Quoting for a distribution box might sound like a straightforward task, but it can become quite challenging, especially for newcomers. Distribution boxes come in numerous varieties, often requiring customization depending on specific needs. This makes them somewhat non-standard within the broader category of standard cabinets. So, what should we keep in mind when dealing with these cabinets?
First off, the material of the distribution box is crucial. Whether it's wall-mounted, recessed, hanging, or floor-standing, and whether it’s designed for special purposes like outdoor use, fire safety, or mining applications, the design drawings will usually provide instructions. Understanding these details helps us identify the purpose of the box and simplifies the process of estimating its size. The dimensions of the distribution box depend on the sizes of the electrical components, safety distances, and wiring requirements.
Let’s consider a standard control box as an example: it features a main switch CM1-100 molded case controlling four branch switches CM1-63 molded cases, with each circuit having an additional AC heater.
This control box includes one 100A molded case, four 63A molded cases, four AC heaters, four thermal relays (without bases), along with several signaling buttons, fuses, terminal blocks, and grounding connections. Essentially, it’s all pretty standard.
The arrangement of components typically follows this order: the main switch CM1-100 molded case at the top, with line positions reserved. Below that are four CM1-63 molded cases, also with line positions reserved. Underneath those are the four AC heaters and four thermal relays (without bases). A space of around 100mm is left between the AC heaters and thermal relays, and if there are no bases, the spacing increases to 250mm. The bottom outlet position is set at 150mm from the base (200mm if the outlets are located below the ground).
To determine the height of the distribution box:
150mm for line positions + 150mm for the main switch + 150mm for wiring positions + 135mm for outlet lines + 100mm for wiring positions + 150mm for AC and thermal relays + 150mm for outlet positions = 985mm.
For the width, we calculate based on the widest point, which involves four 63-shaped molded cases. The terminals are placed in the space on the left side of the overall empty area. The distance between the four molded cases is 81.5mm * 4 + 10mm * 4. We also estimate the distance between the bottom plate and the side walls of the distribution box at 50mm on each side:
326mm for the outlet switch width + 40mm for open clearance + 100mm for clearance on both sides = 466mm.
The depth is primarily determined by the main switch (AC might be slightly taller). It’s approximately 78mm for the main switch + 30mm for the baseplate + 100mm for the panel signal lamp and wiring distance:
78mm + 30mm + 100mm = 208mm or 200mm.
Based on the above estimations (ignoring the position of the zero-ground row), the distribution box size is approximately 1000mm high, 500mm wide, and 200mm deep. Thus, we arrive at the final dimensions of the distribution box.
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