Blue Sea Systems ST CLB Circuit Breaker Block, 32V DC, Surface Mount, Tin-Plated Copper Busses

Overview

The Blue Sea Systems ST CLB is a circuit breaker block for compact resettable DC branch circuit protection on boats. It is made for CLB resettable circuit breakers and uses quick connect clips so breakers snap into place without the bulk and cost of larger panel breakers.

This block family covers 6 or 12 circuit layouts, with versions available with or without an integrated negative bus. All versions are rated for 32V DC maximum, with 32A maximum per circuit, making them suitable for typical 12V and 24V DC distribution work when the installation is properly sized and protected.

The clear insulating cover has square label recesses and satisfies ABYC and USCG insulation requirements. It is a practical fit for helm panels, cabin distribution upgrades, small DC subpanels, and protected equipment spaces where the block can stay dry and accessible.

Key features

• Accepts snap-in CLB resettable circuit breakers for branch circuit protection that can be reset after a trip.
• Available in 6-position and 12-position layouts to match smaller DC panels or larger accessory groups.
• Versions with a negative bus use #10-32 positive and negative bus studs and support up to 100A per block with 32A maximum per circuit.
• Versions without a negative bus use independent source wiring and support 32A per circuit or 40A per jumped circuit group.
• Tin-plated copper busses and screw terminals support clean, low-resistance connections in a protected marine electrical space.
• Clear clip-on insulating cover satisfies ABYC and USCG insulation requirements and keeps circuit labels visible.
• Breakouts allow wire access from two directions, which helps when routing conductors behind panels or inside tight consoles.
• Accepts ring terminals and #8-32 screw terminals with captive star lock washers for secure branch circuit connections.
• Mounts with #8 screws, M4 screws, or #8 nuts for straightforward surface mounting.

Variants

This ST CLB circuit breaker block is offered in four configurations based on the number of positions and whether the block includes a negative bus.

The 6-position versions share a 5.63in mounting center and 6.69in height, while the 12-position versions use a 10.13in mounting center and 11.19in height. Blocks with a negative bus are common-source versions with positive and negative bus studs; blocks without a negative bus are independent-source versions.

• 5051: 12 positions, no negative bus. This version is the 12-circuit independent-source block, suited to installations where each circuit feed is handled separately or arranged with jumpers as needed.
• 5050: 6 positions, no negative bus. This version is the smaller independent-source block for compact DC panels, helm accessory groups, or limited-space refits.
• 5054: 12 positions, with negative bus. This version combines 12 circuit positions with integrated positive and negative bus studs for a more organized common-source DC distribution layout.
• 5052: 6 positions, with negative bus. This version gives smaller panels the same positive and negative bus layout while keeping the shorter 6-position footprint.

Installation and setup

Install the block in a dry, protected location where the cover can be opened for breaker access and labels can be read during troubleshooting. The clip-on cover helps protect the live parts once wired, while the two-direction wire breakouts give the installer more routing options behind a panel or inside an electrical compartment.

Use appropriately sized conductors, terminals, and circuit breakers for the load on each branch circuit. The operating temperature range is -10 degrees C to 60 degrees C, so placement should avoid engine heat, standing water, and areas where service access is poor.

Compatibility and use on board

This block is for DC circuit protection using Blue Sea Systems quick-connect CLB resettable circuit breakers. It works well when replacing a small fuse block with resettable breakers or when building a new accessory distribution panel for electronics, lighting, pumps, or cabin loads within the ratings of the selected breakers and wiring.

For exposed cockpits, wet lockers, or washdown areas, the block should be installed in a protected enclosure or behind a suitable panel. Optional push button waterproof boots or dress nuts can be fitted over the cover when the installation calls for a more finished breaker interface.