Mi az elágazási doboz (elektromos doboz)?
A junction box – also known as an ‘electrical box’, ‘jbox’, ‘or ‘terminal box’ – is a protective box where wires are interconnected. Junction boxes are often built into the plaster of a wall, in the ceiling, or within concrete. They are standard within most homes, buildings, and factories.
Junction boxes are found both indoors and outdoors. Waterproof junction boxes are commonly used outdoors.
Junction boxes are typically made of metal or plastic. There 4 main electrical junction box types:
Fém összekötődoboz
PVC összekötődoboz (műanyag)
ABS összekötődoboz (műanyag)
Glaszfiber összekötődoboz (gumiarmált műanyag)
In most places you find electricity, you’ll find a junction box.
What Does A Junction Box Do?
A junction box serves a variety of purposes:
It protects people from coming into contact with live wires
It protects your wires from dust and dampness
It prevents small critters (rats) from chewing on your wires
It organizes the electrical floor plan into units
It prevents fires within the junction box from spreading (when properly covered)
Röviden: junction boxes serve as a protective casing for a section of wires, similar to a feeder pillar.
They stop unwanted objects – like water, rats, and your hands – from coming into contact with live wires.
When properly covered, they stop fires that start within the junction box from spreading.
They also help simplify all the electrical wiring within a building. Each junction box in a building typically indicates a different section of wiring within the overall floor plan. Larger junction boxes can also contain whole house surge protectors.
This type of organized arrangement makes doing any kind of electrical work a whole lot easier (just like using the right set of electricians tools). An electrician’s life would be a lot harder if it weren’t for junction boxes.
Choosing The Right Junction Box
With a variety of electrical junction boxes on the market, choosing the right one can seem daunting. Whether you opt for metal or plastic, the key is to match the box to your specific requirements.
Do you need a waterproof junction box? Is it an outdoor or indoor junction box? Is it a 4 or 8 terminal junction box? The list of questions goes on.
So let’s boil the selection down. These are the four main factors you need to consider when choosing a electrical junction box:
The protection rating of the junction box
How the wires are connected within the junction box (the type and number of terminals)
The material the junction box is made from
The size and shape of the junction box
Junction Box Protection Rating
The protection rating of a junction box, as defined by the National Electrical Manufacturers Association (NEMA), is essential for ensuring your box meets North American standards for safety and durability.
The NEMA ratings outline the environmental conditions that a electrical junction box can withstand, such as whether the junction box can protect against dust, light, wind, snow, and other weather conditions.
For a weatherproof electrical junction box, you want at least NEMA Type 3 (Type 3X/3RX/3SX if you also need protection against corrosion).
A NEMA rating not only clarifies if a junction box is fit for hazardous environments or outdoor use but also its resistance level against substances like oil and coolants, ensuring long-lasting protection.
Another popular rating system is the Ingress Protection (IP) or International Protection rating system. This is commonly known as an ‘IP rating’.
The IP rating describes the degree to which a junction box provides protection against the ingress of foreign objects, dust, and moisture.
‘Ingress of foreign objects’ is just a fancy way of saying ‘what can and can’t enter into’ the junction box.
There are varying levels of protection – for example, dust or water resistant junction boxes, dust tight junction boxes, watertight junction boxes, and submersible junction boxes. The exact level of protection will depend on the IP rating.
Common IP rated junction boxes include:
IP65 junction boxes – IP rated as “dust tight” and protected against water projected from a nozzle.
IP67 junction boxes – IP rated as “dust tight” and protected powerful jets of water or against heavy seas (up to 1m depth of submersion)
IP68 junction boxes – IP rated as “dust tight” and protected against complete, continuous submersion in water (suitable for continuous submersion at depths below 1m. Manufacturer will usually give details of maximum depth and/or pressure conditions)
Lastly, you have the electrical protection of a junction box. This protection rating is generally given in amps. This rating is used to determine if a junction box can handle the maximum fault current of your intended circuit.
It’s always a good idea to overrate your electrical junction boxes rather than underrate them. This overrating acts as a safety buffer – preventing human error in rating calculations or unexpected fault conditions from causing harm.
Junction Box Terminals
A terminal is a point within the junction box where two wires are connected together. You often have multiple terminals within the same junction box, with each terminal serving as a connection point for two different wires.
Make sure to use a good insulation resistance tester if you need to measure the insulation resistance. If you need to remove the insulation from the tips of the wires, you can use a set of wire strippers to strip the insulation off before connecting the wire to the terminal.
You can think of each terminal within a junction box as a dock within a shipping port. Just as each dock at the port is intended for a different line of shipment, each terminal within a junction box is intended for a different electrical connection.
Just as a shipping port can have multiple docks, so can a junction box. The most common junction boxes are 4 or 6 terminal junction boxes. That said, the exact number of terminals will always depend on how many connections you need to make. When choosing an electrical junction box make sure that you have enough terminals for each pair of wires you wish to connect.
Wiring is run through each terminal to create an electrical junction. You can measure the voltage across the junction using a multimeter. There are a few different ways to connect wires at a terminal. The type of terminal depends on how exactly the wires are connected:
Busbar screw terminals: intended for quick installation, these terminals are
