Dwelling feeder sizing

Size one 120/240 V dwelling feeder or service run: conductors, neutral, EGC, raceway fill, burial cover, the structure disconnect, the grounding electrode conductor and voltage drop — thirteen determinations, each with its NEC article, from the same engine the paid module runs.

Size the run

A run from the utility is not a feeder. Services are sized under Art. 230 with no overcurrent device ahead of them and a different disconnect rule, and the engine cites whichever one you pick.

The load calculation is yours. Nothing here runs 220.82 or 220 Part III — the unit of a dwelling load calculation is a whole structure, not one run, and that is the paid module's job. Give a demand load and the engine takes it to the next standard OCPD and says so.

The main-power-feeder answer decides which table sizes the conductors: Table 310.12(A), which embeds the 83 % dwelling allowance, or the ordinary Table 310.16 ampacities with your derating applied.

Every method is offered in every location, and the engine tells you which ones are prohibited there and why — EMT underground is refused with the article, not quietly dropped from the list. Ambient is accepted up to 70 °C; above that the run is refused rather than answered — see the limits below.

Burial, neutral load, separate structure, fault current

A 3-wire single-phase feeder has two current-carrying conductors — the neutral of a 3-wire circuit carrying only the unbalance is not counted.

Leave it blank and the neutral comes back provisional, flagged, sized to the floor the code requires — never silently sized as if you had given a number.

Whether two attached units are one building is a PE determination under the Art. 100 definition, and the engine says so rather than deciding it. Ticking it brings in 225.31/.32 and 250.32.

What it sizes

Thirteen determinations for one 120/240 V single-phase dwelling run, 100–400 A, copper or aluminium: the ungrounded conductors, the neutral under 220.61, the equipment grounding conductor from Table 250.122, the raceway trade size from the Chapter 9 fill tables, burial cover from Table 300.5, the wiring method against the location, the structure disconnect, the grounding electrode conductor, voltage drop, and the interrupting rating.

Both paths are real. A main power feeder is sized from Table 310.12(A), which embeds the 83 % dwelling allowance; a sub-feeder goes down Table 310.16 with your ambient and conduit-fill derating applied. A service is cited under Art. 230, not Art. 215.

What it will not tell you

One feeder or service run. The paid module takes the whole house: the distribution tree, every branch panel, the panel schedules, the riser diagram and the DXF.

120/240 V single-phase 3-wire, dwelling, 100–400 A. Three-phase, paralleled conductors and non-dwelling occupancies are outside the tables this engine loads and are refused, not approximated.

The load calculation is yours. You supply the rating or the computed demand; nothing here runs 220.82 or 220 Part III, because the unit of a dwelling load calculation is a STRUCTURE and not a run.

No riser, no one-line, no DXF. There is no geometry in a single run to draw.

No stamped report, no PDF, no saved project. The numbers are whole; the document is what the paid module is for.

Ambient temperature and conductor count are accepted only as far as the engine's own derating ladders are bounded. Past that the engine would apply its last factor to any value at all, which is unconservative, so the run is refused instead. Open finding T-LFD-1.

Wiring a whole house?

The paid module takes the whole house: the service and every feeder in one distribution tree, panel schedules, the riser diagram, the load calculation the free tool asks you to bring, and the DXF.

See the plans