Junction Boxes 101: Types and Installation Explained

 Wires and cables are all around you be it your vehicle, phone or home you are essentially surrounded by them despite not being able to see them. All this wiring has a meeting point in a component called a junction box. This box is where all the live wires are.

The design of a junction box allows you to access and perform maintenance on your home's electrical components. Junction boxes are also able to protect electrical connections from the elements and someone tampering with them. However, as is the case with cables and wires, not every electrical junction box is the same, and choosing the right one is key to a safe home.

Types of Junction Boxes

source: housedigest.com

Rectangular

A rectangular or standard junction box as it's also called, is made to be used with single-conductor connections as well as the base for regular power point connections. These j boxes for electrical fittings come with depths between 4 cm and 9 cm. You can link two or more boxes to a rectangular junction box thanks to its detachable sides.

Round Pan

With round-pan electrical junction boxes, you get to accommodate up to three wires but only for plain ceilings and in areas with minimum wall lighting. That's because of the shallow depth range that stays anywhere between 1.3 cm and 2 cm. 

Square

Standard square junction boxes make sense in applications where different conductors go in different directions since the design of this box gives extra space for multiple connection points. This translates into a depth range between 3 cm and 5.5 cm with usually there being about 10 cm on each side of the box. 

Octagon

An octagon or standard round junction box is mostly used when you want to fix lamps on a wall or install lights on a ceiling. The depth of an octagon box can be as shallow as 4 cm and as deep as 7.5 cm but the thickness and width can be different depending on the use case scenario.

Ceiling Fan

Quite self-explanatory, ceiling fan boxes are made to house electrical fittings of ceiling fans which means they have a tight ceiling fixing in order to provide support for the fan's rotating load.

Outdoor

As you would expect, an outdoor electrical junction box is used on outside walls or the surface of roof decks as its construction allows it to survive the rigours of the elements. It's the steel, aluminium or high-impact PVC material that makes an outdoor box so durable.

What Matters in a Junction Box

Material

As you already know you can either make use of a metal or plastic junction box. Plastic j boxes for electrical fittings are more common than they used to be since they are rust-free, non-conductive and more affordable than their heavier counterparts. Metal junction boxes, on the other hand, are more impact-resistant and also better for the environment. 

Size

The dimensions of a junction box affect its versatility and compactness at the same time. The larger the box the more wiring it can accommodate but also the more space it takes up. Smaller boxes are more concealing and easier to install since they don't take up as much space.

Terminals

Depending on the amount of wiring, you should take into consideration the number of terminals an electrical junction box will have. The more the merrier but know that this increases its price as well as its size.

Protection Rating

This is important, especially for outdoor electrical junction boxes as an IP rating refers to the box's ability to keep dust and water from entering the enclosure it creates. The material is not the only factor here, seals around the box are key too.

Installing a Junction Box

1. The first step is to mount the junction box but you need to detach the wires from each other first and make them hang loose. You should also use an anchor to secure the box alongside with screws in order to keep it in place for a long time.

2. Next comes the use of cable clamps. In order to prevent the cables from getting tangled, place a clamp on each one. These clamps usually come with the junction box and you're supposed to pass them through a knockout hole into the box.

3. After you've clamped the cables, it's time to secure them. Make sure that when doing this you keep about half a centimetre between each clamp and the box and that the conducting wires have about 1 cm of clearance from the box. Then just tighten the screws to secure the wires in place and move on.

4. When you've secured the cables, you then need to join the wires which is done by following manufacturer-provided guidelines. Connectors are also used in this case as the wires are combined together according to their colour.

5. Once all of the above is done, fold the wires so they don't open up the box and turn on the circuit breaker to test them. Once tested close the electrical box and you're done.