Why do the two tables need different labels?
Southwire's 2023 CableTech sheet has a nominal cross-sectional-area table and a separate closest-size comparison. Its nominal table lists 250 kcmil at 127 square millimeters, while its metric-to-closest-size table pairs 120 square millimeters with 250 kcmil. Those entries serve different purposes and do not state that 127 equals 120.
Data Center Estimating is independent and is not affiliated with Southwire. This cited catalog comparison is not an ampacity rule, an approved project substitution or a complete connector selection. No standard clause or electrical limit is inferred from it.
What should the takeoff description retain?
Keep the supplied designation with its unit system instead of replacing it with the nearest-looking numeral.
| Takeoff field | Source evidence | Comparison limit |
|---|---|---|
| Conductor designation | AWG or kcmil as specified | Not a bare number |
| Metric entry | Actual metric designation if applicable | Not automatically equal area |
| Table purpose | Nominal area or closest-size basis | Do not interchange |
| Construction | Approved material and configuration | Area alone is incomplete |
| Interfaces | Approved terminations and accessories | No assumed compatibility |
| Decision | Engineer-approved substitution record | No estimator selection |
What can go wrong when a quote is normalized?
Illustrative example. A fictional electrical estimate has 1,000 m of a specified conductor designation. A supplier proposes a metric alternative and attaches a closest-size chart. The quantity reviewer keeps 1,000 m but changes the item description to equivalent cable without recording the technical decision.
The unchanged route quantity does not resolve conductor suitability or accessory scope. Retain the original line, the proposed alternative and the responsible engineer's disposition. Price an approved substitution separately where its actual scope differs, rather than declaring equivalence from the chart.
Which conclusions stay outside estimating?
Conductor performance, installation requirements and terminal compatibility need the selected product data and responsible electrical review. A nominal-area comparison does not approve any of those matters.
Do not convert a kcmil numeral directly into a square-millimeter numeral. Engineering sign-off is performed only by the registered engineer on the job.
Common questions
What else should the bid team know?
Does closest mean identical nominal area?
No. Check what the table actually describes.
Does equal route length prove equal cable scope?
No. Material, construction and interfaces still need review.
Can this table select cable ampacity?
No. Use the approved project design and selected product evidence.