What is a ceiling junction box?

Asked By: Blandina Lederer | Last Updated: 11th February, 2020
Category: travel budget travel
4.4/5 (33 Views . 29 Votes)
Octagon or circular boxes are used to hang a light fixture, square boxes are most often used as junction boxes, and rectangular boxes hold switches and receptacles. A covered electrical box in the ceiling or a ceiling receptacle box will require an inspection to ensure that you can use it to install a light fixture.

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Similarly, you may ask, can you put a junction box in a ceiling?

Junction boxes, with blank covers are allowed above a suspended ceiling as it is not considered a closed space. Some boxes have clamps pre-installed, if not, you need to use a RX connector in the knockout. Hard to tell from your pics if they are installed. Also, an open hole in the j-box with no wire is not acceptable.

Also, can a light fixture be used as a junction box? No, there's no way a fixture can be used as a junction box. Yes, romex can be ran in pvc. There is a wire fill calculation that should be done when running wires in conduit, however, it won't be an issue for a few lights.

Considering this, what is the purpose of a junction box?

What Junction Boxes Do. A junction box performs several essential functions: Encloses the wiring connections and protects them from physical damage. Provides a means for mounting the electrical device and securing the electrical cable(s) serving the device. Prevents accidental contact with live wires and terminals.

How do you replace a junction box on a ceiling?

How to Replace a Ceiling Electrical Box

  1. Turn off the breaker inside the main electrical panel that supplies electricity to the ceiling electrical box.
  2. Go into the attic and located the ceiling box you want to replace.
  3. Remove the box from the ceiling.
  4. Install a plastic replacement ceiling box that's rated for 50 pounds.

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Are junction boxes bad?

Overfilling a Junction Box
Cramming too many wires into a junction box is not only dangerous, but it's against the National Electrical Code. Plastic junction boxes are stamped with their approved volume; you may have to calculate the volume of a steel box on your own.

Is it OK to use junction boxes?

Never connect wires outside of electrical boxes. Junction boxes (or a J box) protect the connections from accidental damage and contain sparks and heat from a loose connection or short circuit. Where connections aren't contained in an electrical box, install a box and reconnect the wires inside it.

Can you install a junction box in the attic?

Junction Boxes in Insulated Attics
In this case, the boxes will open into the attic; occasionally they're uncovered. Since insulation is combustible, you must install face plates on all attic junction boxes to prevent contact between bare wires and insulation materials.

Do junction boxes need covers?

A: It is important to cover an electrical junction box no matter where it's located. With several wires in one box, the heat generated can be multiplied. Not only does the cover protect the wiring from accidental human contact, it also prevents the spread of a fire should the wires overheat.

How do you replace a junction box?


Follow the National Electrical Code (NEC) when replacing a junction box.
  1. Turn the main breaker off in the panel box or, if you know which circuit is in the junction box, turn off the breaker to the circuit.
  2. Remove the cover from the junction box you are replacing.
  3. Remove all of the wire nuts from all of the connections.

How many wires can be in a junction box?

Metal and other material boxs fill is based on the box size in cubic inches and the required space for each conductor size. #14 wire require 2 cubic inches each. All the grounds together count as 1 wire. In your case, 6 cables with 2 wires each plus a ground requires a box that is big enough for 13 #14 wires.

Does a junction box have to be attached to a stud?

Most electrical boxes are attached to a stud before the drywall is even installed. When you add a new box to an old wall, we always try to put it in right next to a stud for solid attachment. Specialized hardware does exist to allow putting an electrical outlet or switch absolutely anywhere without reference to a stud.

What are the rules for a box junction?

These have criss-cross yellow lines painted on the road (download 'Road markings'). You MUST NOT enter the box until your exit road or lane is clear. However, you may enter the box and wait when you want to turn right, and are only stopped from doing so by oncoming traffic, or by other vehicles waiting to turn right.

Can a handy box be used as a junction box?

Handy Box: Mounts on the surface of a wall. Can contain light switches or receptacle Ideal for areas where behind-the-wall installation is difficult or not possible. Junction Box: Wires connect only to each other, never to a switch, receptacle or fixture.

Can a junction box be behind drywall?


The National Electrical Code (NEC) dictates that no wiring splices are allowed outside of an approved enclosure. One type of approved enclosure is a junction box. Junction box covers must remain accessible; they cannot be covered with drywall or other surface material.

Where are junction boxes located?

Junction boxes are often located on walls near compressors, pumps or large pieces of equipment. In addition, junction boxes are often used on the roof of commercial buildings to provide access to circuits associated with air conditioning units and ventilation fans.

How do you install a light fixture without a junction box?

  1. Step 1 - Turn Off the Power.
  2. Step 2 - Remove the Old Light Fixture.
  3. Step 3 - Find Closest Stud.
  4. Step 4 - Cut Out Hole for Junction Box.
  5. Step 5 - Attach Junction Box to Stud.
  6. Step 6 - Insert Wiring into Junction Box.
  7. Step 7 - Wire the Light Fixture.
  8. Step 8 - Attach Light Fixture to Junction Box.

When would you use a junction box?

It sometimes includes built-in terminals for the joining of wires. A similar, usually wall mounted, container used mainly to accommodate switches, sockets and the associated connecting wiring is called a pattress. The term junction box may also be used for a larger item, such as a piece of street furniture.

Should I use metal or plastic electrical boxes?

The advantage of plastic boxes is comparatively minor even for non-metallic sheathed cable -- you can avoid making one ground connection and they sometimes cost a little less. On the other hand, plastic boxes are more vulnerable to impacts. For exposed or shop wiring, metal boxes are probably better.

Can a junction box be covered by insulation?


According to Article 314.29 of the NEC, junction boxes must be accessible "without removing any part of the building." If you consider insulation part of the building, it shouldn't cover a junction box. Even if the insulation doesn't create a fire hazard or render the box inaccessible, it does obscure its location.

How far should wire come out of box?

When electrical cables route from box to box, you must leave at least six inches of free conductor wiring in the junction box for connection purposes.

How do you remove a ceiling junction box below?

Predrill the holes in the box so you do not break the box with the screws. You can remove that box from below. Easiest is to breaker it up, then pry the "J" bracket off the side of the ceiling joist. Than you can use a fan Smart Box screwed into the side of the joist.