27.1 Commentary

1. Applicability:

● Some recommendations for wired systems are unsuitable for radio-linked systems, especially regarding power supplies and fault monitoring.

● Additional recommendations ensure the integrity and performance of radio communication links between components and the control and indicating equipment (CIE).

2. System Reliability:

● Good system design aims to reduce the probability of inoperability during a fire.

● Hardwired and radio-linked systems have different advantages and disadvantages, making careful site assessment and technology choice crucial.

3. Components:

● Radio-linked components include fire alarm devices, detectors, and manual call points.

● Excessive testing and drills can reduce the battery life of radio-linked sounders.

● Automatic silencing of sounders should not impair audible warnings and should reactivate with new fire commands.

4. Relay Units:

● Radio relay units extend the system range and can form networked systems when they include separate control and indicating panels.

5. Temporary and Permanent Installations:

● Radio communications can link a small number of components to a wired system and are used in temporary installations during construction or refurbishment.

● The standard’s recommendations apply equally to integral radio-linked systems.

27.2 Recommendations

The following recommendations are applicable.

1. Conformance:

● Components should conform to BS EN 54-25.

2. Power Supply:

● Radio-linked components must have two independent power supplies (e.g., mains plus reserve battery, primary plus secondary battery).

● Components may use batteries for normal power.

● A fault warning must be given at the CIE if power can sustain a component for no more than 30 days, plus 30 minutes in alarm condition.

3. Antenna Cables:

● External antenna cables should be monitored for faults, with a fault warning at the CIE within 300 seconds.

● Critical signal path antenna cables should meet fire resistance recommendations, or be protected/routed through low-risk areas.

4. Sounders and Indicators:

● Automatic silencing of sounders should meet specific requirements.

● Visual indicators at detectors should remain illuminated for at least 20 minutes after initiation unless manually reset.

5. Radio Survey:

● A comprehensive radio survey should be conducted before installation to check for interference, signal strength, and background noise.

● Records of signal strength and noise levels should be kept.

6. Survey Equipment:

● Only manufacturer-approved and calibrated survey equipment should be used.

7. Commissioning and Records:

● During commissioning, record system coding, channel/frequency, and signal levels.

● Maintain records of signal levels for each routine service visit.

● Signal levels must meet manufacturer specifications, with remedial action taken if necessary.

● Keep a copy of signal levels on-site with the system logbook.

27 Radio-linked systems