Two questions, two calculations
Fill measures occupied area inside the conduit. Ampacity measures allowable current under the installation’s thermal conditions. A larger pipe can solve a fill problem while leaving conductor-count adjustment unchanged.
A worked example
Take six #10 copper THHN/THWN-2 circuit conductors and one insulated #10 equipment ground in 1-inch EMT. Their total area is 0.1477 in². Against 0.864 in² of conduit area, that is 17.1% fill, within the published 0.346 in² allowance.
With six current-carrying conductors, 30°C ambient, and verified 75°C terminals, the ampacity screen is min(40 A × 0.80, 35 A) = 32 A. A 30 A noncontinuous load passes the implemented screen. Change ambient to 40°C and the adjusted result drops to 29.12 A; the same wires still fit, but the load now exceeds that capacity.
Ordinary #10 copper overcurrent protection is a separate 30 A ceiling. The 32 A ampacity number does not approve a larger breaker.
Choose a change that addresses the failure
For excessive fill, consider the next suitable conduit size and recheck. For insufficient ampacity, consider larger circuit conductors or separate complete circuits into correctly grounded and bonded raceways. Larger wires take more space, so recheck fill too.
Do not split a circuit’s conductors arbitrarily. Grouping, grounding, bonding, and any equipment-ground resizing still need their own review.
References
NEC 2023 Chapter 9 Tables 1, 4, and 5; Table 310.16; Tables 310.15(C)(1) and 310.15(B)(1)(1); 110.14(C); 240.4(D); 300.3(B). This is an example within PassPull’s supported scope, not a complete installation design.