Computes the open (perforated) area of a cable tray as a percentage of its total plan area over a given length — a simple screening indicator used alongside cable ampacity/fill checks to gauge how freely a ventilated or perforated tray can dissipate heat compared to a fully solid-bottom tray. Ladder tray is effectively ~100% open; perforated trough tray is typically 15-40% depending on the hole pattern; solid-bottom tray is 0%.
Standards followed
Open-area ratio = open (perforated) area / (tray width × length) — a general screening metric, not a normative code table
What it can do
- Ventilation (open-area) ratio from tray width, assessed length, and total open/perforated area.
- Grading band from LOW to HIGH for a quick sense of how ventilated the tray section is.
Example problem
300mm wide tray, 10m length assessed, 1.2m² total perforated open area.
- Total tray plan area = 0.3m × 10m = 3.0m²
- Ventilation ratio = 1.2/3.0 × 100 = 40%
40% open area — GOOD ventilation band.
This is a plan-area open ratio, not a full convective heat-transfer calculation — it doesn't replace an ampacity derating study for enclosed or heavily loaded trays (see the Cable Tray Fill and Cable Ampacity calculators for capacity/fill limits).