Enclosures and accessories for fire safety

Graham Fox, Managing Director of Spelsberg Els UK, comments on the importance of specifying the correct enclosure and accessories when designing electrical systems for emergency provisions.

While regulations regarding electrical installation and components increase in scope and number, talking to the right supplier at the onset of a project can be the easiest way to save time, money and possibly lives.

When designing cabling systems for commercial and industrial premises it is understandable, considering recent media coverage, that the emphasis may be put on conduit selection using the advice provided by the chosen supplier.

However, in order to meet the relevant health and safety requirements for emergency systems it is essential that all enclosures and cabling accessories also match the performance of these cables.

The safety of people in case of fire can only be guaranteed if all the relevant safety requirements are met for electrical systems that allow fire detectors, lighting, passenger and firemen lifts as well as smoke and heat discharge installations to remain operational for a certain length of time.

According to national fire safety regulations for example, the wiring of critical safety systems such as fire alarms and emergency lighting must operate for at least 30minutes when exposed to external fire.

Other systems such as water pressurising plants for the supply of extinguishing water, ventilators and lifts have to remain functioning for a minimum of 90 minutes.

In order to help comply with these regulations there are a range flame resistant junction boxes provide guaranteed protection to DIN VDE and UL standards.

Aluminium and steel versions that meet these requirements are widely available, but an extensive range of toughened plastic versions can be easily sourced that offer more than adequate circuit protection (up to E90) while being inexpensive and more versatile.

These enclosures are made from halogen-free Duroplast, which improves evacuation conditions for personnel and emergency services by producing low smoke emissions and therefore delaying the build up of harmful fumes in buildings where there is a fire.

The body material and a combination of high temperature ceramic terminals can therefore help guarantee the maintenance of power supplies to emergency systems for a minimum of 90 minutes according to DIN4102 part 12.

Flame resistant plastic cable glands are also available with the enclosures that provide high levels of ingress protection IP65, allowing use in sprinkler, exit lights and general lighting systems for both commercial and industrial premises.

By enabling power supplies to be maintained for a minimum of 90 minutes, operations that involve hazardous substances can also be shut down or neutralised and more time guaranteed for automatic computer backup procedures to be completed.

Evacuation time can be increased and fire damage minimised by fitting E90 rated enclosures in electrical cabinets and junction boxes used for the wiring of fire-fighting installations, compressors houses, smoke hatches and especially lifts.

Such enclosures are also suited to public areas in office blocks for example where they are easily modified to provide obvious circuit information and can be supplied in virtually any colour to match d?cor or colour coded for increased safety in communal systems.

It is in these environments where the versatility of plastic junction boxes and transit systems can provide functional and safety improvements, yet still be aesthetically pleasing.

A good example of this is the next generation of cable transit systems which provide the ease of customisation needed for the constant rewiring required in large computer networks and yet still prevent smoke and flames travelling between rooms.

The units consist of tough galvanised boxes fitted with adaptable face panels and feature internal walls that automatically expand when exposed to excessive heat or flames, providing at least 90 minutes of evacuation time and helping protect emergency systems.

Models are available for all types of walls, ceilings and have the capacity to accept armoured conduits of almost any diameter.

If a cabling system is already in place, but the enclosures used do not conform to current regulations, fire protection hoods are available that are designed for retrofitting over all types of junction boxes.

The hoods work on the same principle as the transit systems, automatically sealing themselves when exposed to heat, protecting the circuitry inside.

The outer casings of the hoods are made from a tough polycarbonate material that is both flame retardant and impact resistant, making them a cost effective option for improving the safety of cabling systems for operations that had been previously overlooked, such as lift and heat discharge installations.

However, even when the correct conduit, enclosures and terminals are installed, accessories such as wall plugs and installation clips can still impair the performance of a system.

Whilst fire proof cables may meet DIN4102 part 12, they are tested in lengths no longer than 2.5m, and if the supports or fixtures fail in an the event of fire, the excess weight upon the junction boxes and cables can cause premature failure.

It is also worth noting that the use of powder coated cable trays or ladders as well as nonarmoured conduit could also have a negative effect on the cables.

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