5A Junction Box 4-Terminal - Black (59mm)

The Knightsbridge SN8400B is a 5A junction box with four brass terminals housed in a 59mm diameter black thermoset resin casing. The selective entry design allows cables to enter from any point around the perimeter, with unused entry points remaining sealed to maintain the IP20 rating.

Designed for low-current lighting circuits, the junction box provides a concealed connection point for distributing power to ceiling roses, wall lights and pendant fittings. The 5A rating suits typical lighting loads and the 25mm projection allows it to fit inside most ceiling voids and wall cavities without obtrusion. The screw terminals accept cable cores up to 1.5mm² cross-section.

The thermoset resin construction provides better heat resistance than standard thermoplastic junction boxes, making it suitable for installation in loft spaces where summer temperatures can exceed 40°C. The black finish conceals the box when installed in visible locations such as brick outbuildings, workshops and utility rooms. The box carries BS EN 60670 certification and a 25-year warranty.

Product Specification Sheet

What cable size does it accept?

The four brass terminals accept cable cores up to 1.5mm² cross-section, which is standard for UK domestic lighting circuits rated at 5A or 6A.

How does the selective entry work?

The box has pre-formed knockout points around the perimeter. You remove only the knockouts you need for cable entry, leaving the others intact to maintain the IP20 rating and prevent dust ingress.

Can this be used outdoors?

No. The IP20 rating means the box is suitable for dry indoor use only. For outdoor lighting circuits you need a junction box with IP54 or higher rating.

What's the difference between thermoset and thermoplastic?

Thermoset resin maintains its shape at higher temperatures than thermoplastic. This makes it more suitable for loft spaces and other locations where the ambient temperature can exceed 40°C during summer months.