8 rules for control panel design: from EPLAN drawing to assembly
The rules I follow when drawing electrical projects — the ones that make assembly, commissioning and troubleshooting years later easier.
A good control panel isn't just one that works. It's one that the assembler can build easily, that can be tested quickly during commissioning, and that a technician can troubleshoot in five minutes from the drawings five years later. These are the rules I follow when drawing projects in EPLAN:
1. Consistent device tagging
Give every device a function (=), location (+) and device (-) designation. A full reference like =A1+P1-K12 instead of just -K1 tells you immediately which section and which panel a device belongs to. Decide the tagging scheme at the start; changing it later is painful.
2. Use cross-references
When a relay coil is on one page and its contacts on others, EPLAN's cross-references link them. That's what ends the question "which relay does this contact belong to?".
3. Wire and terminal numbers
Number every wire and terminal and print them as a terminal diagram. On site, the terminal diagram is usually the page the assembler uses most.
4. Separate power from signals
230/400 V AC power cables shouldn't share a duct with 24 V DC signal and analog cables. Analog signals and communication lines (RS-485, Ethernet) in particular pick up noise near drive output cables.
5. Leave spare capacity
Don't fill cable ducts completely, and leave free space on DIN rails and terminals. Projects always grow during commissioning: one more sensor, one more relay, one more button.
6. Account for heat
Drives, power supplies and contactors produce heat. Estimate the total loss inside the panel and plan ventilation or fans from the start. Place drives low in the panel and keep heat-sensitive electronics away from them.
7. Protection and grounding
Size every circuit's fuse or breaker for its load current and cable cross-section. Collect PE connections on a dedicated bar and ground shielded cables through it.
8. Keep the drawing and the panel identical
Put every change made during commissioning into the drawings the same day. A panel that doesn't match its drawings is more dangerous than one with no drawings at all, because it misleads people.
EPLAN's biggest advantage is that it treats a drawing as data: the bill of materials, terminal diagrams, cable lists and labels are generated from the same project. Follow these rules and those generated outputs will be right too.