Cable Tray Sizing & Routing

Quick pick (TL;DR)

Ladder tray for power (heat dissipation, support).
Perforated/solid for control & instrument.
Hot-dip galv steel outdoors; SS 316 or GRP in corrosive areas.
Size width so cables fill ≤ 40% (single layer + spacing for power).
Support every ~1.5 m.
Segregate power from instrument and keep ≥ 300 mm spacing.

Step 1 — Type & material

Choice	Use for	Notes
Ladder	Power	Heat dissipation
Perforated	Control	Small cables
Solid bottom	Instrument	Shields
HDG / SS / GRP	Outdoor / corrosive	GRP for chlorides

Step 2 — Size by fill

12 power cables, ladder tray

Given 12 cables, OD ≈ 30 mm each power → single layer + spacing Step 1 — Sum of widths Σd = 12 × 30 = 360 mm Step 2 — Fill ratio max fill 40% (power, future spare) required width = 360 / 0.80 ≈ 450 mm (0.80 = layout + spacing factor) Step 3 — Pick size next size up = 450 mm wide × 100 mm Step 4 — Support load 22 kg/m → support every 1.5 m

Power cables go single-layer for heat escape; always leave spare width.

Step 3 — Routing rules

Segregate power/control/instrument; ≥ 300 mm.
Bond trays to earth continuously.
Keep accessible; covers outdoors.

Tray width calculator

Required tray width from fill

Σ widths ÷ layout factor → required width.

Number of cables

Avg OD (mm)

Layout factor

Power cables single-layer for heat; always leave spare width.

Common mistakes

Over-filling power trays.
Mixing instrument with power.
Galv steel in coastal/chloride areas.

Requisition & datasheet

Service, type, material, location, support.
Counts, fill, width, depth, load.

Frequently asked questions

What should I know about Cable Tray Sizing & Routing?

Ladder tray for power (heat dissipation, support). Perforated/solid for control & instrument. Hot-dip galv steel outdoors; SS 316 or GRP in corrosive areas. Size width so cables fill ≤ 40% (single layer + spacing for power). Support every ~1.5 m. Segregate power from instrument and keep ≥ 300 mm spacing.

Which standards or codes apply?

NEMA VE 1 / VE 2 (metal tray), IEC 61537 (cable tray systems), NEC Article 392, IEC 60364-5-52 (grouping & spacing).

Standards — NEMA VE 1/VE 2; IEC 61537; NEC 392; IEC 60364-5-52.