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Junction Boxes

A junction box joins cables inside a closed enclosure, so the connections are covered, and IP68 types such as the JB0014 keep water out. This page includes Knightsbridge junction boxes rated from 5A to 60A for indoor circuits, IP68 gel boxes and inline connectors for outdoor and underwater joints, and an IP55 garden box that houses trailing sockets for seasonal lighting and outdoor power.

Choosing Junction Boxes

Start with where the joint will sit: in a dry void indoors, or outside where water can reach it.

Indoor junction boxes

The Knightsbridge indoor boxes, SN8400 to SN8470B, have a urea casing and are certified to BS EN 60670. Pick the current rating and terminal count for the circuit: the SN8400 is a 5A 4-terminal box, the SN8410 and SN8420 are 20A 4-terminal boxes at 59mm and 79mm, the SN8430 is a 30A 3-terminal box and the SN8460 a 20A 6-terminal box at 89mm. The SN8470B is a 60A 3-terminal box for cable up to 25mm², with built-in strain reliefs.

Outdoor and underwater joints

IP68 boxes such as the JB0014 seal the connection against water, and the JB0013, JB002 and JB004 connectors are stated for outdoor and underwater use. The JB0014 3-way and JB0015 4-way gel junction boxes are rated 24A and come with cable sleeves and a lever connector, and the JB0014 is supplied prefilled with gel. The JB0016 is an inline gel box for cable diameters of 5mm to 14mm. The JB0013 inline connector has lever terminals, while the JB002 uses screw terminals and takes H07RNF cable of 0.75mm² to 4.0mm². The JB002 and JB004 state EN 50262.

BoxRatingUse
SN8400, SN8400B5A, 4 terminals, 59mmIndoor, IP20
SN8420, SN8420B20A, 4 terminals, 79mmIndoor, IP20
SN846020A, 6 terminals, 89mmIndoor, IP20
SN8470B60A, 3 terminals, 25mm² cableIndoor, heavy duty
JB0014, JB001524A, 3-way or 4-wayOutdoor gel box, IP68
JB00416A, 3 coreOutdoor connector box, IP68
JB55BK5-channel gasketGarden box, IP55

Garden boxes and outdoor sockets

The JB55BK garden box is an IP55 and IK06 rated black polycarbonate enclosure, 334 x 220 x 116mm, with a five-channel gasket for one power input and four outputs. It takes 4G trailing sockets and wall mounts on the supplied bracket. For fixed sockets outside, see outdoor and weatherproof sockets.

Brands we stock in Junction Boxes

Knightsbridge and Penton.

Knightsbridge makes most of the junction boxes and connectors on this page.

Related categories

Secure the runs into a box with cable ties and clips, find cable in cables, and join conductors with electrical connectors. Finish the circuit with light switches.

Frequently asked questions

How do you choose a junction box?

Choose a junction box by where it will be fitted, the current and cable size of the circuit, and how many conductors need joining. Outdoor joints need a weatherproof or gel-filled box, and alarm wiring often uses a box with a lid tamper switch. The range here includes indoor mains boxes, IP68 gel boxes and security junction boxes.

When should you use a metal junction box?

A metal junction box is usually chosen where a joint needs extra mechanical protection or security, such as alarm and access control wiring in exposed or vulnerable spots. Steel boxes resist knocks and tampering better than plastic, and a metal box on mains wiring should be earthed. The range here includes mild steel security junction boxes with lid tamper switches.

What size junction box do I need?

A junction box needs enough terminals for the conductors being joined and enough space to terminate them without strain. Check the current rating and the largest cable size the terminals accept, and allow extra room for thicker or multi-core cables. The range here includes round junction boxes in several diameters and larger multi-way security boxes.

What is a junction box?

A junction box is an enclosure that protects the joints where cables are connected, keeping the terminals covered and the connections secure. Joints inside it should usually stay accessible for inspection unless a maintenance-free connector is used. Junction boxes serve lighting, power, alarm and outdoor circuits. The range here includes indoor, weatherproof and tamper-protected boxes.

  • Established 1975
  • Birmingham trade counter
  • UK-only supply

Written by the West Midlands Electrics technical team

Updated

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