The program should include the essential ingredients of Chapter 19 of NFPA 70B, Portable Electrical Tools and Equipment, and ANSI/UL 745 Series, UL Standard for Safety for Portable Electric Tools.. This includes employee training, maintenance, cord and attachment plug care, extension cords, major overhauls, and leakage current testing.
9.3.1 Inspection and Maintenance
Portable electric tools and equipment such as cords, plugs, and GFCIs should be inspected before use by both the issuer and the user for: signs of chaffing, cracking, wear, or other forms of faulty insulation; evidence of a faulty grounding conductor, cracked plug, or receptacle housing; bent or missing plug or connector prongs; dead front plugs, receptacle, or connectors;
a missing, bent, or otherwise abused switch; or, an improperly functioning trigger lock (dead
man's switch). While in use, tools and equipment should be observed for proper operation, including any signs of overheating or excessive sparking. Portable electric tools, equipment, and GFCIs should be inspected or trip-tested by the user each day before use. Signs of a defect shall9.21 require the return of the device for repair.
9.3.2 Conditions of Use
Portable electric tools, equipment, and GFCIs shall9.22 not be used in hazardous locations, unless marked to indicate suitability for such use.
Portable electric tools and equipment shall9.22 not be handled or suspended by their cords.
Tools and equipment shall9.22 be used only for their intended purpose, and when guards are required, such guards shall9.22 be in place and functional.
Tools and equipment shall9.22 be grounded via the case, double-insulated, specially approved low voltage types, or self-contained and battery-operated.
Tools and equipment used in damp areas should be approved for such use. Generally, electrical tools are not approved for use in wet or damp areas without other means of protection.
9.3.3 Use of Extension Cords
Use of extension cords should be minimized. Such cords shall9.23 be selected, based on intended use, such as length, gauge of conductors, waterproof connectors for wet or damp areas, and are subject to the same conditions as the tool or equipment cord. Extension cord sets shall9.23 be listed as an assembly by an NRTL (see Section 2.5). Extension cord sets used on construction sites shall9.23 contain the number of conductors necessary for the circuit, plus an EGC. The cords shall9.23 be hard use or extra-hard use as specified in the NEC. Daisy chaining of extension cord sets is prohibited by the listing requirements.
Extension cords shall9.23 be visually inspected before each use and, if damaged or worn, they shall9.23 be replaced.
Extension cord sets used at construction sites and used with portable metal electric tools and appliances shall9.24 be of three-wire type and shall9.24 be designed for hard or extra-hard usage.
Flexible cords used with temporary and portable lights shall9.24 be designed for hard or extra- hard use. Extension cords approved for outdoor use may be identified by "outdoor" or "W-A" on the jacket.
9.3.4 Double Insulated Tools
The NEC references the use of double-insulated tools in UL Standard UL 1097, Double Insulation Systems for Use in Electrical Equipment, which provides the requirements for equipment marked "Double Insulation" or "Double Insulated." Since the end product standard takes precedence, the end-product UL Standard should also be consulted when there are questions pertaining to products that require double insulation.
Double insulation is a system comprised of two insulation systems (basic and supplementary) that are physically separated and are not subjected to temperature, contaminants and other deteriorating factors at the same time.
Basic insulation is applied to live parts to provide protection against electrical shock.
Supplementary insulation is independent of the basic insulation and provides protection against electrical shock in case of failure of the basic insulation. Also of importance is the reinforced insulation that consists of one or more layers of insulating material that, in itself, provides the same degree of protection as double insulation.
For example, two layers of insulation separating an armature lamination from an armature conductor is not double insulation. This is reinforced insulation. To achieve a double insulated system, one layer of insulation separates the armature lamination from the armature conductor (basic insulation) and an insulating sleeve provides a second layer between the armature lamination and the motor shaft (supplementary insulation).
Generally, double insulated equipment is constructed such that double insulation is provided between all live parts and (1) the accessible surfaces of the equipment, and (2) all inaccessible parts and surfaces that are conductively connected to the accessible surfaces of the equipment.
Under certain conditions, reinforced insulation systems are acceptable when applied to brushcaps; brushholders; commutators, and end turns of armature winding switches; power supply cords; and, internal wiring.
Power supply cords for double-insulated tools shall9.25 be jacketed and shall9.25 not include a grounding conductor.
"Double insulated" or "double insulation" (UL 1097) are permanently marked on the tool. In addition, the double insulated symbol (a square within a square) may be used.