Power Cords and Temporary Wiring - Electrical Safety

It doesn't fail, every time I conduct a workplace safety assessment, I find extension cords throughout facilities that are running across work areas.  I find extension cords plugged (Daisy-chaining) into other extension cords.  And a lot of times I find extension cords powering machines and/or equipment.  When I talk to the equipment operators or just randomly question employees, most don't know or understand the OSHA requirements on temporary wiring.  This is why I stress to my clients, to conduct education and training on Power Cords and electrical safety.  The following is just a basic look at one of my training sessions.

What is considered temporary wiring?

–OSHA will consider as "temporary wiring" the use of more than one extension cord (connected in series or otherwise) to a permanent outlet, or the temporary connection of more than one piece of utilization equipment to an extension cord set that is connected to a permanent receptacle outlet.

• For Sec. 1910.304(b)(3)(ii) requirements applying to temporary wiring installations that are used during construction-like activities, including certain maintenance, remodeling, or repair activities, involving buildings, structures or equipment.

• OSHA does not consider a single extension cord set connected to a permanent receptacle outlet to be a temporary wiring installation.

– In such situations, extension cords are typically used to extend the length of the power supply cord on a tool or appliance to reach a nearby receptacle outlet. In this application, OSHA considers the extension cord set to be part of the utilization equipment.

–This means that one cord is used to perform a task and then immediately removed.

OSHA regulations prohibit the following uses of flexible power and extension cords:

• as a substitute for fixed wiring*
• when run through holes in walls, ceilings, or floors
• when run through doorways or windows
• when attached to building surfaces
• when concealed by walls, ceiling, or floors

Temporary wiring installations

• Extension cords are for temporary use only
• Cords must be rated for more than the intended load
• Extension cords must be protected from damage
• Avoid using excessively long cords
• Power cords should not be left tightly coiled while in use.

This can lead to over heating and possibly a fire

Power Cord Markings

(UL)E135710-F3 SJTW 3X16AWG 60c 300V VW-1

(AWG 14) c(UL) SJTW FT2 75c 3/c 14awg (2.08mm)

(AWG 12) (UL) SRW FT2 HH 90c 3/c 12awg

Power Cord Markings:

–S: Hard Service Flexible Cord

–SJ: Junior Hard Service Flexible Cord

–T: Thermoplastic insulation

–R: Thermoset insulation (rubber or synthetic rubber)

– X: Cross-linked synthetic polymer insulation

–HH: Higher temperature (usually 90°C when dry or damp)

–W: Moisture resistant (usually 60°C when wet)

–N: Nylon jacket

–-2: High temperature and moisture resistance (90°C wet or dry)

H: High temperature (usually 75°C when dry or damp

Using Power Cords

• All power cords must be inspected before use.

–Look for external defects

• Power/Extension Cord Safety Basics:

–Inspect the cord & plug. Look for cracks or damaged insulation, loose or missing plug blades, and indications of overheating or burning, especially on the plug.

–Make sure the plug is securely attached to cable. The plug should be molded to the cord or have a clamping mechanism that fits snugly around the cord without pinching.

–Check for hot or discolored outlet wall plates. That may indicate dangerous heat buildup at the connections.

–Make sure your hands are dry before plugging or unplugging a power cord.

–Make sure the plug fits snugly into the outlet. Outlets that have loose-fitting plugs can overheat and damage the cord and the plug.

–Never force a plug into an outlet if it doesn’t fit.

–Keep slack in flexible cords to prevent tension on electrical terminals.

–Grasp the plug, not the cord, when removing a plug from an outlet.

Temporary wiring installations

Grounding Path

• The path to ground from circuits must be

–Permanent

–Continuous

–Effective

• All cords must have a separate ground conductor.
• Outlets should correctly installed with polarized wiring

Power Cord Selection

• Power cords must be of adequate size and rating for the intended load.
• Power cords must be listed and labeled for their intended use

RECOMMENDED WIRE SIZE MAXIMUM LENGTH

AWG #16 — 25 Feet

AWG #14 — 50 Feet

AWG #12 — 75 Feet

AWG #10 — 100 Feet

Extension Cord Ampere Rating