February 7, 1996
Mr. John C. (Jack) Schuldt, Sr.
President, Safety Specialties Incorporated
508 Carpenter Road
Defiance, Ohio 43512
Dear Mr. Schuldt:
This is in response to your April 30, 1995 letter requesting interpretation of the electrical standard, 29 CFR Subpart S. Your letter, which was addressed to Mr. Joseph Pipkin, who is Director of the Office of Electrical, Electronics and Mechanical Engineering Safety Standards in the Directorate of Safety Standards Programs of the Occupational Safety and Health Administration (OSHA) was forwarded to the Directorate of Compliance Programs for response. Please accept our apology for the delay in responding. Your scenario and questions, and our replies, follow.
Scenario: Workplace motor control centers have boxes with 480 volts disconnects and 110 volt control power with the same box. The 480 volt load circuits are deenergized, but the 110 volt control circuits must remain energized for the following reasons:
1. Programmable Logic Controllers shut off in some instances and there is no power back-up.
2. Control power is off on a large number of machines. This could be literally hundreds of machines.
3. Hoppers and transitions could plug up with product.
4. All fluidizing lines-would have to be purged in order to prevent plugging of the line.
5. Hot glue machines would be shutdown and the glue would set.
6. Hundreds of motors would be shutoff.
7. Eight (8) to ten (10) hours of start-up time could be required to re-load processing bins, fluidizing lines and processing transitions.
8. When the system is put back into production there is a chance of many more hazards developing that would have to be addressed.
Question 1: Paragraph 1910.333(a)(1) requires that live parts to which an employee may be exposed must be deenergized before the employee works on or near them, unless the employee can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations. Would deenergizing the 110 volt control circuit as described in the scenario above be considered infeasible as delineated in the aforementioned standard?
Reply: Deenergizing the 110 volt control circuit in the above scenario appears to be infeasible as discussed in Note 2 following paragraph 1910.333(a)(1). "Infeasibility" is considered by OSHA on a case by case, work application basis. If deenergizing the control circuit(s) is infeasible, paragraph 1910.333(c)(2) would apply to work on or near the 110 volt control circuit(s). In order for the 480 volt circuit(s) to be considered deenergized, the lockout and tagging requirements of paragraph 1910.333(b)(2) must be met.
[This document was amended on October 24, 2012 to strike information that no longer reflects current OSHA policy.]
Question 2: A motor control center does not meet Table S-1 work clearances required under paragraph 1910.303(g)(1) when working on live parts operating at 600 volts or less. Rather than move the motor control center at a cost of two million dollars, can a "safe job procedure" which is audited periodically be considered an acceptable alternative or is a variance required?
Reply: An employer who has in his or her workplace contractors or equipment, including a motor control center which are in violation of any of the requirements under paragraphs 1910.303 through 1910.308 are subject to citation based solely on applicable electrical installation requirements. The safety-related work practices under paragraphs 1910.331 through 1910.335 are predicated on compliance with the aforementioned electrical installation requirements.
Application for variances are covered under 29 CFR Part 1905. Application for variances under Paragraph 1910.11 must include a statement showing how the conditions, practices, means, methods, operations, or processes used or proposed to be used would provide employment and places of employment to employees which are as safe and healthful as those required under the standard from which a variance is sought.
Please refer to paragraph 1910.305(j)(4) which, with exceptions, requires an individual disconnecting means for each motor and its associated controller. There would be no additional need to deenergize circuits for other equipment to deenergize a motor and its controller disconnected by an individual disconnecting means which meets paragraph 1910.305(j)(4) requirements.
We appreciate your interest in occupational safety and health. If we can be of further assistance, please contact the Office of General Industry [at (202) 693-1850].
John B. Miles, Jr., Director
Directorate of Compliance Programs