NEC Questions Based on the 2008 NEC

September

 

 

Here is the follow up to yesterday’s newsletter. This includes all of the answers to the questions sent yesterday so you can see how you did.

 

By Mike Holt for EC&M Magazine

 

Q1. I have a 1200A 480V panel that has a working space of 3 ½ feet. The engineer says 7 feet is required. Is he correct?

A1. Maybe. The working space, which is measured from the enclosure front, must not be less than the distances contained in Table 110.26(A)(1). If you have grounded metal parts on the other side of the working space, you would need 3 ½ ft. If you have equipment 1200A or more, over 6 ft. wide, you also must have an entrance to/egress from the working space at each end of the working space [110.26(C)(2)]. If you have double the required work space (7 ft. in this instance) a single entrance/egress is allowed, if it is located at least the required working space (3 ½ ft.) from the equipment [110.26(C)(2)(b)]. 

 

Q2. What do I do with the little bare aluminum wire in hospital grade AC cable?

A2. The internal aluminum bonding strip within the cable serves no electrical purpose once it is outside the cable, and can be cut off, but many electricians use it to secure the anti-short bushing to the cable.

 

Q3. Does a motor disconnect require a three foot working space?

A3. Equipment that may need examination, adjustment, servicing, or maintenance while energized must have sufficient working space in accordance with Table 110.26(A)(1). The phrase “while energized” is the root of many debates. So, as always, check with the AHJ to see what equipment he/she believes needs a clear working space.

 

Q4. Are GFCI receptacles required in a walk-in freezer in a kitchen? 

A4. All 15A and 20A, 125V receptacles installed in an area with a sink and permanent facilities for food preparation and cooking [Article 100], even those that don’t supply the countertop surface, must be GFCI protected [210.8(B)(2)]. Many people would say that a walk-in freezer is not part of the kitchen “area”, but it is best to check with the AHJ.

 

Q5. How do you size the ground wire for parallel circuits?

A5. When circuit conductors are run in parallel [310.4], an equipment grounding conductor must be installed with each parallel conductor set and it must be sized in accordance with Table 250.122, based on the rating of the circuit overcurrent device [250.22(F)].

 

Q6. Do we have to add GFCI receptacles in our facility each time the code changes and requires more of them?

A6. No, the NEC is an installation standard, not a maintenance standard. When existing receptacles are replaced in locations where GFCI protection is currently required, however, the replacement receptacles must be GFCI protected [406.3(D)(2)].

 

Q7. Can a panel be installed in a bathroom?

A7. Maybe. Overcurrent devices must not be located in the bathrooms of dwelling units, or guest rooms or guest suites of hotels or motels [240.24(E)]. Also, the service disconnecting means must not be located in a bathroom, even in commercial or industrial facilities [230.70(A)(2)].

 

Q8. What is the maximum height that a safety switch can be installed?

A8. Circuit breakers and fuses must be readily accessible, and they must be installed so the center of the grip of the operating handle of the fuse switch or circuit breaker, when in its highest position, isn’t more than 6 ft 7 in. above the floor or working platform, unless the installation is for [240.24(A)]:

(1) Busways, as provided in 368.17(C).

(2) Supplementary overcurrent devices [240.10].

(3) For overcurrent devices, as described in 225.40 and 230.92.

(4) Overcurrent devices located next to equipment can be mounted above 6 ft 7 in., if accessible by portable means [404.8(A) Ex 2].

 

Q9. We heard that you can't enter conduit on the sides of a handy box, can you show us where it states that in the NEC?

A9. The NEC contains no such requirement.

 

Q10. Do the conduit fill requirements apply to a raceway containing telephone wires?

A10. Yes. Where communications cables are installed in a Chapter 3 wiring method, the raceway must be installed in accordance with Chapter 3 [800.100]. The 3xx.22 sections of all the raceway articles require compliance with the values listed in Table 1, Chapter 9.

 

Q11. Our utility requires a nonfused disconnect upstream of the meter and service disconnect for certain services. Is this legal?

A11. Yes, meter disconnect switches that have a short-circuit current rating equal to or more than the available short-circuit current can be installed ahead of the service disconnecting means. A meter disconnect switch must be capable of interrupting the load served [230.82(3)].

 

Author’s Comment: Electric utilities often require a meter disconnect switch for 277/480V services to enhance safety for utility personnel when they install or remove a meter.

 

Q12. Where in the NEC does it indicate how far away from a bathtub or shower a switch needs to be? 

A12. Switches can be located next to, but not within, a bathtub, hydromassage bathtub, or shower space [404.4, 680.70, and 680.72].