Which source distinction matters to the estimator?
Southwire's installation guide distinguishes single conductors, multiple single conductors in parallel and multiconductor cables. That distinction supports naming the actual cable construction before counting purchase length. The guide's installation calculations are not reproduced or used to design a feeder here.
Data Center Estimating is independent and is not affiliated with Southwire. The approved electrical schedule determines conductor sizes, number of sets, neutral and grounding arrangement. The estimator must not infer these from a generic three-phase label.
Sources: Southwire: Power Cable Installation Guide, single and multiple conductor distinctions
How should separate purchase units be recorded?
Create separate lines for each cable construction and size. Keep route measurement distinct from the final length per piece, including only explicitly approved end allowances. Conductor-foot equivalents may be useful for an internal analysis, but must not replace the supplier's purchase unit for an assembled cable.
| Approved fictional arrangement | Length per piece | Pieces | Purchase length |
|---|---|---|---|
| Three separate single-conductor pieces | 50 ft | 3 | 150 ft of the specified single-conductor cable |
| One assembled three-conductor cable | 50 ft | 1 | 50 ft of the specified assembled cable |
| Two sets of three separate pieces | 50 ft | 6 | 300 ft of the specified single-conductor cable |
| Separate approved grounding conductor | 50 ft | 1 | 50 ft on its own construction and size line |
Why can two different quantities both contain 150 conductor-feet?
Illustrative example. The first two rows above contain three 50-foot conductors, but one is purchased as three separate lengths and the other as one 50-foot assembly. A supplier quote for 50 feet of the assembled product cannot be multiplied by three without changing the purchase basis.
The table uses invented complete piece lengths with no added waste, vertical rise or termination allowance. It does not assert that either arrangement is electrically interchangeable or adequate for a real feeder. It demonstrates the unit reconciliation only.
What should be checked before the quote is loaded?
Confirm the approved arrangement, assembly description, number of sets, length basis and supplier unit. Separate unlike sizes instead of blending them into one cable total. Trace grounding and neutral lines to the actual design so they are neither silently omitted nor counted twice.
Compare the extended purchase lengths with the cable schedule and takeoff ledger, then retain the source revision and open questions. Procurement packaging and reel allocation are subsequent checks. Engineering sign-off is performed only by the registered engineer on the job.
Common questions
What else should the bid team know?
Should multiconductor cable length be multiplied by its core count?
Not when the purchase unit is the assembled cable length.
Does three-phase specify every conductor needed?
No. Use the approved design and schedule.
Does the example include waste?
No. Any approved allowances must be separately identified.