Splices

The conductor of a flexible cord or cable that is used as a grounded conductor must be distinguishable from other conductors. Certain cords cannot be used unless durably marked on the surface with the type of designation, size, and number of conductors and include cords, such as the following:

• SJ
• SJO
• SJT
• SJTO
• S
• SO ST
• STO

The different letters in each type of portable cord designate characteristics of the cord. The S and J letters in each of these types mean that they are Junior Service. Junior Service means that the voltage rating of the cord is 300 volts. A single O indicates an oil-resistant outer jacket. Portable cords are also rated as heavy duty, medium duty, and light duty. These designations are given based on the jacket used on the cord. SJ cable and SJO cables are considered heavy duty due to their thermoset rubber jackets. A thermoplastic jacket will have a T. The absence of a T means it has a thermoset rubber jacket.

Flexible cords can only be used in continuous lengths without splice or tap. Hard service flexible cords Number 12 or larger can be repaired if spliced so that the splice retains important components, such as the following:

• Insulation
• Outer sheath properties
• Usage characteristics of the cord being spliced

Flexible cords must be connected to devices and fittings so that there is strain relief to prevent pull from being directly transmitted to joints or terminal screws.

To learn more about Construction Electrical Safety visit our Construction Electrical Safety Online Training web page.