Re: Temporary Wiring in Construction & Power lines
1) Yes. Provided the temporary light stringer or lamp is provided with a male cord cap or the cord is of a type listed in Article 400 of the NEC as hard or extra hard usage cord. Note that a branch circuit serving temporary lighting is not permitted to serve other loads. See 29 CFR 1926.405(a)(2)(ii)(C) and 1926.403(b)(2).
2) Type NM, "romex" is permitted. Cord caps on type NM is prohibited. See 1926.403(b)(2).
3) Only where the lines are deenergized and visibly grounded or where insulating barriers are installed. Note that when this second method is utilized, grounding of the crane is required and an engineer with the utility must determine induced voltages and the specific installation. The following is a letter of interpretation from OSHA on this section discussing "insulating barriers." Note that the preferred method is the goal post type barrier.
February 8, 1994
Mr. Ivan Blood
St. Paul Five and Marine Insurance Company
500 W. Madison, Suite 2600
Chicago, Illinois 60661-2594
Dear Mr. Blood:
This is in response to your October 13 letter requesting an interpretation of an Occupational Safety and Health Administration (OSHA) standard addressing the operation of a crane in close proximity to overhead power lines. I apologize for the delay in responding to your inquiry.
With regard to what is acceptable as insulating barriers to prevent physical contact of equipment or machinery with electric distribution and transmission lines when the equipment or machinery is operating within 10 feet of the power lines, please be advised as follows: Rubber insulating equipment meeting the requirements of 29 CFR 1910.137 is normally intended as protection from "brushing" type contact for employees working on the lines. Although 1910.137 is not applicable to construction work, it may be used as a compliance guide for barriers required under the exception to 1926.550(a)(15), under certain conditions. If hard direct contact with the line is not likely, rubber insulating equipment can provide protection from brush contact with the power line. However, if direct impact with the lines is reasonably likely or expected, this equipment will not provide the necessary protection. In such cases, other types of barriers would be required, such as those listed in the National Safety Council Data Sheet No. 1-743New90 and the types of plastic guard equipment covered in ASTM F968, Specification for Electrically Insulating Plastic Guard Equipment for Protection of Workers. Although guards of a type consisting of ABS plastic, 1/8-inch thick, (approximate puncture strength 50,000 volts) are often successfully used on 15KV and 34.5KV systems, none are totally impact proof to the extent that strong direct blows would leave the air gap integrity unchanged or not cause sliding or other adverse movement along the line.
While the "goal post" type of guarding approach to overhead line safety probably provides the most durable means of withstanding barrier impact, it should be remembered that no practical barrier can absolutely prevent contact of a crane (or similar material handling device), simply because the capabilities of such heavy operating devices normally overwhelm any obstruction that may be installed.
If we can be of any further assistance please contact me or Dale Cavanaugh of my staff at (202) 219-8124.
Sincerely,
Roy F. Gurnham, P.E., J.D.
Director
Office of Construction and Maritime
Compliance Assistance
