Marine Bus Bar — T2 Nickel-Plated Copper Rail, 100A–600A DC, 2–20 Positions, for Boats, RVs & Solar Systems

Undersized terminal blocks that overheat under load, corroded copper bars that increase resistance over time, and cramped distribution panels where every circuit shares a single bolt — these are the wiring problems that cost marine electricians and DIY boat builders hours of troubleshooting. This marine bus bar series is built around a T2 electrolytic copper rail with nickel plating, a flame-retardant PBT base, and a polycarbonate protective cover, giving you a distribution point that handles high continuous current without thermal runaway, corrosion, or contact degradation in saltwater environments.

Each unit is a single bus bar assembly sold individually. The current-carrying rail is T2 grade nickel-plated copper (approximately 99.9% IACS conductivity). The base is flame-retardant PBT plastic (AP66 grade on GM-EP series); the protective cover is polycarbonate (PC). Terminal screws are 304 stainless steel M4 for circuit positions and M6 stainless steel studs for main input/output connections. Variants span 2 to 20 circuit positions and current ratings from 100A to 600A DC, with single row and double row configurations. The GM-EP single/double row variants are also rated for 130A AC / 300V AC. Physical dimensions: smaller variants (2–6 position double row) measure 120 × 40 × 42.8mm (4.72" × 1.57" × 1.69"); larger variants (4–12 position single/double row) measure 180 × 40 × 42.8mm (7.09" × 1.57" × 1.69"). Mounting hole spacing: 75mm (2.95") on smaller variants, 135mm (5.31") on larger variants.

This bus bar is the right choice for a boat DC distribution panel where multiple 12V or 24V circuits — bilge pump, navigation lights, VHF radio, fish finder, and accessories — need a single organized termination point rated for continuous marine current; a RV or camper van 12V power distribution bus bar where solar charge controller output, battery bank, and multiple 12V loads need to be consolidated without a fuse block; and a solar off-grid system bus bar where high-current DC connections between battery bank, inverter, and charge controller require a low-resistance, thermally stable distribution point rated for 150A–600A continuous DC.

⚡ Compatible with: 12V, 24V, and 48V DC systems. GM-EP single/double row variants also rated for 300V AC / 130A AC. Accepts M4 ring terminals (18–10 AWG) at circuit positions and M6 ring terminals (10–4 AWG or larger) at main studs. Select your position count and current rating from the Title option above.

⚠️ Current Rating Note: Always size the bus bar at or above the total simultaneous current draw of all connected circuits — never at the exact limit. For high-current variants (250A, 600A), ensure all feed cables, fuses, and ring terminals are rated to match. Undersized wiring upstream of the bus bar is a fire hazard regardless of the bus bar’s own rating.

✅ Key Features of These Marine Bus Bars

⚡ T2 Nickel-Plated Copper Rail — The current-carrying rail is T2 electrolytic copper with approximately 99.9% IACS conductivity and a nickel plating finish that prevents oxidation and maintains low contact resistance over time — critical for a high-current marine DC bus bar in a saltwater environment where bare copper would corrode rapidly.

🔥 Flame-Retardant PBT Base — The base is molded from AP66-grade flame-retardant PBT (polybutylene terephthalate), which is self-extinguishing, high-temperature resistant, and dimensionally stable under continuous electrical load — the correct material specification for a boat wiring terminal block installed near the battery bank or engine compartment.

🛡️ Polycarbonate Protective Cover — The PC cover shields all live terminals from accidental contact, water ingress, and debris while remaining transparent for visual inspection of terminal connections without removing the cover — an important safety feature for a marine electrical distribution panel bus bar in an enclosed bilge or engine bay.

🔩 304 Stainless Steel M4 & M6 Hardware — All terminal screws (M4) and main input studs (M6) are 304 stainless steel, providing corrosion resistance in saltwater spray environments and eliminating the galvanic corrosion risk that occurs when standard zinc-plated steel screws are used in a saltwater boat DC wiring system.

📊 2–20 Positions, 100A–600A DC Range — Thirteen variants cover everything from a compact 2-position 100A DC bus bar for small boat accessories up to a 6-position 600A DC bus bar for high-current inverter and battery bank connections in large RV or off-grid solar installations — all in the same product line with consistent material quality.

🔌 Single Row & Double Row Configurations — Single row variants provide a straightforward positive or negative distribution rail. Double row variants consolidate both positive and negative terminals in one compact assembly, reducing panel space requirements for a dual-rail marine power distribution bus bar in a tight electrical panel enclosure.

