What is a middle junction box
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What is an intermediate junction box and what is its function?
Sometimes the cable is not long enough, or when a section of it needs to be replaced due to an accident, connection is made through an intermediate junction box.
It serves merely as an intermediate wiring function; some factories prefer to use an intermediate wiring cabinet for all instruments, but we don’t have one – the cables coming from the field go straight into the safety barrier cabinet. Well, things like intermediate junction boxes have their advantages and disadvantages; having such a device means there’s an additional point of failure, although the probability of the wiring terminals failing is basically 0……
It’s not very useful to first gather together similar instrument points located near the site using a single branch cable and put them in a small box, and then use a multi-core cable to connect that box to the cabinet room. Still, it’s advisable to have such a box in each area as a backup; after all, if there are any leaks or new instruments need to be added, it’s possible to run the cables directly to the backup wiring box without having to install additional boxes. Generally, one such box can handle 8 or 12 signals. I prefer to buy products from Weidmüller
On-site instrument junction boxes can have interfaces reserved, etc.
The intermediate junction box is used to facilitate construction, and it allows for the reservation of some spare pathways, which makes it easier to carry out minor modifications in the future without having to re-run cables. If no intermediate junction box is used, the instrument cables from the field must be run directly from the field to the control room. When there are many instruments in the field, a large number of cables need to be installed, resulting in more work. By using an intermediate junction box, multiple pairs of cables can be used to transmit signals from the junction box to the control room; for example, 12*2*1.5mm cables can be used, and this is equivalent to using 12 individual 2*1.5mm cables, thus saving time during construction. Secondly, it facilitates on-site construction by reducing the amount of conduit required for wiring the instruments. If intermediate junction boxes are not used, the cables for each instrument must be connected to the instrument busbars through conduits, and mechanical openings must be made in the busbars, which is troublesome and complicates the wiring process on site. By using intermediate junction boxes, these boxes can be installed in suitable locations, making it easier to route the wires for the instruments and reducing the need for openings in the busbars, thus saving on conduit usage. Lastly, 2–3 pairs of spare wires can be reserved in each junction box, which is useful for future minor modifications.
By using intermediate junction boxes, construction can involve less manual labor, less cable is used, the wiring looks better, and it reduces the amount of space occupied by cables in the trunking. For example, does the water supply pipe in your home lead directly from the water plant using a 6-inch pipe, or does the water plant first send the water in through larger pipes before it is distributed to various households?