Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Questions can be sent to email@example.com. Answers are based on the 2014 NEC.
Type SE cable support
I am trying to solve sample questions while studying to take my contractor’s exam. In Chapter 3 for wiring methods, all of the cable assembly and raceway articles are laid out in the same numbering format. This makes it easy to go from one cable assembly or raceway article to another because, once you are familiar with the numbers, there is no need to search. The section for securing and supporting is always the .30 section. Why is there no .30 section for securing and supporting Type SE cable in Article 338?
The answer to your question is in 338.10 Uses Permitted. Type SE cable is permitted for use as service entrance conductors and as branch circuits or feeders. The requirements for securing and supporting are different for each permitted use. For that reason, the uses permitted in Section 338.10 is separated in two first-level subdivisions to address all of the installation requirements, including, but not limited to, securing and supporting. Section 338.10(A) permits Type SE cable as service entrance conductors and requires it to be installed in accordance with 230.6, 230.7 and Parts II, III and IV of Article 230. Part IV of Article 230 Section 230.51(A) requires type SE cable to be supported within 1 foot of every service head, gooseneck or connection to a raceway or enclosure and at intervals not exceeding 30 inches. Section 338.10(B) permits Type SE cable as branch circuits or feeders and contains multiple installation requirements. When used as a branch circuit or feeder, Type SE cable must be supported and secured in accordance with 334.30 at intervals not exceeding 4½ feet and within 1 foot of every outlet box, junction box, cabinet or fitting. Good luck on your contractor’s exam!
Gas pipe bonding
We are getting close to a final inspection on 12 new single homes. The general contractor is demanding that we ground a natural gas manifold installed by the plumber in the attic spaces. This manifold supplies multiple flexible gas hoses to supply the gas appliances. My recollection of NEC requirements is that the gas piping cannot be used as an equipment ground or an electrode. Are we required to run a bonding conductor to the gas manifold?
No; the NEC does not require the gas manifold to be bonded. You are correct; Section 250.52(B)(1) prohibits a metal underground gas piping system from being used as a grounding electrode. The NEC requirements for bonding gas piping are located in 250.104(B) Other Metal Piping. The only time the NEC requires metal gas piping to be bonded is where it is “installed in, or is attached to, a building or structure, and it is likely to become energized.” This means the metal gas piping is attached to or supplies an appliance that also has an electrical source, such as a gas range or gas heating system. The size of the required bonding jumper is based on the circuit that could likely energize the gas piping in accordance with 250.122. For example, if the only gas appliance in the home is a forced hot air heating system, the branch circuit supplying the fan in the heater would be the branch circuit that could likely energize the metal gas piping. Assuming the circuit is protected at 20 amperes, the minimum size bonding jumper in accordance with Table 250.122 is 12 AWG copper. There are five options given in 250.104(B) for the installer to make the bonding connection. The first option is to bond the metal gas piping to the equipment grounding conductor (EGC) of the circuit that is likely to energize the gas piping. When the electrical contractor terminates the EGC in the heating system, the bonding is complete. Nothing more needs to be done. Other options provided for the bonding in 250.104(B) would include a 12 AWG bonding jumper from the gas piping to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor, or a one of the grounding electrodes used. There is no NEC requirement to bond a gas manifold in that type of system.
NEC or product standards?
Section 422.41 requires handheld hair dryers to have an immersion-detection circuit interrupter (IDCI) installed. That is not an installation requirement. Why does the NEC contain requirements on how a handheld hair dryer is manufactured? I think this is outside of the scope of the Code, and the manufacturer should decide how to build an appliance.
The purpose of the NEC in 90.2(A) is the practical safeguarding of people and property from hazards arising from the use of electricity. During the NEC revision process, sometimes the technical committees (TCs) identify a hazard with a particular product. When this occurs, the TCs may add a requirement in the NEC to address the hazard. In some cases, the product standard has been revised, and the NEC adds a requirement to reflect that change. Hair dryers may be used in older bathrooms that do not have GFCI protection. The NEC requirement mandates an IDCI on hair dryers to open both circuit conductors if immersed. This NEC requirement saves lives. As electrical codes and standards are revised to address safety concerns, in some cases, the product standards will drive the NEC, and, in others, the NEC will make changes in the product standards necessary. There are many similar NEC requirements that impact the construction of specific appliances and equipment, including portable room air conditioners, irons and vending machines.
Receptacles above baseboard heaters
I have been told that it is a Code violation to install an electric baseboard heater under a receptacle outlet. While this seems to make sense to prevent cords from being in contact with the heater, I cannot find such a rule in the NEC. Where is it?
Article 424 contains requirements for fixed electric space heating equipment, including baseboard-type heaters. General installation requirements are in 424.9. This section recognizes that baseboard heaters may come equipped with factory-installed receptacle outlets or separate listed assemblies. These receptacle outlets would be separate from the heating elements and would be part of the baseboard heater assembly. There is no specific requirement in Article 424 to prohibit installation of baseboard heaters below receptacle outlets. However, an informational note informs the Code user that listed baseboard heaters include instructions that may prohibit them from being installed under a receptacle outlet. Article 110.3(B) in the NEC requires listed equipment to be installed in accordance with any instructions included in the listing or labeling. The requirement is in the instructions for the heater, and the installer must comply with the instructions provided. See product category KLDR Baseboard Heaters in the UL White Book for more information.
Temporary branch circuits in concrete
We have been installing temporary power on new construction using Type NM cable in concrete with success for years. We were recently informed on a large project this is an NEC violation. Doesn’t Article 590 waive the basic requirements for NM cable for temporary use?
No; the inspector is correct. Article 590 modifies a few of the basic rules in Article 334 for Type NM cable. Article 590 modifies the restrictions for using NM related to building construction type and height and does not apply when NM cable is used for temporary power. Additionally, the basic support requirements found in Article 334 are relaxed, and NM cable used as temporary must be supported to protect the cable from physical damage. No specific distance between supports is required. The prohibition of NM cable in concrete, in 334.12(A)(9), is not modified in Article 590. A cable assembly that is listed for use in concrete would be permitted.
Hair dryers may be used in older bathrooms that do not have GFCI protection. The NEC requirement mandates an IDCI on hair dryers to open both circuit conductors if immersed. This NEC requirement saves lives.