Issues with the junction box

Is your junction box an on-site junction box?

I’m not sure how your drawings are designed; I’ve always been against the use of on-site junction boxes. Every additional dry contact (terminal block) introduces an element of instability, and no matter how good a terminal block may be, it cannot compare to a direct cable connection. Just decide based on the situation on site; there’s no need to necessarily go into the junction box. For on-site junction boxes, the issue of spare capacity should be taken into consideration; generally, an additional 5%-10% is provided

It’s the customer’s request; there’s nothing we can do about it.

1. May I ask if the DO terminal of the 220V solenoid valve needs to be connected to the on-site instrument junction box? The voltage level of these instruments is usually 24V; instrument technicians are accustomed to working with 24V. If there are many 220V DO points (for example, 50), it is advisable to consider installing a junction box; moreover, a separate junction box should be used to distinguish them from the 24V ones. Maintaining a 220V wiring box is rather troublesome; it needs to have high-voltage markings to prevent misunderstandings. . . It is better to choose a 24V solenoid valve. 2. Do the power wires of 4-wire instruments need to go into the junction box? No need, just pull it straight; there can’t be too many power supply points. 3. The junction box already includes spare input ports and corresponding terminals, so is it really necessary to add more terminals? All the wires of the main cable are connected to the terminals. For example, 10 pairs of main cables, with 20 terminals, and 10 holes for branch cables. A few more wealthy terminals would work too.

1. I believe that it is not advisable to install a wiring box on-site for 220V systems, as this adds an additional point of risk; some people are careless and may mistakenly use 24V instead. 2. The 2-wire and 4-wire instrument power cables go directly to the control room. 3. Several pairs of wiring terminals should be reserved, just in case.

In my opinion, whether to equip on-site instruments with junction boxes depends on the number of instruments; it’s not necessary for just one or two instruments, as having additional connectors will only lead to more faults. The junction box already includes a spare inlet and corresponding terminals, so there is no need to add more terminals...

Regarding the design, for a simple modification, one just needs to consider the costs involved. If a junction box is used, an additional box is required; in the absence of a junction box, N separate cables need to be installed, which increases both the construction costs and the cost of the cables