30A Junction Box 3-Terminal - Black (89mm)

The Knightsbridge SN8430B is a 30A three-terminal junction box with an 89mm diameter thermoset resin case and selective cable entry. Three brass terminals inside the box accept ring or fork cable terminations for creating or extending 230V circuits, typically used for lighting loops, immersion heater supplies, or other fixed wiring applications up to 30A load.

Designed for concealed installation above ceilings, behind plasterboard or within floor voids, the junction box provides a permanent connection point for joining multiple cable runs without the need for a surface-mounted accessory. The selective entry allows cables to be fed in from any point around the circumference by removing the appropriate knockout disc. The 26mm projection keeps the box shallow enough for installation in standard stud walls and plasterboard ceilings with minimal intrusion into the cavity space.

The thermoset resin construction resists impact and provides dimensional stability across temperature changes better than standard thermoplastics, with the material rated to withstand higher continuous operating temperatures typical of 30A circuits. The IP20 rating confirms the box is protected against solid objects larger than 12.5mm but is not sealed against moisture, so it must be installed in dry indoor locations only. The black finish allows the box to blend into dark cavities and reduces visibility if accidentally exposed through access panels.

Product Specification Sheet

What cable size does it accept?

The three brass terminals accept cable conductors up to 6mm² cross-sectional area, which is typical for 30A-rated circuits using 6mm² twin-and-earth or 6mm² singles in conduit. Check the specification sheet for the exact terminal capacity.

Can it be used in bathrooms or outdoors?

No. The IP20 rating means the junction box is not sealed against moisture and must be installed in dry indoor locations only. For bathrooms or outdoor installations, a higher IP-rated enclosure is required.

What does 'selective entry' mean?

Selective entry allows you to remove knockout discs at any point around the circumference to feed cables in from the direction that suits your cable run, rather than being restricted to fixed entry points. This makes installation easier in awkward cavity positions.

Does it need an earth terminal?

The three terminals shown are for line, neutral and circuit connections. If earthing continuity is required, a separate earth terminal block or flying earth connections must be made within the box using an appropriate connector.