You're right to be skeptical. While the ABYC standard may permit it under certain conditions (specifically, matching the combined circular mils to the connector rating), doing so is highly likely to violate the UL Listing of the connector itself. Here's a breakdown of why, and where to look for supporting information

Why It Likely Violates UL Listing:
UL Standards Focus on Single Conductor Termination

UL standards for wire connectors (like those found in UL 486A-486B for Wire Connectors) are primarily written and tested for

single conductors within a specific size range. The UL listing verifies that the connector meets performance criteria like pull-out strength, temperature rise, and resistance when used exactly as the manufacturer intended with one conductor of a specified size. Manufacturer Instructions are Paramount

The UL listing is contingent upon following the manufacturer's installation instructions. Those instructions always specify the acceptable wire size range and the number of conductors allowed (almost invariably one conductor). Deviating from the instructions voids the UL listing.

Unpredictable Performance

Even if the combined circular mils match the connector rating, stuffing multiple conductors into a connector designed for one can lead to unpredictable and potentially unsafe performance. Consider these factors:

Uneven Pressure

The crimping mechanism is designed to apply even pressure on a single conductor. Multiple conductors may result in uneven pressure, leading to some wires not being properly secured.

Reduced Contact Area

The contact area between the connector and each individual conductor is reduced compared to a single conductor of the same combined circular mil area. This can lead to increased resistance and heat.

Material Compatibility

The compatibility of the connector material with the different conductor stranding of multiple wires, is not considered. Corrosion and fretting could result.

Where to Look for Supporting Information and Disclaimers


UL 486A-486B (Wire Connectors)

This is the key standard. You won't find an explicit prohibition against multiple conductors, because it's inherently assumed and implied in the standard's scope and testing requirements. Look for sections related to:

Markings and Instructions

UL 486A-486B requires clear marking and instructions on the connector and its packaging. These will always specify the acceptable wire size range and the number of conductors (almost always one).

Testing Procedures

The tests outlined in the standard (pull-out, temperature rise, etc.) are conducted with single conductors of specified sizes. There are no tests to validate the performance of multiple conductors.2.

Connector Manufacturer's Documentation

This is the most definitive source.

Installation Instructions

Obtain the specific installation instructions for the Hypress connector or butt splice you're considering. These instructions will clearly state the acceptable wire size range and the number of conductors allowed (almost certainly one). You can usually find these on the manufacturer's website or by contacting their technical support.

UL Listing Information

The manufacturer's documentation should also include information about the UL listing, including the UL file number and any specific conditions of acceptability. This will reinforce that the listing is valid only when the connector is used as intended.3.

ABYC Standards (A-31)

While ABYC may permit this practice under certain conditions, it's important to note that ABYC standards are generally considered a minimum safety standard for recreational boats. Compliance with ABYC does not necessarily guarantee compliance with all applicable UL standards or other regulations. Read ABYC A-31 carefully. Look for caveats or disclaimers that acknowledge the potential conflict with UL listings. The ABYC standard might state that this practice is "accepted" within the context of recreational marine applications, but it doesn't supersede the UL listing requirements or the manufacturer's instructions.

Example Scenario

Let's say you have a Hypress connector rated for 10 AWG wire. ABYC might suggest that you could use two 16 AWG wires (whose combined circular mil area is close to that of 10 AWG) in that connector. However: The Hypress connector's installation instructions will almost certainly state that it is intended for one 10 AWG wire. The UL listing for that connector is based on testing with one 10 AWG wire. Using two 16 AWG wires violates the manufacturer's instructions and voids the UL listing.

Conclusion:

While the ABYC standard might offer some flexibility, it's crucial to prioritize safety and adhere to the UL listing requirements and the manufacturer's instructions. Installing multiple conductors in a connector designed for one is almost always a violation of the UL listing and can compromise the safety and reliability of the electrical system. Always consult the manufacturer's documentation for specific guidance. When in doubt, use a connector specifically designed and listed for multiple conductors, or use a busbar and short jumpers to get from each wire to the busbar. Flag for review