In general, you do not need to strip the outer sheath of cables inside a cable tray unless specific installation requirements, such as bend radius or termination, make it necessary.

General Guidance

Cables installed in a cable tray are typically designed to be used with their outer sheath intact. The sheath provides mechanical protection, maintains the cable's listed rating, and ensures the conductors remain properly insulated and identifiable. Stripping the sheath unnecessarily can compromise the cable's integrity and may violate electrical codes, as the individual conductors are not listed for independent use .

Situations Where Sheath Stripping May Be Considered

• Bend Radius Concerns: For large multi-conductor cables, stripping the outer sheath can reduce the effective diameter of the bundle, making it easier to meet bend radius requirements when transitioning into conduit or tight spaces .
• Termination or Connection: When connecting to equipment, panels, or using ferrules, the ends of the conductors must be stripped to make electrical contact, but this is typically limited to the portion that will be terminated .
• Pulling Through Conduit: Some installers strip the sheath for a short section to facilitate pulling the conductors through a conduit, but the majority of the cable should remain sheathed to maintain protection and code compliance .

Cable Type Considerations

• SER and NM Cables: These are listed as complete cable assemblies. Stripping the sheath along the entire length is not recommended, as the individual conductors are not marked or listed for independent use . Only the portion that will be terminated or exposed in a pull box may be stripped.
• UF Cable: Designed for direct burial, the sheath should generally remain intact when routed through conduit outdoors. Stripping is not recommended for outdoor or wet-location installations .
• LV, MV, HV Power Cables: Specialized sheath-stripping tools exist for preparing these cables for terminations or joints, but this is typically done only at the ends where connections are made .

Best Practices

• Leave the sheath intact for the majority of the cable run inside the tray.
• Strip only the ends where connections or terminations are required.
• Use proper tools to avoid damaging the conductors or insulation.
• Ensure any stripped section does not violate the cable's listed rating or NEC requirements.
• Consider alternative solutions for bend radius issues, such as long-radius bends or segmented conduit entries, before stripping the sheath . In summary, stripping the outer sheath inside a cable tray is generally unnecessary and should be limited to specific sections for terminations or to address bend radius constraints. Maintaining the sheath ensures mechanical protection, code compliance, and the integrity of the cable assembly.