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Requirements of Junction Boxes in Electrical Instrumentation Works

Alexa bruce

Junction boxes are boxes in which wiring connections are enclosed in a metal or plastic housing. The connections that are enclosed within the junction box are usually those of a branch circuit. These boxes give you easy access to all the wiring as all the connections are enclosed in an organized manner in one place. So, you can easily make repairs, alterations, or add new connections to the conduit. Junction boxes also protect the wirings from environmental factors such as corrosion that can damage the connections. 

The IP55 junction box is manufactured by using halogen free plastics and operates in the temperature ranges of -25ºC & +40ºC. They also have a unique incandescent wire resistance of 650ºC. but when junction boxes operate in environmentally hazardous areas it is important to meet the safety requirements and requires certification to be used in such places. For the circuits that are intrinsically safe, certified boxes Ex e can be used. For the circuits that are non-intrinsically safe, boxes certified Ex d should be used. IP66 ingress protection is a requirement for all junction boxes.

Increased Safety

The construction of junction boxes shall be 1.5mm and 316LSS. They should contain a removable 316 SS gland and bottom entry. The glands need to be drilled 6 mm thick for tapered and 3 mm parallel threads. Make sure that the plate is bolted to the box by using 316 SS bolts. A neoprene gasket is used for sealing junction boxes by using an earthling stud of 8mm. the bottom of the junction boxes shall have a passage to let out the cablings. Four holes 2 top and 2 bottom are required for boxes and should have a 10 mm hole for fixtures. A gear plate is also required to be installed within the junction box.

The type of the terminals should be tunnel type and ex e rail-mounted. Always check for blue colored wiring ducts. The doors of the box should have a neoprene seal around it and at least hinged at two points. Piano hinges are not acceptable for safety purposes and they should be made of stainless steel and must be lift-off pintle type. The restriction mechanism of junction boxes prevents it from opening any more than 1600. 

Fit latches at the top and bottom that are operated by a screwdriver. Certification is required for every IP55 junction box but along with that identification label should also be present. The label is usually made of whiteblack-white plastic in blue colors and will have a tag that states the junction box is intrinsically safe.

Explosion Proof

316 SS is used in the manufacturing of junction boxes that are explosion proof. The external mounting lugs are drilled with a 10 mm and 8mm fixing hole while. As previously stated, a stainless-steel bar is inside the box which is also a factor to make it explosion proof. 

Spare entries of 20% should be provided in case of cablings. The cables are fitted according to the types of glands. The lids mostly have cast hinges that are an integral part of the box and are made of stainless steel. IPP55 Junction boxes have lids molded in Polypropylene Base.

Requirements of Ex d Enclosures

  • IP66 is the minimum protection requirement.
  • Prevent drilling of Ex d enclosures at all costs or it can be dangerous.
  • If the enclosure gets damaged then it is better to replace them in a timely manner and always make sure that the flange surfaces are clean and remain undamaged.
  • Tighten the fixing bolts with the right amount of torque.
  • Make sure that all the glands, adapters, and plugs are safety certified.
  • After the assembly of metal flanges and box lids with a grease impregnated cloth, make sure to seal it tight and properly.

Requirements of Ex e Enclosures

  • The minimum requirement for Ex e enclosures is the same as Ex d enclosures which is IP 66.
  • The same as EX d enclosures these enclosures should also be changed once they get defected.
  • If there is no official approval from the junction box company’s electrical and instrument engineers then the contents of the IP55 junction box should not be altered in any way. But if there are instructions given by the experts then you can proceed with it without worrying about any hazards.
  • Approval of Ex e terminals is required to change the damaged terminals. 
  • And like Ex d enclosures, Ex e enclosures also require the glands, adapters, reducers, and plugs to be certified and labeled. 


From the above discussion all the requirements for junction boxes are clear. Certification and labeling are the main elements required to check whether the IP55 junction box is ready to operate in hazardous environments.  Along with that many other construction and assembly characteristics need to be checked.

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