Research — Underground · Precomputed (draft, unvalidated)

Duct bank: one feeder becomes four

An end view of a duct bank in the ground. Each added conduit leaves every fill ring exactly where it was, but the harness derates the whole bank with one number, and that line sinks through the feeders until the first one is over it. Pick a story to see what helps and what does not, or switch to free play and tap the dashed circles to add conduits.

Story

Free play · every number is one cell of the exported grid or tables

Conduits per row

Rows

Conduit

Cables per conduit

Cable

Clear gap between conduits

Soil resistivity, C cm/W

Burial to top of bank

Earth ambient

Encasement

Controls snap to the values the harness was run at; nothing between them is estimated. The dashed circles on the drawing add a column or a row, and show the ampacity the grid holds for that bank.

Duct bank · end view of the trench, bank and conduits

Bank ampacity vs feeder loads

Ampacity by bank shape · same cable, soil, burial and ambient

Every check at this step · the controlling row is highlighted

Rule column: the citation the data file gives for each check. None of these limits is checked against a published standard here.

How the checks read it

Every check · the problem, the change, the fix

Required values are the functions' own defaults for these cables, read from the data file: the fill limits and the grouping source have no checked citation. A row marked value is a number the function returns with no verdict. The feeder row is the exporter's own comparison against invented loads.

Precomputed results:every verdict, required value and margin on this page was computed by the real Python harness at export time and is played back from a data file. The page runs no harness logic and holds no standards tables, and it never interpolates between exported values. Not a live API call. Precomputed by the real functions design_duct_bank_layout, calculate_conduit_fill, calculate_duct_bank_ampacity, calculate_trench_dimensions and calculate_concrete_encasement in uvm-agent-harness (commit a267697), plus calculate_cable_ampacity once per cable for the reference-condition base ampacity the bank function takes as its input; the 41 related tests are internal self-consistency checks, not a standards check. This is draft, inherited code: the harness's own validation notes call it a starting inventory, the calculation services have had no expert review, and standards ingestion has not started. The grouping factors are secondary-sourced and unchecked against the standard text; the fill limits, conduit inner diameters, cable diameters and the jam band are constants in the code; the soil, ambient and depth factors are square-root forms with no source. The feeder loads and the 5 percent tight band are invented by the exporter (provenance demo logic). Treating separate banks as thermally independent is a demo assumption: the harness has no inter-bank model. Concrete volume is the whole bank envelope (conduit volume is not subtracted), the run length of 500 ft is illustrative, and the harness prints a unit cost that is unsourced and not shown. Domain maturity, quoted from the domain page: starting inventory, not a completed review. The calculation services were inherited as live code that predates the review process and have had no expert sign-off.Real functions this maps to:design_duct_bank_layout, calculate_conduit_fill, calculate_duct_bank_ampacity, calculate_trench_dimensions, calculate_concrete_encasement.Not modeled: heat flow between conduits or between banks, spacing as an input to ampacity (the function has none), encasement as an input to ampacity, a thermal-backfill model (a lower soil resistivity number is the only stand-in), cooler ground at depth, per-conduit ampacity (one number covers the whole bank), cable pulling, vault sizing, and any standards-based limit. The conduit trade size is used as the drawn diameter, the conduit wall is drawn at a fixed width so it can be seen, and the street, soil and trench art are a fixed illustrative backdrop.See also:Duct bank, hands-off walkthrough · Cable pull, vault to vault · Conduit fill