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In looking for a image to answer an Industrial electronics layout and design question, I noticed that: within the cabinets, the higher power wiring seems to be at the top of the cabinet. Simply, the thicker wires are at the top. You can see it in this, this and this example.

Have I just randomly picked three examples that show this by chance, or is there a best practice for putting higher power components at the top of control panels?

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  • \$\begingroup\$ Higher power and more heat often go hand in hand. Would you want your hottest components venting across all of the others? \$\endgroup\$ – Asmyldof Apr 30 '17 at 14:41
  • \$\begingroup\$ @Asmyldof I would have thought the opposite. The 24V PSU and motor drives might get warm /hot, but I wouldn't expect the 400V incomer to unless it's under specified. No? \$\endgroup\$ – Paul Uszak May 1 '17 at 14:59
  • \$\begingroup\$ To be honest I didn't look closely at all the pictures, one of several reasons I didn't actually write an answer. \$\endgroup\$ – Asmyldof May 1 '17 at 17:05
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As you say, the cabling goes high then travels low. The reason I understood for it was safety.

If a cable falls out under its weight because its not secured properly, its bare ends will be going to a load and unlikely to be carrying a hazardous voltage.

If the routing of power was travelling upwards, the same bare ends would be coming from a supply.

There are several by-products of this decision, such as keeping the big on-off switches at the top and so on. But safety was what I understood to be the original idea. I imagine someone took that approach and copying rippled it out over the decades to become commonplace.

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    \$\begingroup\$ It also makes it less likely someone will drop a screw driver onto the high power stuff. \$\endgroup\$ – Olin Lathrop Apr 30 '17 at 15:47
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    \$\begingroup\$ I also beleve this layout is popular since most of the time the power comes from a cealing or utility pole. It would be wastefully to route it down to the floor and then back up again. \$\endgroup\$ – MadHatter Apr 30 '17 at 16:35
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Generally when you look at circuit breakers and contactors - Line or incoming connections are on top and Load or outgoing connections are on the bottom. In my experience this drives the top down design in control cabinets. The general thought process is if you have a circuit breaker or contactor that is off - the lower part of the device should be dead. This is also a benefit if a contactor or circuit breaker fails and explodes. Typically the arc flash will travel up splattering copper and carbon on the higher voltage and amperage components. If the design were reversed then your lower voltage and more sensitive components would get splattered and arc over with copper and carbon.

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Industrial cabinet layout depends entirely on how the facility installation is to be done, and for practical purposes.

While it is common to feed power in (and out) of the top of some enclosures, it is also common to feed power from underground. Buried conduits are more expensive, but when excavating to do an installation, it is just as easy to put the electrical services below ground. That also makes for a much neater installation.

Control panel layouts are normally done so that components that may require interaction (drives, PLC's, scaling and control modules) are placed at approximately eye level. Things that are not typically accessed are placed either higher or lower. Interconnect terminal strips are typically at the bottom of the enclosures, unless there is a reason to place them elsewhere.

In summary, there is no actual code, or design rule about panel layout (aside from isolating high voltage from low voltage controls typically). Panels are built as dictated by the installation requirements.

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