Cases & enclosures
BUILDING DESIGN AND INSTALLATION:
ENSURING FIRE SAFETY FOR ELECTRICAL CONNECTIONS
I 20
To protect electrical junctions in buildings from the threat of fire, embedding connections in concrete has been one of the possible solutions in the past, depending on the building design. While concrete is fire resistant, the challenges of access make inspection, as well as installation, more complex to achieve. Instead, fire-protected enclosures mounted directly onto a wall surface can make maintenance and installation significantly faster while maintaining the required safety standards. Chris Lloyd, managing director at Spelsberg UK, explains the advantages of fire-resistant, surface-mounted enclosures.
n the event of a building fire, safety systems must continue operating for a prolonged period. As well as alarms to warn occupants and alert emergency services, lighting must remain active to highlight a safe exit route. Smoke and heat extraction systems might be relied on, as well as water booster systems to supply extinguishers, while dedicated eleva- tors might need to safely transport fire crews. All these systems need electrical power and protec- tion of their supply during a blaze, potentially for an hour or more after a fire has taken hold. To achieve this, cable junctions and distribution boards have histori- cally been designed and embedded within concrete protection. However, installing electrical connections within fire-protected enclosures mounted directly onto walls can offer equivalent protection – and in some cases can provide greater security.
THE CONCRETE CHALLENGE While concrete is fire-resistant, the protection it provides to embedded electrical junctions depends on its thickness, and whether additional insulating materials are used in combination. Moreover, embedded electrical junctions might not sufficiently contain a fire should an electrical failure occur inside a concrete wall. In a case like this, the fire could spread through cavities or reach flammable materials if the integrity of the wall is compromised.
Threats also remain in the longer term. In the event of any high temperatures, concrete can conduct heat and retain it over an extended duration, suffi- cient to degrade or damage any enclosed electrical connections. Embedded electrical connections could also be exposed to hidden moisture or damp condi- tions, which could corrode and damage junctions. However, to deal with either of these situations, the
inherent challenge of embedded systems is inspec- tion: the only way to make a visual check is to drill in or completely expose the electrical junction.
FIRE-RESISTANT POLYCARBONATE Using enclosures manufactured from specially treated polycarbonate resistant to flame and heat can protect electrical junctions in the event of a fire. As polycarbonate is non-conductive during fire or heat exposure, the enclosures also prevent the risk of short circuit. Protection features such as ceramic terminal blocks inside the enclosure, resistant to high heat, also help to protect the connections.
Combining these features in a surface-mounted enclosure can ensure electrical integrity for up to 90 minutes, according to the E30-E90 electrical functional integrity standard. This testing and recognition are the hallmark for fire-and heat-pro- tected enclosures like the Spelsberg WKE Lifeline
November 2024 Instrumentation Monthly
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