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That is the most likely place for a fire to start. It is at this place in a circuit that mechanical connections break down. Loose splices create oxidation on the wires, oxidation creates a higher resistance creating a current draw through the resistance. This heat can become high enough to melt the insulation off of the wires. The heat build up is accumulative and the current might not be enough to trip the breaker. Junction boxes used to be made of steel which contained any flames from the surrounding wood structure. Now days boxes are made of a non flammable plastic which are sealed to cut off any oxygen to a fire that may start in the junction box. This is why the code calls for any splices that are made in a wire to be made in a junction box, and the junction box has to be accessible. There are documented cases where the junction box has been buried behind sheet rock and plaster walls and a fire has started and no one noticed until the fire burned through the wall.
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What is a splice box?
A splice box is the same terminology as a junction box. The function of a junction box is to suppress the spread of fire. In an electrical system the most likely spot for a fire to start is where wires are connected together. Loose connection of joined wires will create a resistance point. Over time with the current flowing through the connection it will heat and cool. This increases the resistance. Without repairs to this situation there will come a time when this heat will reach a combustible temperature. Depending on the type of junction box, it will suppress the spread of this fire by cutting off or limiting the oxygen supply to the fire. If the wire connection splice was in an open wall, adjacent to combustible products, the fire could spread to wall studs and then combustion could overtake the whole building.
Do you need a junction box for each light fixture?
Can lights have a junction box attached to them. So yes.
How do you find a junction box?
If the system is a conduit system you usually push a fish tape down the pipe from a known location. Usually about 99% of the time the fish tape will get hung up in the junction box. This will give you a distance from a known location to start looking for the box. If it is a Romex or Loomex system your best bet is to get an electrician friend to look at the system and ask him how he would wire the circuit. This is one of the faults that DIYers tend to do, that being burying junction boxes in the walls. They don't know the fact that most fires start in junction boxes and that is why they have to be accessible.
When does code require junction box covers to be labeled?
Junction box labeling is required by Code (NEC) on boxes containing fire alarm circuits and circuits fed from emergency power panels backed up by generators. However, it is a good trade practice to always label your j-box covers with the circuit voltage and circuit numbers.
How do you size a junction box for an angle pull an a straight through pull?
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