PLC panel standards

JesperMP said:

Regarding the placement of VFDs.
VFDs generate heat and are also heat sensitive themselves. They may be rated to be able to sustain a high temperature, but that doesnt mean that you can operate them 100% at the highest rated temperature. Any VFD will be derated if it isnt operated at the 'nominal' temperature, typically 40°C.
Because of that, it makes sense to place VFDs at the bottom. If there are temperature sensitive components in the same enclosure it may be necessary with additional circulation or even cooling. If possible, place VFDs and PLCs in separate panel compartments.
Another thing is that it is the most convenient to terminate the motor cable directly at the VFD. Usually the cable screen can be terminated on the VFD chassis. That also speaks for placing the VFD at the bottom.

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Itrim said:

What do you think about using modules like this instead terminals on the very bottom of the panel?

This saves space and time necessary to wire something twice(from cable to terminals and from terminals to PLC), its easy to replace and modify. + and - distribution modules can be added as busbar on the side.

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Itrim said:

What do you think about using modules like this instead terminals on the very bottom of the panel?

This saves space and time necessary to wire something twice(from cable to terminals and from terminals to PLC), its easy to replace and modify. + and - distribution modules can be added as busbar on the side.

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rson said:

you don't want to be pulling wires in from the field through the entire wire duct to land on your plc's terminals, imo.

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Rson said:

I've used similar things in the past, such as the Weidmuller slice I/O or the Murrelektronic Cube 20 with the potential blocks below them.

IMO, where the wires are coming into the panel dictates where the terminals should be. It may seem like 'wiring twice' but what it really should do is make the field wiring / installation easier.

When you have the panel in the shop, on the bench (or rack, or wherever) is the easiest time to do good, clean wiring. You don't want to be pulling wires in from the field through the entire wire duct to land on your PLC's terminals, IMO.

If you do, at a minimum you want the terminal blocks to be removable so that you can replace a module without affecting the wiring.

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Saffa said:

This is always appreciated by the installers. Seen way too many panels where there's one fused +24V terminal for the positive feed of the field I/O. Cool... expect me to land 16 wires into that do ya?

I tend to do the same for analogs for things such as level or pressure sensors which may be 2 or 3 wire. Much easier to change something in the middle of the night if you've got +24V, 0V and the analog input + and - right there. 2 wire to 3 wire, no problem.

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