Instrument cable with intermediate junction box

I don’t remember there being one; it seems like it’s a way to save costs. Many design firms these days prefer to use this kind of design.

If this is done in this way, and the construction quality cannot be ensured, there will be many problems later on, right?

There are numerous examples of the use of intermediate junction boxes; many large projects make use of them for switching purposes. For example, when the measurement points are concentrated and the signal types are the same, or when cables of the same signal type are used, intermediate junction boxes can be employed. The signals are transmitted to the cabinet rooms via the main cables in the main cable tray, which meets the regulatory requirements; the layout on-site is clear with no safety hazards, and the cost is lower compared to using branch cables throughout.

What if the cable isn’t very long? Is it still necessary to use an intermediate junction box even for lengths of two or three hundred meters?

There are no specific requirements; you can decide based on the conditions on site. If there are only a few points that are spread out, installing junction boxes will incur additional costs. However, if there are a large number of field instruments in one area and they are concentrated there, then using a 1-to-1 wiring method will result in a significantly increased width of the cable trays; or the cable trays may need to be arranged in multiple layers. This increases both the cost of cables and the cost of the cable trays, as well as the load-bearing capacity of the process ductwork. Furthermore, there are no strict regulatory requirements regarding the use of junction boxes; it depends on the actual conditions on site. If there are a large number of primary instruments at a site and they are concentrated in one area, junction boxes can be placed between these instruments, and cables can be used to transmit the signals to the terminals of the I/O cards, thereby reducing costs ； Or, if the number of field instruments is small and scattered, a 1-to-1 wiring method is used.

The intermediate transfer box helps save cables, simplifies design, and facilitates construction when the location of the instruments changes

It is essential to properly label the field junction boxes at the initial stage; otherwise, it will be very difficult to trace the wires during subsequent maintenance