EXCB1-DC3-1 Solar Combiner Box 3 In 1 Out

EXCB1-DC3-1 Solar Combiner Box with Three Inputs and One Output Including MCB’s for Up to 3 Single-String Models

The HUYU Electric EXCB1-DC3-1 Solar Combiner Box is designed for residential or light commercial photovoltaic systems with up to 3-parallel strings. This product will take 3 DC inputs from solar panels and provide 1 DC output with the use of an MCB protecting each of the 3 inputs. This breaker provides reliable protection against over-currents and short-circuiting while allowing the user to manually isolate power from the unit for maintenance purposes. It comes in a wet-rated IP65 enclosure and contains a Type 2 SPD (40kA Imax) and the optional use of DC fuses which will create a one-unit protection hub.

This 3-string solar combiner is CE, TUV, and CB certified and meets both US & International safety standards. Since the interior of the unit is already wired up for you, installation is fast and simple because all you have to do is land the string cables and inverter lead at the connectors provided. HUYU Electric provides direct-to-distributor/installer factory OEM/ODM with private-labeling and complete documentation for solar distributors/installer looking for an easy-to-install, code-compliant breaker type solar combiner.

Technical specifications of EXCB1/3-DC 3-1

OEM/ODM Supply – Brand-Ready 3-String Solar Combiner Boxes

Buyer’s Guide

How to Select a Solar Combiner Box for Multiple Strings

Key factors for choosing the EXCB1-DC3-1 for your residential or small commercial PV system.

1. Determining the Number of Inputs You Need

Count the parallel strings in your PV array. If you have three independent series strings that will feed one inverter MPPT, a 3 in 1 out solar combiner box like the EXCB1-DC3-1 is the exact fit. Using a box with fewer inputs would force you to wire strings together before the combiner, losing individual overcurrent protection. A box with more inputs can be used, leaving spare channels for future expansion.

2. Breaker-Type vs. Isolator-Type Combiner Boxes

The EXCB1 series (including the DC3-1) uses DC MCBs that trip automatically on overcurrent. This is convenient for residential systems where a temporary overload might occur and a quick reset is preferred. If your local electrical code requires a visible isolation gap or lockable manual disconnect, consider the EXCB3 series which uses DC isolator switches instead. Both series include identical SPD and fuse options.

3. Current and Voltage Ratings

Verify that each string’s short-circuit current (Isc), multiplied by the safety factor 1.25, stays below 32A. The maximum DC voltage rating of 1000V must exceed the string’s open-circuit voltage (Voc) at the lowest expected ambient temperature. For most 60-cell and 72-cell modules, the EXCB1-DC3-1 provides ample voltage and current margin.

4. Surge Protection Placement

The built-in Type 2 SPD (40kA Imax) is installed at the combiner box level, protecting the inverter’s DC input. For installations in high-lightning areas, consider adding a Type 1 SPD at the service entrance for a cascaded protection scheme. The EXCB1-DC3-1’s SPD can also serve as a standalone protector in moderate-risk locations.

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. Even for a single string, a combiner box with an integrated surge protector and disconnect switch is recommended for safety and to protect the inverter. The EXCB1-DC3-1 provides these functions for up to three strings, ensuring code compliance and simplifying wiring.

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, the combiner box output will be approximately 400V and 30A. Voltage is only increased by connecting panels or strings in series.

What does a combiner box do for solar panels?

A combiner box for solar panels consolidates the DC output of multiple solar strings into one or more protected outputs. It provides overcurrent protection per string (via DC circuit breakers or fuses), surge protection against lightning-induced transients, and a manual disconnect point for safe maintenance. The EXCB1-DC3-1 3 string solar combiner box performs all these functions for three strings, protecting the panel cables and the inverter while keeping the system organized and code-compliant.

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 overcurrent protection (MCBs or fuses), a surge protective device (SPD), and often a DC disconnect switch — 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 electrical codes. The EXCB1-DC3-1 is a dedicated solar combiner box engineered to IEC/EN 60947-3 and other relevant PV standards.