Complete Guide to EN 12845 Sprinkler System Installation

What is EN 12845?

EN 12845 is the European standard governing the design, installation, and maintenance of fixed firefighting sprinkler systems. It applies across all CEN member states, making compliance essential for meeting local fire protection regulations in Belgium, the Netherlands, Germany, Norway, and beyond.

As a company specialising in sprinkler installation subcontracting across Europe, Oskar Sprinkler works with EN 12845 requirements daily. In this article, we share practical knowledge gained from hundreds of projects.

Hazard Classification Under EN 12845

One of the most critical elements of the standard is the hazard classification system, which determines the parameters of the entire installation:

• LH (Light Hazard) — low fire risk environments such as offices, hotels, hospitals
• OH (Ordinary Hazard) — divided into groups OH1 through OH4, covering manufacturing plants, workshops, car parks
• HH (High Hazard) — categories HHP and HHS for warehouses and high fire load buildings

Correct classification is the foundation of any project — errors at this stage lead to under-sizing or over-sizing the system, resulting in unnecessary costs or, worse, ineffective protection.

Discharge Densities and Areas of Operation

For each hazard class, the standard defines minimum discharge density (mm/min) and assumed area of operation (m2). For example:

• LH: 2.25 mm/min over 84 m2
• OH1: 5.0 mm/min over 72 m2
• OH3: 5.0 mm/min over 216 m2
• HHP: up to 12.5 mm/min over 260 m2 depending on category

Water Supply Requirements

EN 12845 provides detailed requirements for the water supply feeding the sprinkler system. The standard specifies:

• Minimum pressure and flow at the most remote sprinkler head
• Required system operating duration (typically 60-90 minutes)
• Types of acceptable water sources: tanks, pumps, direct mains connection
• Requirements for backup water supply

Correct hydraulic calculations are a critical design element ensuring the system performs effectively during a fire event.

Installation — Key Aspects

Based on our experience as specialist installation subcontractors, the most important installation aspects include:

Pipework and Supports

• Pipe sizing in accordance with hydraulic calculations
• Appropriate material selection — black steel, galvanised steel, CPVC (under specific conditions)
• Correct support spacing as per the standard's tables
• Pipe gradients ensuring full system drainage

Sprinkler Head Positioning

The standard precisely defines maximum and minimum distances between sprinkler heads, as well as distances from walls and obstructions. Incorrect head positioning is one of the most common installation errors that can lead to failed commissioning.

• Maximum spacing between heads: dependent on hazard class
• Maximum distance from wall: typically half the inter-head spacing
• Minimum deflector distance from ceiling: 25-300 mm depending on head type

Commissioning and Testing

Upon completion of installation, the system must undergo several tests:

• Pressure test: 15 bar or 1.5 times working pressure (whichever is greater) for a minimum of 2 hours
• Flow test: verification of performance at the most remote sprinkler head
• Alarm test: confirmation of correct signalling operation
• Visual inspection: quality control of installation, labelling, documentation

Common Installation Mistakes Under EN 12845

Based on our extensive experience, the most frequent issues include:

• Insufficient pipe supports and hangers
• Incorrect sprinkler clearance from obstructions (beams, ductwork)
• Missing fire stops at wall and floor penetrations
• Defective pipe joints causing leaks
• Inadequate gradient on branch lines

EN 12845 Compared to Other Standards

It is worth noting that EN 12845 differs from other widely used standards:

• NFPA 13 (American standard) — different hazard classifications and discharge parameters
• VdS CEA 4001 (German/insurance standard) — more restrictive in certain aspects
• FM Global — proprietary requirements, often more stringent

Working across multiple European countries, Oskar Sprinkler understands each market's specific requirements and adapts accordingly.

Conclusion

EN 12845 is a comprehensive document that every fire protection professional must understand. Correct application of the standard demands experience and technical expertise — from hazard classification, through hydraulic calculations, to installation and commissioning.

Looking for an experienced sprinkler installation subcontractor working to EN 12845? Contact Oskar Sprinkler — our team of certified fitters delivers projects across Belgium, the Netherlands, Norway, and Germany. We guarantee top-quality installation, on-time delivery, and full compliance with European standards.