TL;DR
A cable tray or cable ladder’s load class is not a property of the product alone. It is a property of the product at a specific support span. Metosu’s independent Sucofindo tests were run at a 2,400 mm support span — so the 1,340 kg cable ladder result, the 420 kg cable tray result, and the L/250 = 9.6 mm deflection limit are valid for installations where supports sit at or below 2,400 mm apart.
Space the brackets wider than the tested span and the published class no longer describes what is on your site. Support spacing is a design decision, not an installation detail.
| The question | Where the real answer is |
|---|---|
| ”What span is the load class valid at?” | The support span stated in the test report |
| ”Can I widen the supports?” | No — not without a new rating at the new span |
| ”How much will it sag at my spacing?” | The manufacturer’s span/load/deflection table |
| ”Where do I tighten spacing?” | Near heavy loads, bends, and vibration sources |
A load rating is tied to a span
NEMA VE 1-2017 classifies cable tray and cable ladder by a span and a working load. The span is built into the class itself — a “Class 8” rating is defined at an 8 ft (2,400 mm) support span. Change the span and you are no longer testing the same thing.
Metosu had both product lines load-tested by Sucofindo — PT Superintending Company of Indonesia, an accredited Indonesian testing body, part of the IDSurvey group. Both tests were run at a 2,400 mm support span, on 14 July 2025:
- Cable ladder (SLW perforated / SLU non-perforated), report E26929/FNBPAS — damaged at 1,340 kg, 2.5× the NEMA Class 8C minimum of 534.4 kg.
- Cable tray (TRC perforated / TRU non-perforated), report E26933/FNBPAS — damaged at 420 kg, clearing the NEMA Class 8B minimum of 403 kg.
Both products were also verified against a deflection limit of L/250 — 9.6 mm at the 2,400 mm span — which is 2.5× tighter than NEMA VE 1’s own working-load deflection limit of L/100 (24 mm at the same span).
Every one of those figures carries an unstated condition: at a 2,400 mm support span. They are the real, measured behaviour of the product when supports are placed 2,400 mm apart. They are not a promise about any other spacing.
What happens as spacing widens
A loaded cable tray behaves like a beam between supports. The single largest driver of how much it sags is the distance between those supports. As the span increases, deflection does not rise gently — it rises sharply, far faster than the span itself. A modest increase in support spacing produces a disproportionate increase in sag.
So a tray that sits comfortably inside an L/250 deflection limit at 2,400 mm can exceed it well before the spacing has doubled. The load on the tray has not changed. The product has not changed. Only the span has — and the span is what the rating was tied to.
This is why a wider support spacing is not a small concession. Once supports are placed further apart than the tested span:
- The deflection limit verified in the test no longer applies.
- The damage load measured in the test no longer applies.
- The NEMA class on the datasheet no longer describes the installed system.
The product may still perform well — but it is now untested at that span, and nothing on paper supports the rating. The class has quietly stopped being valid.
The factors that set safe spacing
Support spacing is not a single number to copy from a datasheet. It is the outcome of several inputs that have to be weighed together:
- Cable load per metre. The total weight of cables the tray will carry over its life — including spare capacity and future pulls — sets the load the span has to resist. Heavier fill calls for closer supports.
- The product’s tested span. This is the ceiling. A rating verified at 2,400 mm is evidence for spacing at or below 2,400 mm, and evidence for nothing beyond it.
- The deflection limit you accept. A run specified to L/250 needs closer supports than one that will tolerate L/100. The stricter the sag limit, the tighter the spacing.
- Horizontal versus vertical runs. Horizontal runs carry the cable weight directly across the span. Vertical runs load the supports differently and have their own spacing logic — they are not interchangeable.
- Proximity to bends and fittings. Bends, tees, and reducers are discontinuities. The clean beam behaviour of a straight run does not hold across them.
- Vibration. Plant rooms, pumps, generators, and seismic exposure all add dynamic load that a static rating does not account for.
A safe spacing reconciles all of these. None of them can be ignored because the others looked comfortable.
Practical rules for the site
These rules hold regardless of project, and none of them depend on a number you have to take on trust:
- Never exceed the tested span. If the load class was verified at 2,400 mm, treat 2,400 mm as a hard maximum for support spacing — not a target. Designing right up to the tested span leaves no margin for site reality.
- Tighten spacing near heavy loads. Where cable fill is heaviest, or where the tray carries an unusual concentrated load, bring the supports closer than the run’s nominal spacing.
- Add support at bends and fittings. Place a support close to each bend, tee, and reducer rather than relying on the straight-run spacing to carry the fitting.
- Tighten spacing near vibration. In plant rooms and anywhere subject to vibration or seismic load, reduce spacing and treat the dynamic environment as a design input, not an afterthought.
- Ask the manufacturer for the span/load table. A manufacturer that has tested its products can tell you how load capacity and deflection change with span. If they cannot, the only span you can rely on is the single one in the test report.
Writing it into a BOQ and verifying on site
Support spacing is too important to leave to the installer’s judgement on the day. Put it in the specification.
In the BOQ and the specification:
- State the maximum support spacing explicitly, in millimetres — do not leave it implied by the NEMA class.
- State the deflection limit you require — L/250 or L/100 — so the spacing can be set against a known target rather than a default.
- Require that the support spacing sits at or below the tested span stated in the manufacturer’s load test report, and require that report as a submittal.
- Call out closer spacing near bends, heavy-fill sections, and vibration sources as a separate line, not a general note.
On site, verify before sign-off:
- Measure the as-installed spacing between supports against the specified maximum.
- Confirm supports are present close to bends and fittings.
- Check that no run has been stretched between supports to save on brackets — the most common way a verified rating is lost in the field.
A cable tray installed at or inside its tested span carries the rating it was sold with. One stretched beyond that span carries a class letter that no longer means anything.
Get the span data
Metosu’s Sucofindo reports — E26929/FNBPAS for the cable ladder and E26933/FNBPAS for the cable tray — state the tested span and the load and deflection results in full. For help setting support spacing for a specific run, finish, or load case, email marketing@metosu.com or contact the Metosu technical team.
Further reading
- NEMA class vs tested capacity — how to verify a real load rating
- NEMA VE 1 load classes explained — what 8A, 8B, and 8C mean
- Cable ladder vs cable tray — choosing the right system for the run
- Cable tray sizing guide — sizing for cable fill and future capacity
- Cable tray · Cable ladder · Full catalogue (PDF)
