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NEC Questions 015

By Mike Holt, based on the 2002 NEC, 1 of 2

Q1. Does the NEC required lighting fixtures in a factory to have a cover to protect against breaking bulbs?

A1. No, the NEC does not require lamp protection for this application. However, lamps used for general illumination of temporary installations must be protected from accidental contact or breakage by a suitable fixture or lampholder with a guard [527.4(F)].

Q2. Does the NEC state the number of NM cables permitted under a single staple?

A2. No. NM cable must be secured and supported in accordance with 334.30 which states that nonmetallic-sheathed cable must be secured by staples, cable ties, straps, hangers, or similar fittings designed and installed so as not to damage the cable. However, this section does not specify the maximum number of cables permitted under a single staple.

As always, the installation must be approved by the authority having jurisdiction [90.4], so basically it's up to the inspector.

Q3. I heard that the Code only permits one equipment grounding (bonding) conductor to terminate on a grounding block screw terminal. Is this true?

A3: No, the number of equipment grounding (bonding) conductors permitted to terminate on a grounding terminal is limited in accordance with the equipment manufacturers instructions [110.3(B)] posted on the label located inside the panelboard. But generally, two and sometimes three equipment grounding (bonding) conductors can be terminated to a single terminal. But be careful, only one grounded (neutral) conductor is permitted on a single terminal [408.21].

Q4. A drinking water fountain is proposed to be installed within a 1 ft of a transformer. Is there a Code rule that governs the necessary clearance between the drinking fountain and the transformer?
A4. Yes, 110.26 requires sufficient step-back working space from energized parts, measured from the enclosure front, not be less than the distances contained in Table 110.26(A)(1). Assuming this is a 480 to 208V transformer, the minimum step-back working space according to this table is 3½ ft. But the water fountain/cool can be located right next to the transformer sides as long as the transformer ventilating openings are not blocked [450.9].

Q5. Is GFCI protection required for a 15 or 20A, 125V receptacle that is used to supply power for a water cooler (water fountain)?
A5. No.
Q6. What is the maximum number of circuit breakers permitted to be installed in a panel?

A6. The maximum number of circuit breakers permitted in a panelboard is limited by the instructions posted inside the panelboard [110.3(B)]. However, the NEC specifies that not more than 42 overcurrent devices can be installed in any one cabinet [408.15].

Q7. When does the NEC require a main breaker in a load center?

A7. Each lighting and appliance branch-circuit panelboard must be protected on the supply side [408.16(A)]. The overcurrent protection can be located within the panelboard, or the panelboard's feeder overcurrent protection device could be used if its rating does not exceed the ampere rating of the panelboard [408.16(A) Ex.1].

Q8. Is there a code limitation as to the total ampere rating of all circuit breakers in a panel? Example: Could the total ampere rating of all circuit breakers in a 100A panel exceed 100A?

A8. This is not a Code issue. The sum of the ampere rating of the circuit breakers in a panelboard is irrelevant. As a matter of fact, it is very common for the total ampere rating of the branch breakers in a panelboard to far exceed the rating of the panelboard.

Q9. When is an insulating bushing required on raceway fittings?

A9. Conductors 4 AWG and larger that enter an enclosure must be protected from abrasion during and after installation by a fitting that provides a smooth, rounded insulating surface, such as an insulating bushing [400.4(F)].

Rigid nonmetallic conduit male-adapter termination fittings are sometimes considered to provide the required smooth rounded insulating surface. But check with the authority having jurisdiction.

One last thing, insulating bushings aren't required where a raceway terminates in a threaded raceway entry that provides a smooth, rounded, or flared surface for the conductors. An example would be a meter hub fitting or a Meyer's hub-type fitting [400.4(F) Ex.].

Q10. Is there anything in the NEC that states that a receptacle installed in a ceiling must be of the twist-lock type?

A10. No.

2002 NEC Practice Questions Book — 2002

Learning to use the NEC is like learning to play the game of chess. To play the game well, you'll need to study the rules, understand the subtle and complicated strategies, and then practice, practice, practice. This workbook contains over 1,600 typical NEC Code practice questions from Articles 90 through Chapter 9.

Product Code: 02PQ
Pages: 124
Price: $40.00 each

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