In a hall with twenty cabinets there's no such thing as "just a quick look". Every bad label in every cabinet costs 30 minutes of diagnostics, which production pays for at the first alarm.
The rules below are not standards — they are practices that get paid for by the second technician in the same cabinet.
Labels must survive three years of operation
Cheap paper labels last 6–9 months in hall operations. Oil, dust, humidity, UV. At the first inspection a year later they are unreadable. Aluminum tags with engraving or polycarbonate with sublimation printing are €5–8 more expensive per cabinet and last 15+ years.
The client often says: "that cabinet goes indoors, paper is enough". Two years later it gets moved to another interior, where the climate is different. The labels fall off. Pointless diagnostics begins.
The schematic lives in the cabinet, not in the archive
A plastic sleeve glued to the inside of the cabinet door. Current schematic, one A4 printout. Replaced at every inspection. Replaced at every modification.
A thousand versions can sit in the archive. At an alarm at 4 AM, nobody opens the archive — they look at the schematic from the sleeve.
Cost: 30 seconds per intervention. Payback: every second intervention.
Cables get labeled mid-route too
Client: "The cables are labeled at the ends." Inside the cabinet yes, at the equipment yes. In the cable tray between them, no. And when someone drills cables through a wall during renovation, they only know that it's "some cable from cabinet 4".
Route labels every 5 meters cost €0.30 each. On a 200-meter run that's about €12. Cheaper than 2 hours of figuring out where that cable actually goes.
Spare components are handed over in physical form
Three copies of breakers, two spare contactors, one measurement transformer. Each one listed in the delivery note, physically packed in a labeled box attached to the inside of the door.
If spare components "get forgotten" in the company warehouse, at the first failure the part is at least 2 days away. For specific components (special breakers, custom PLC modules) it can be 6–8 weeks.
Schematics by function, not by physical layout
Classic mistake: the schematic shows exactly where everything physically sits in the cabinet. Looks pretty, but during diagnostics you need to know what is functionally related — not who is physically next to whom.
Functional schematic structure: one sheet per signal (e.g., "Thermal regulation 1"), containing everything from sensor through control to output. Another sheet per power circuit. A third per communication. At an "T1 not responding" alarm you reach for the sheet where T1 lives — without searching.
Standards vs. practice
EN 60204-1 speaks about labeling. ČSN 33 2000-x speaks about labeling. STN EN 61346 speaks about labeling. None of them addresses what happens three years later during maintenance in a two-shift operation.
The rules above don't sit above the standards. They sit beyond them. After meeting the standards, the beginning practices that decide whether a cabinet is pleasant to service or unpleasant.
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*Practices developed across hundreds of installations in halls in four countries. Several of them emerged from post-mortem analysis of a client failure we resolved — the "labels in the plastic sleeve" rule came after the first night call-out where we didn't have a schematic.*