Section 4.6.3.9 requires terminals for more than one conductor to be identified and intended for the purpose. This has always been a huge problem in the electrical industry. All too often, multiple conductors are found to be terminated to a single barrel terminal that has only been evaluated and listed for a single conductor termination. Always check the manufacturers installation instructions to see if the terminals have been evaluated for more than one conductor.

According to UL product category AALZ, product terminals, including wire connectors and terminal screws, are acceptable for connection of only one conductor, unless there is marking or a wiring diagram indicating the number of conductors which may be connected.

Below is a sample of NFPA 731. For the complete section, see the actual NFPA 731 text at NFPA.ORG. Once there, click on the free access link to the latest edition of NFPA 731.

4.6.3 Wiring.

4.6.3.9 Terminals for more than one conductor shall be identified and intended for the purpose.

4.6.3.10 Conductors under a single terminal shall be of the same gauge and composition.

4.6.3.11 Terminals shall be marked or color coded where necessary to indicate the correct connections.