Beginning in the January issue, Electrical Wholesaling has been counting down the Top 25 need-to-know revisions to the 2005 National Electrical Code, according to Code guru Mike Holt.

For some of your electrical contractor customers who wait with bated breath for each edition of the National Electrical Code, the 2005 NEC couldn't have come soon enough. But for those just getting used to the 2002 edition, it no doubt seems like yesterday that the NEC underwent massive renumbering and AFCIs became a requirement for all 125V bedroom outlets.

Reading through this analysis, you'll notice several different type faces. Blue text is a slightly reworded representation of what appears in the Code. Underlined blue text represents Code text that has either been changed or added.

A new sentence clarifies that the “carry the locked rotor current indefinitely” requirement only applies to sizing the fire pump circuit protective devices, not the circuit conductors to the fire pump motor.

(B) Supervised Connection.

1. Overcurrent Device Selection. The overcurrent protective device(s) must be selected or set to carry indefinitely the sum of the locked-rotor current of the fire pump motor(s), the pressure maintenance pump motor(s) and the full-load current of the associated fire pump accessory equipment when connected to this power supply. The requirement to carry the locked-rotor currents indefinitely does not apply to fire pump motor conductors.

The text was revised to alert Code users that the branch-circuit conductors for a fire pump motor are sized in accordance with 430.22. In addition, branch-circuit conductors must be sized to accommodate the voltage drop requirements of 695.7.

(C) Conductor Size.

1. Fire Pump Motors and Other Equipment. Conductors supplying fire pump motors and accessory equipment must be sized no less than 125 percent of the sum of the motor full-load currents as listed in Table 430.248 or 430.250, plus 100 percent of the ampere rating of the fire pumps accessory equipment.

2. Fire Pump Motors Only. Conductors supplying a single fire pump motor must be sized in accordance with the requirements of 430.22.

Author's Comment: This means the branch-circuit conductors to a single fire pump motor must have an ampere rating of not less than 125 percent of the fire pump motor full-load current (FLC) as listed in Table 430.248 or 430.250.

Question: What size conductor is required for a 25-hp, 208V 3-phase fire pump motor? (Fig. 23, above)

(a) 4 AWG (b) 3 AWG (c) 2 AWG (d) 1 AWG

Conductors sized at 125 percent of the motor's FLC in Table 430.250; FLC of 25 hp = 74.8A, Table 430.250

Conductor = 74.8A × 1.25; Conductor = 93.5A

Answer: 3 AWG at 75°C is rated 100A

Note: Fire pump motor circuit protective device size must be set to carry indefinitely the sum of the locked-rotor current of the fire pump motor. According to Table 430.151(B), the locked-rotor current of a 25-hp, 208V 3-phase motor is 404A.

In addition, branch circuit conductors for a fire pump motor must be sized to accommodate the voltage drop requirements of 695.7.

The overcurrent protective device of an emergency power system must now be selectively coordinated. This means circuit protection schemes confine the interruption to a particular area. For example, with selective coordination, if a short circuit or ground fault occurs in a branch circuit, the only protection device that will open will be the one protecting just that branch circuit. Without selective overcurrent protection coordination, the feeder circuit protection device might open, leaving the entire system without power.

Overcurrent protection devices for emergency power systems must be selectively coordinated with all supply side overcurrent protective devices.

This new rule prohibits AFCI protection of the 120V circuit that supplies power for a nonpower-limited fire alarm system.

The power source for a nonpower-limited fire alarm circuit cannot be supplied through ground fault circuit interrupters or arc-fault circuit interrupters. (Fig. 24)

Author's Comment: This GFCI/AFCI limitation only applies to the circuit that supplies a nonpower-limited fire alarm system. Smoke detectors connected to a 15A or 20A, 120V circuit must be AFCI-protected if located in the bedroom of a dwelling unit [210.12(B)] because according to NFPA 72, National Fire Alarm Code, the circuit for the smoke detectors isn't the power source of a nonpower-limited fire alarm circuit.

A new FPN alerts the Code user to a comprehensive standard that identifies what “installed in a neat and workmanlike manner” means.

Equipment and cabling must be installed in a neat and workmanlike manner.

FPN: Information describing industry practices can be found in ANSI/NECA/BICSI 568, Standard for Installing Commercial Building Telecommunications Cabling.

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