BS EN 12101-10 is the European standard specifying requirements for power supplies used in smoke and heat control systems (SHCS). It defines performance criteria for battery backup units (BBUs) connected to AOV control panels, including charging capacity, standby duration, load testing, and environmental resilience. All power supplies for AOV systems installed in the UK should conform to this standard.

What Is BS EN 12101-10?

BS EN 12101-10:2005 — “Smoke and heat control systems — Part 10: Power supplies” — is part of the BS EN 12101 suite of standards that covers all components of smoke ventilation systems. While other parts of the standard address natural smoke vents (Part 2), mechanical extract systems (Part 3), and control components (Part 9), Part 10 deals specifically with the electrical power supply that drives the system.

AOV systems must maintain operation even during a mains power failure — which is a common consequence of fire. The battery backup unit is the insurance policy that keeps vents opening, dampers operating, and control panels functioning when mains power is lost.

Key Requirements of BS EN 12101-10

Standby Duration

The standard requires that the power supply maintains full system operation for a minimum period after mains failure. For AOV systems, the required standby duration is typically 72 hours of standby followed by 60 minutes of full activation — though the fire engineer may specify a longer duration based on the fire strategy. This ensures the system remains operational throughout a prolonged incident and the subsequent building investigation period.

Battery Charging

The charger within the BBU must be capable of recharging depleted batteries to 80% capacity within 24 hours. This ensures the system is restored to near-full resilience quickly after an incident or a prolonged mains outage. The charger must also prevent overcharging, which can damage lead-acid or sealed maintenance-free (SMF) batteries.

Load Capacity

The BBU must supply the full rated load of the connected AOV system — including the control panel, actuators, detectors, and any ancillary devices — under battery power alone. The unit must be sized to match the total current draw of the system, with a safety margin. Undersized BBUs are a common installation fault that causes system failure during real fire events.

Environmental Performance

BS EN 12101-10 specifies operating temperature ranges (typically -5°C to +40°C for internal units), humidity resistance, and vibration tolerance. BBUs installed in plant rooms, roof spaces, or external enclosures must be rated for the ambient conditions they will encounter.

Monitoring and Fault Indication

The standard requires that the power supply monitors battery condition and signals faults to the control panel. Fault conditions include: mains failure, low battery, battery disconnection, and charger fault. These signals must be distinguishable from fire signals so that building managers can respond appropriately.

Choosing the Right Battery Backup Unit

Selecting a BBU for an AOV installation involves calculating the total current draw of the system and matching it to a unit with sufficient ampere-hour (Ah) battery capacity. Common sizes are 4 A, 8 A, 13 A, and 20 A output ratings, with battery packs sized for the required standby duration.

AOV Direct stocks a range of BS EN 12101-10-compliant battery backup units:

  • Ventec S404 — 4 A output, suitable for single-zone systems with low actuator count
  • Ventec S408 — 8 A output, mid-range capacity for medium-sized installations
  • Ventec S420 — 20 A output, maximum capacity for large multi-zone systems

All units include integral battery charging, mains failure monitoring, and fault output compatible with standard AOV control panels. View the full battery backup range.

Installation and Testing

BS EN 12101-10 does not specify installation method in detail, but the BBU must be installed by a competent electrician familiar with fire protection systems. The unit should be located in a protected area (not within the fire compartment it serves), connected to a dedicated mains supply, and accessible for battery replacement and testing.

On completion, the system must be commissioned to confirm that the BBU correctly monitors mains status, charges the battery, signals faults, and supplies the full load under battery power. Testing records should be retained as part of the building’s fire safety documentation.

Frequently Asked Questions

Does every AOV system need a battery backup unit?

Yes. Approved Document B and BS 9991 both require that AOV systems remain operable under mains power failure. A BS EN 12101-10-compliant BBU is the standard means of achieving this. The only exception is very small natural ventilation systems where manual operation is acceptable — but these are rare in regulated buildings.

How long do AOV batteries last?

Sealed lead-acid batteries used in AOV BBUs typically have a design life of 3–5 years. After this period, capacity degrades and the battery may no longer meet the required standby duration. Batteries should be replaced every 3–5 years as part of the system’s planned maintenance programme.

What amperage BBU do I need?

The required output current equals the total quiescent current of all connected devices plus the peak activation current when all actuators operate simultaneously. Your AOV system designer or the actuator datasheets will provide the figures needed to make this calculation. When in doubt, size up — an oversized BBU is always better than an undersized one.