Texas Master Electrician NEC Knowledge Portion

The standard rule requires ampacity of the noncontinuous load plus 125% of the continuous load, while the exception permits ampacity equal only to the sum of the continuous plus noncontinuous load (100%) where a portion of the branch circuit is connected at both supply and load ends to separately installed pressure connections covered in 110.14(C)(2).

Per the Informational Note to 210.19, 3 percent is the maximum drop at the farthest outlet for branch circuits serving power, heating, and lighting loads, whereas 5 percent is the maximum combined drop on both feeders and branch circuits to the farthest outlet.

Per 404.6(B) flush-mounted devices must be equipped with weatherproof covers, while per 404.6(A) surface-mounted devices must be enclosed in a weatherproof enclosure or cabinet complying with 312.4.

Per 90.3, Chapters 1–4 apply generally to all electrical installations; Chapters 5–7 apply to special occupancies, special equipment, or other special conditions and may supplement or modify the general requirements, and Chapter 8 (communications systems) is not subject to Chapters 1 through 7 except where specifically referenced in Chapter 8.

Mobile homes and recreational vehicles (Articles 550/551), industrial substations, and marina shore power (Article 555) are covered, while ships, watercraft other than floating buildings, railway rolling stock, aircraft, and automotive vehicles other than mobile homes and RVs are excluded.

Per 90.9(A) and 90.9(B), metric (SI) is the system of preference and SI units appear first, with inch-pound units immediately following in parentheses based on hard conversion; 90.9(C) permits either system to be used.

Code rules are enforceable requirements, while informational notes are explanatory only — such as references to other standards or related sections — and are not enforceable as requirements.

Overload protection per 430.32 is based on the motor NAMEPLATE full-load current, while conductors (430.22), disconnects (430.110(A)), and branch-circuit short-circuit/ground-fault protection are based on the Table 430.250 FLC per 430.6(A)(1), not nameplate current.

Per 430.32, motors with a marked service factor of 1.15 or greater (or a temperature rise not over 40°C) use 125% of nameplate FLA, while other motors — such as one with a 46°C temperature rise and no SF of 1.15 or greater — use 115% of nameplate FLA.

Per Table 430.52 the time-delay fuse maximum is 175% of FLC while the inverse-time circuit breaker maximum is 250% of FLC; in both cases 430.52(C)(1) permits the next higher standard rating from 240.6(A) when the calculated value is not a standard size.

A branch circuit to a single motor is sized at 125% of that motor's FLC, whereas a feeder to multiple motors is sized at 125% of the largest motor's FLC plus 100% of all other motor FLCs (plus other loads per their applicable articles).

Per 210.18 the ratings for other than individual branch circuits are 10, 15, 20, 30, 40, and 50 amperes; the difference is in permitted loads — per 210.18 Exception No. 2 and 210.23(A)(2)/Table 210.24 footnote 2 a 10-ampere circuit shall not supply receptacle outlets (it may supply lighting outlets, dwelling-unit bathroom/laundry exhaust fans, or an individual gas fireplace unit), while 15/20/30/40/50-ampere circuits may supply receptacles and other loads per 210.23(B) through (D).

Per 210.4(B) the means to simultaneously disconnect all ungrounded conductors is required at the point where the multiwire branch circuit originates (typically the panelboard); that section does not require the motor controller itself to provide it.