Crowded conduit

What to try

1. 1Start on One circuit, then press + under Circuits and watch the cut for crowding change.
2. 2Pick Five circuits. The middle wires climb past 90°C. Set Wire to 10 AWG or Pipes to Two and compare.
3. 3Pick Four in a hot attic, then set Where to Room and compare.

NEC 2026 sections it covers

310.15(C)(1)

More current-carrying wires in one pipe cut what each may carry.

310.15(E)(1)

The neutral counts when it carries current.

310.15(F)

The ground does not count.

310.15(B)(1)

Hot surroundings cut what each wire may carry.

310.15(B)(2)

Pipes in sun just above a roof get a temperature adder.

Table 310.16

THHN starts from the 90°C column.

310.15(A)

Terminals rated 75°C hold it to the 75°C column.

110.14(C)(1)

Terminal ratings limit which column you use.

240.4

The wire must be good for its breaker.

240.4(B)

A circuit that feeds several receptacles gets no next size up.

240.4(D)

12 AWG copper gets a 20 A breaker at most.

250.118(A)

EMT is itself a ground. The green wire is trade practice.

250.122(E)

One green wire serves the whole pipe.

300.5(B)

Each circuit's wires stay together in one pipe.

250.122(D)

The ground stays 12 AWG when the hots go up to 10 AWG.

200.6(B)

Neutrals are grouped with their hots in each box.

210.20(A)

Loads running 3 hours or more are held to 80% of the breaker.

Section numbers only. Read the full text in your code book. Temperatures and times in the visual are teaching models.

See something wrong? Tell us and we will check it against the code.