15m | 2.0-2.5m |
| Microwave | 15m | 2.0-2.5m |

### Pet Immunity
– Grade 1: Basic (up to 25kg)
– Grade 2: Standard (up to 40kg)
– Grade 3: Enhanced (up to 80kg)
– Grade 4: Custom assessment required

## Signaling and Monitoring

### Signaling Grades

### ARC Requirements
– Grade 1-2: Single path acceptable
– Grade 3: Dual path recommended
– Grade 4: Dual path mandatory
– All grades: Test signal every 24 hours minimum

### Police Response
– Grade 1-2: Level 1 (confirmed alarm)
– Grade 3: Level 1 or 2 (dual confirmation)
– Grade 4: Level 3 (immediate response)

## Tamper Protection

### Types of Tampers

**1. Panel Tamper**
– Cabinet lid contact
– Wall mounting contact
– Required: All grades

**2. Cable Tampers**
– End-of-line (EOL) resistors
– Line monitoring
– Required: Grades 2-4

**3. Device Tampers**
– PIR cover contacts
– Contact back boxes
– Required: All grades

**4. Bell/Siren Tampers**
– External siren housing
– Strobe cover
– Required: All grades

### EOL Resistor Values

## Installation Requirements

### Cabling
– Grade 1: Standard alarm cable
– Grade 2: Screened cable recommended
– Grade 3: Screened cable required
– Grade 4: Armored or conduit required

### Cable Routes
– Must be concealed where possible
– Grade 3-4: Cabling within 2m of entry points must be protected
– Grade 4: All cabling in secure zones

### Equipment Locations
– Control panel: Secure location, Grade 3-4 in separate room
– Keypads: Within entry/exit route, Grade 4 requires two-key authorization
– Sirens: Minimum 3m high, visible from outside

## Documentation Requirements

### Mandatory Documentation

**For All Grades:**
1. System design certificate
2. Installation certificate
3. Commissioning certificate
4. User manual
5. Log book

**Additional for Grade 3-4:**
6. Risk assessment
7. System specification
8. Maintenance contract
9. As-fitted drawings

### Certificates

**Design Certificate:**
– Installer details
– Grade and class justification
– Detection coverage plan
– Power calculations

**Installation Certificate:**
– Date of installation
– Equipment list
– Wiring details
– Test results

**Commissioning Certificate:**
– Walk test results
– Signal strength tests
– Battery test results
– User training confirmation

## Testing Requirements

### Initial Commissioning
– Walk test: Every zone
– Battery test: Full discharge simulation
– Signaling test: Verify ARC receives signals
– User training: Document completion

### Routine Testing

### Service Requirements
– Grade 1: As required
– Grade 2: Annual minimum
– Grade 3: Annual minimum
– Grade 4: Bi-annual minimum

## Common Compliance Failures

### Power Supply
– ❌ Battery too small for backup requirements
– ❌ No low battery warning configured
– ❌ Mains supply not dedicated circuit

### Detection
– ❌ Insufficient coverage for grade
– ❌ Wrong detector type for environment
– ❌ Mounting height incorrect

### Signaling
– ❌ Single path for Grade 3/4
– ❌ No test signals for 24+ hours
– ❌ ARC details not programmed

### Documentation
– ❌ Missing installation certificate
– ❌ No user manual provided
– ❌ Log book not supplied

### Testing
– ❌ Walk test not performed
– ❌ Battery test not documented
– ❌ User not trained

## Quick Compliance Checklist

### Pre-Installation
– [ ] Risk assessment completed
– [ ] Grade determined
– [ ] Environmental class confirmed
– [ ] Power calculations done
– [ ] Coverage plan drawn

### Installation
– [ ] All cabling concealed/protected
– [ ] EOL resistors installed correctly
– [ ] Battery sized correctly
– [ ] All tampers connected
– [ ] Equipment labeled

### Commissioning
– [ ] Walk test completed
– [ ] Battery test passed
– [ ] Signaling verified
– [ ] User trained
– [ ] Log book completed

### Handover
– [ ] Installation certificate issued
– [ ] Commissioning certificate issued
– [ ] User manual provided
– [ ] Maintenance schedule agreed
– [ ] ARC confirmed signals

## Related Standards

– **BS EN 50131-2:** Power supplies
– **BS EN 50131-3:** Warning devices
– **BS EN 50131-4:** Transmission systems
– **BS EN 50131-5:** Interconnections
– **BS EN 50131-6:** Power supplies
– **BS EN 50131-7:** Application guidelines
– **PD 6662:** Scheme for installers

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*Last updated: February 2026*
*For qualified security engineers. Always refer to current standards.*