What does a manufacturer's worksheet distinguish?
Legrand's cable fill tool requests cable type, quantity, outside diameter and weight, and distinguishes tray and cable categories. Those separate inputs explain why a count-only takeoff is incomplete. This article does not adopt a code clause, fill percentage or sizing result from that tool.
Data Center Estimating is independent and is not affiliated with Legrand. Use approved cable data and tray design. Conductor metal area is not the outside area of an insulated or multicore cable.
Sources: Legrand Cablofil: Cable Fill Calculator, visible cable input fields
Which quantity fields should reach the engineer?
Split the route where cables enter, leave or change construction. Keep the cable schedule revision and manufacturer variant beside each diameter. An average diameter can conceal a materially different group.
| Field | Evidence | Review |
|---|---|---|
| Segment | Start, end and drawing reference | Separate changing cable groups |
| Cable group | Type, construction and revision | Do not substitute conductor area |
| Count | Cables actually in that segment | Keep spare positions distinct |
| Diameter | Approved overall dimension and unit | Use actual cable variant |
| Geometry | Count times relevant area or width basis | Engineer selects the method |
| Weight | Approved mass per length and quantity | Separate from geometric fill |
How does doubling diameter change circular area?
Illustrative example. Assume circular fictional cables with outside diameters of 10 mm and 20 mm. Using area = pi x diameter squared / 4, one has approximately 78.54 square mm and the other 314.16 square mm. Ten of each group occupy approximately 785.40 and 3,141.59 square mm of summed circular cable area respectively.
The count is identical, but the second group has four times the summed area under those assumptions. These sums omit installation arrangement, required spacing and other design constraints. They are not tray dimensions, permitted fill or a recommendation to fit either group into a particular tray.
How should a changed cable schedule affect the estimate?
Flag any changed diameter, weight or route allocation even if the total count stays unchanged. Obtain the approved revised tray and support design before changing purchased quantities. Keep the quantity delta tied to its engineering source.
The estimator records quantities and open inputs; the responsible engineer selects the installation. Engineering sign-off is performed only by the registered engineer on the job.
Common questions
What else should the bid team know?
Is conductor cross-section the cable outside area?
No. Use the actual overall cable dimensions for the stated comparison.
Does equal cable count imply equal space?
No. Size and arrangement matter.
Does the circular-area example size a tray?
No. It illustrates geometry only; approved design determines sizing.
Primary sources
- Cable Fill Calculator, visible cable input fieldsLegrand Cablofil