📐 Technical Specifications — Marine Bus Bar (GM-EP Series)

Product Series	GM-EP (B0121 / B0123 / B0124 / B0125 / B0127 / B0128 and DC-rated variants)
Current Rail Material	T2 electrolytic copper, nickel-plated
Base Material	Flame-retardant PBT plastic (AP66 grade)
Cover Material	Polycarbonate (PC), transparent
Terminal Screws	M4 stainless steel (circuit positions)
Main Input Studs	M6 stainless steel
Washers & Spacers	T2 copper, nickel-plated
Continuous Rating — GM-EP single/double row	130A AC / 150A DC
Voltage Rating — GM-EP single/double row	300V AC / 48V DC
DC-Rated Variants	100A DC / 150A DC / 250A DC / 600A DC (see Title variant)
Position Count Options	2 / 4 / 5 / 6 / 10 / 12 / 20 positions (see Title variant)
Row Configuration	Single row or double row (see Title variant)
Dimensions — Smaller variants (2–6 pos. double row)	Overall: 120 × 40 × 42.8mm (4.72" × 1.57" × 1.69"); base: 105mm (4.13"); hole spacing: 75mm (2.95")
Dimensions — Larger variants (4–12 pos. single/double row)	Overall: 180 × 40 × 42.8mm (7.09" × 1.57" × 1.69"); base: 165mm (6.50"); hole spacing: 135mm (5.31")
Mounting Flange Height	3mm (0.12")
Base Height	20mm (0.79")
Sold As	Single bus bar per order (select position count and current rating above)

❓ Frequently Asked Questions

How do I choose the correct position count and current rating for my application?

Count the number of individual circuits you need to connect — each circuit requires one position (terminal screw). Then add up the maximum simultaneous current draw of all circuits to determine the required current rating. Select a bus bar rated at or above that total. For example, if you have 8 circuits drawing a combined maximum of 120A, a 10-position 150A DC bus bar provides adequate margin. Always size up rather than at the exact limit to allow for future circuit additions.

What is the difference between single row and double row bus bars?

A single row bus bar has one row of terminal screws along a single copper rail — used for either positive or negative distribution only. A double row bus bar has two parallel rows of terminal screws on two separate copper rails, allowing both positive and negative connections to be made on the same unit. Double row bus bars are useful when you want to consolidate both rails in a single compact assembly, reducing panel space in a tight electrical enclosure.

What material is the current-carrying rail made from?

The current-carrying rail is T2 grade electrolytic copper with a nickel plating finish. T2 copper has a conductivity of approximately 99.9% IACS, making it one of the most conductive commercially available copper grades. The nickel plating prevents surface oxidation and maintains low contact resistance at the terminal interfaces over the service life of the bus bar.

Is this bus bar suitable for saltwater marine environments?

Yes. The base is flame-retardant PBT, which is resistant to moisture, UV, and saltwater exposure. The cover is polycarbonate (PC), which is impact-resistant and UV-stable. The terminal screws are 304 stainless steel, which resists corrosion in saltwater environments. The nickel-plated T2 copper rail is also corrosion-resistant under normal marine conditions. Rinse with fresh water after prolonged saltwater exposure to extend service life.

What are the terminal screw sizes on this bus bar?

The bus bar uses two screw sizes: M4 stainless steel screws for the individual circuit terminal positions, and M6 stainless steel studs for the main input/output connection points. M4 terminals accept ring terminals for standard wire gauges (generally 18–10 AWG / 0.75–6mm²). M6 studs accept larger ring terminals for the main feed cables (generally 10–4 AWG / 6–25mm² or larger on high-current variants).

Can I use this bus bar for AC wiring as well as DC?

The GM-EP single row and double row variants (B0121, B0123, B0124, B0125, B0127, B0128) are rated for 300V AC / 130A AC as well as 48V DC / 150A DC. The dedicated DC bus bar variants (100A, 150A, 250A, 600A DC) are rated for DC applications only. For AC wiring, use only the variants explicitly rated for AC and ensure the installation complies with applicable electrical codes (ABYC, NEC, or equivalent).

What are the physical dimensions of the bus bar body?

Dimensions vary by variant:

Smaller variants (2–6 position double row, GM-EP-B0121 / B0127): Overall length 120mm (4.72"), base length 105mm (4.13"), mounting hole spacing 75mm (2.95"), total height 42.8mm (1.69"), base height 20mm (0.79"), width 40mm (1.57")
Larger variants (4–12 position single/double row, GM-EP-B0123 / B0124 / B0125 / B0128): Overall length 180mm (7.09"), base length 165mm (6.50"), mounting hole spacing 135mm (5.31"), total height 42.8mm (1.69"), base height 20mm (0.79"), width 40mm (1.57")
DC-rated variants (100A–600A): Contact us to confirm exact dimensions for the specific position count selected

How do I mount the bus bar in my panel or enclosure?

The bus bar base has two mounting flanges with hex-profile holes at each end. Use M5 or M6 bolts (stainless steel recommended for marine use) through the mounting holes to secure the base to a flat panel surface. The mounting flange is 3mm (0.12") thick and sits flush against the mounting surface. Ensure the mounting surface is non-conductive or that the bus bar base is electrically isolated from any conductive panel material.

🛒 Select your position count and current rating above, then add to cart.

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