Junction box

Example of a junction box:
(1) Top view with a connection made with wire nuts (2) Top view of junction box with lid (3) Side view of junction box with knockouts

Any connection made in an electrical system it should be made accessible for future service or troubleshooting but must be protected against unnecessary access or damage. This is the role that a junction box plays in an electrical system - providing a location for safe, protected connections between circuits - but may also be used to:

• To provide a location to make a transition from one wire type to another.
• To provide an intermediate point in a conduit or section of wire to make feeding wire through a conduit easier.

Characteristics

There are many different designs and sizes of junction boxes because they are used for so many different purposes.

Material

A junction box may be made of metal, plastic or fiberglass.

Size

A junction box should provide ample working space and enough room to leave excess wire for thermal expansion/contraction or in case of errors.

Weather rating

Junction boxes are produced for every weather rating.

Knockouts

Junction boxes may come with pre-fabricated openings that can be used to easily bring conduit into the box or they may require the creation of appropriately sized openings upon installation.

Security

Some junction boxes may require special tools to open them or can even be locked to prevent unnecessary access.