20A Junction Box 4-Terminal - White (79mm)

The Knightsbridge 20A junction box provides four terminals rated for 20A circuits within a 79mm diameter white thermoset resin housing. The selective entry design allows cables to be introduced through knock-out points around the rim, giving flexibility in routing cables from different directions while maintaining IP20 ingress protection once the unused knock-outs remain sealed.

Designed for intermediate junction points in lighting circuits, downlight installations, and power distribution where circuits need to be split or extended, the junction box suits ceiling voids, wall chases, and under-floor wiring runs. The 26mm projection keeps the unit compact enough to fit within standard cavity depths, and the white finish allows it to blend into painted surfaces or remain unobtrusive when surface-mounted in service areas.

The thermoset resin construction provides better heat resistance and long-term dimensional stability than standard thermoplastic junction boxes, making it suitable for circuits running closer to their rated capacity. The four terminals accommodate loop-in, loop-out and spur connections without needing to stack multiple cables into a single terminal, which improves connection reliability and simplifies fault-finding. The box carries BS EN 60670 certification and a 25-year warranty.

Product Specification Sheet

What cable size does it accept?

The four terminals are designed for standard domestic circuit cables, typically 1.5mm² for lighting circuits and 2.5mm² for ring mains up to the 20A rating. The knock-out entry points accommodate standard PVC or LSF cable sheathing.

Is this suitable for bathroom or outdoor use?

No. The IP20 rating means the box protects against solid objects above 12.5mm but provides no protection against water ingress. It is suitable for dry indoor locations only — ceiling voids, wall cavities, and under-floor runs in habitable rooms.

How many cables can each terminal take?

Each terminal accommodates one or two cables depending on conductor size and the specific terminal design. For installations requiring multiple cables into a single terminal point, check the datasheet for exact conductor capacity or consider using a larger terminal count junction box.

What's the difference between thermoset and thermoplastic?

Thermoset resin remains stable under heat and does not soften or deform when warmed by circuit load, whereas thermoplastic housings can soften at sustained high temperatures. This makes thermoset junction boxes more suitable for circuits running closer to their rated current capacity.