Electrical Safety Precautions

Avoiding electrical hazards associated with electrical heat tracing requires protective

measures in several different areas. A designer/installer must pay attention to circuit

and equipment identification, analysis of hazards and exposure to those hazards,

warnings, listing, and labeling. The designer/installer must also consider the mechanics of establishing an electrically safe work condition.

In designing, installing, or maintaining electrical heat tracing systems, the following

actions should be considered.

Identification 

1. Clearly label the outer surface of thermal insulation (after final dressing is installed). Labels should be installed on piping, vessels, pumps and similar equipment. The label should indicate that

electrical heating conductors are installed under the insulation. At least

one label should be visible from any

location. On insulated pipe lines, labels should be installed at intervals

no greater that 10 feet (3 meters)

and on alternating sides of the pipe.

If insulation is removed or replaced,

make sure that the label is replaced.

2. Clearly label any controller used to supply and/or protect electrical heat tracing

circuits and/or products. Information on the label should contain the circuit being controlled/protected by the controller.

3. Clearly label any power supply panel and/or circuit protective device used to

supply and/or protect electrical heat tracing circuits. The label should indicate

the circuit being supplied or protected. If the protective device serves as the

circuit isolation device for lockout purposes, the label should indicate this information.

4. Clearly label any power transformers, power circuits, raceways, and cable trays

or other routing methods used for providing electric power to heat tracing. The

label should indicate that the equipment/raceway supplies heating circuits.

Analysis

1. Determine the amount of electrical energy available at the source of electrical

power used to supply electric heating circuits. (NOTE: The amount of available

energy is dependent upon the design of the circuit supplying energy.)

2. Analyze the overall electrical arc-flash and shock hazards associated with the voltage, short-circuit current available, and circuit-protective device clearing time.  Consider each point in the electrical system/facility where personnel may be exposed.

3. With engineering supervision, establish the flash protection boundary by doing

the following:

• Identify the voltage level and its associated limited/restricted/prohibited approach boundaries.  Define the

distance from any potential exposed energized electrical conductor or circuit part where the incident energy exceeds 1.2 cal/square cm.

• If available energy is less than 16 kA, establish the

flash protection boundary using the formula in NFPA

70E, Part II, Paragraph 2-1.3.3.2 or in Appendix B-

2.3.2 or B-2.3.3.

• If available energy is at least 16 kA but less than 50

kA, establish the flash protection boundary using the

formula in NFPA 70E, Appendix B-5.1 or B-5.2.

4. Clearly label the electrical equipment enclosures (front, back, and ends) to show

the approach boundaries determined in the analysis. If employee is to approach

any live part closer than the Prohibited Space shown in NFPA 70E, Part II, Table

2-1.3.4, he/she must be insulated or guarded from the live parts.

5. Clearly label the electrical equipment enclosures (front/back, ends) to show the

incident energy at 18 inches (46 cm)  and at 36 inches (91 cm) from the arcflash hazard source.

Design/Installation 

1. Provide/install only electrical heat tracing and electrical power supply or control

equipment that has been evaluated, tested, and listed by a nationally recognized

testing laboratory (NRTL).

2. Install listed electrical equipment according to any directions from the listing

agency.

3. Apply electrical heat tracing and its electrical power supply and control equipment according to the National Electrical Code®

4. Provide necessary equipment or circuit disconnecting devices (for lockout) for

each circuit or item of equipment.