EXCB3-DC3-1 Solar Combiner Box 3 In 1 Out

EXCB3-DC3-1 Isolator Type 3 In 1 Out Solar Combiner Box – Visible Isolation for Three Strings

The EXCB3-DC3-1 3 in 1 out solar combiner box from HUYU Electric is purpose-built for photovoltaic systems where manual, visible DC isolation is a requirement. Instead of circuit breakers, it uses DC isolator switches for each of the three input strings and the combined output. Each isolator provides a clear physical break in the circuit — a feature increasingly mandated by fire safety codes and insurance standards for rooftop solar installations. Combined with a Type 2 SPD (40kA Imax) and optional string fuses, this unit delivers comprehensive protection in a compact IP65 enclosure.

With CE, TUV, and CB certifications, this isolator solar combiner box is ready for global markets. The factory pre-wired design saves installation time and reduces wiring errors, making it a popular choice for professional PV installers. For solar distributors and OEMs seeking a reliable DC isolator combiner box for their product line, HUYU Electric provides factory-direct OEM/ODM with private labeling and complete documentation.

Technical Specifications – EXCB3-DC 3-1

The EXCB3-DC3-1 is the isolator-based counterpart to the breaker-type EXCB1 series. By using manual DC isolator switches instead of MCBs, it provides a visible, lockable disconnection point for each of the three input strings. This design is particularly valued in regions where fire safety regulations require a physical gap in DC circuits for safe maintenance and emergency response. The optional fuses provide overcurrent protection where needed, while the built-in SPD handles surge transients. All components come factory pre-wired, so installation is quick and straightforward.

Why Manual Isolation Matters for Three-String PV Systems

In a rooftop solar system with three separate strings — perhaps an east-west-south layout — having a dedicated solar panel combiner box with isolator for each string means you can disconnect one string at a time without shutting down the entire array. Each of the three input isolators on the EXCB3-DC3-1 operates independently. The combined output isolator provides a single point of disconnection for the whole array. The lockable handles allow maintenance personnel to apply lockout-tagout procedures, ensuring the circuit cannot be re-energized accidentally while work is underway. The integrated Type 2 surge protector protects all three strings simultaneously, and the factory pre-wired enclosure means the installer only needs to connect the string cables and the inverter feed.

OEM/ODM Supply – Isolator-Type Solar Combiner Boxes for Global Markets

Buyer’s Guide

How to Choose Between an Isolator-Type and a Breaker-Type Solar Combiner Box

Key decision points for selecting the EXCB3-DC3-1 for your PV installation.

1. Isolator vs. Breaker: What Does Your Local Code Require?

The fundamental difference: a DC isolator switch is a manual disconnect that provides a visible, lockable break in the circuit. A DC MCB (circuit breaker) provides automatic overcurrent tripping and can also serve as a disconnect. Choose the EXCB3-DC3-1 isolator-type solar combiner box when your local electrical code specifically requires a visible isolation gap, or when fire safety regulations mandate lockable manual disconnects on rooftop DC circuits.

2. Where Overcurrent Protection Comes From

In the EXCB3-DC3-1, the isolators do not provide overcurrent tripping — that function is handled by the optional 15A–32A DC fuses installed in each input channel. If you prefer resettable overcurrent protection, consider the EXCB1-DC3-1 which uses DC MCBs. Both models share the same enclosure, SPD, and certification platform.

3. Sizing for Three Parallel Strings

Each input channel is rated at 32A, suitable for typical residential crystalline silicon strings with Isc up to about 25A after the 1.25 safety factor. The combined output is also rated at 32A. Ensure that the total parallel current of all three strings does not exceed 32A at the output, or size the output cable accordingly. The 1000V DC maximum voltage must exceed the string’s open-circuit voltage at the lowest expected temperature.

4. Installation and Lockout Procedures

The lockable isolator handles on the EXCB3-DC3-1 support formal lockout-tagout (LOTO) procedures. During maintenance, turn each isolator to the OFF position and lock the handle. This provides a positive, visible assurance that the circuit is de-energized. The wall-mounted IP65 enclosure should be installed with cable glands facing downward and in a location accessible for both normal operation and emergency access.

Frequently Asked Questions

Is a solar combiner box necessary?

A solar combiner box is necessary when you have multiple parallel PV strings feeding a single inverter input, or when local electrical codes require overcurrent protection and a DC isolation point at the array level. Even for a single string, a combiner box with an integrated surge protector and manual disconnect is recommended. The EXCB3-DC3-1 provides this essential protection for up to three strings, with the added benefit of manual DC isolators that satisfy visible isolation requirements in many codes.

Does a solar combiner box increase the voltage?

No, a solar combiner box does not increase voltage. It combines multiple string inputs in parallel, which sums the currents while the voltage stays the same as a single string. For example, if you connect three strings each producing 400V and 10A into the EXCB3-DC3-1 3 in 1 out solar combiner box, the output will be approximately 400V and 30A. Voltage is only increased by connecting panels or strings in series. This is a fundamental concept in PV system design that helps avoid overloading the inverter input.

What does a combiner box do for solar panels?

A combiner box for solar panels serves as the central protection and interconnection hub between the PV array and the inverter. It consolidates the DC output of multiple solar strings, provides overcurrent protection per string (via fuses or isolators), surge protection against lightning-induced transients, and a manual disconnection point for safe maintenance. The EXCB3-DC3-1 isolator solar combiner box performs all these functions using manual DC isolator switches for a visible, lockable break. This protects both the panel wiring and the inverter while keeping the system organized, code-compliant, and easy to maintain.

What is the difference between a combiner box and a distribution box?

A solar combiner box is purpose-built for photovoltaic systems and includes DC-rated protection devices — isolators or circuit breakers, surge protectors, and often fuse holders — all designed for the high DC voltages and arc characteristics of PV circuits. A general-purpose distribution box, or junction box, simply provides cable interconnection points without these protection functions. Using a standard distribution box for solar DC circuits is unsafe and violates IEC and local electrical codes. The EXCB3-DC3-1 is a dedicated solar panel combiner box with isolator that meets IEC/EN 60947-3 and other relevant PV standards. It is specifically designed to safely handle DC arc extinguishing and provide the isolation, surge protection, and weatherproofing that PV systems require.