Engineering notes
Cable tray and trunking
Choose tray or trunking by width, load and lids. Keep signal off power in a closed slot.
Schedules often say “steel trunking” and stop. No width, no load, no lids. Power cables take real space; leave about 30% for the next pull. A tray narrower than the fill means the ceiling opens again. BMS signal and power do not share one closed slot — that is how 0–10 V starts to tick.
Write width × height, ladder or closed. Count lids, bends, tees, reducers, hangers — not only straight metres. Name the finish when the file is damp or outdoor. Electrical materials · Signal cable