How to Choose a Combiner Box?

Introduction

Recent years have seen a rise in the popularity of solar power systems, which can be attributed to the movement toward the use of renewable energy as well as the cost reduction of solar panels. The combiner box is an essential element of a solar power system. How can you choose the best one for your requirements when there are so many different options available on the market? In this piece, we’ll walk you through the steps of selecting the ideal combiner box for your solar power system so you can get the most out of it.

What Is A Combiner Box?

In the context of solar power systems, a “combiner box” refers to an electrical device that is used to combine the output of several solar panels, often known as “strings,” into a single connection point. The combined current is then fed into the inverter at this connection point, which converts the direct current (dc) to alternating current (ac) so that it can be used in your home or business.

Types Of Combiner Boxes

There are three main types of combiner boxes available:

Standard combiner box: This type of box simply combines the output of multiple solar panel strings without any additional features.

String monitoring combiner box: This box not only combines the output of solar panel strings but also monitors the performance of each string individually.

Smart combiner box: This advanced box combines the output of solar panel strings, monitors their performance, and can communicate with other system components, such as inverters and energy management systems.

Why Use A Combiner Box?

A combiner box offers several benefits:

Simplifies wiring: By combining the output of multiple strings into a single connection point, the combiner box makes wiring the solar power system easier and more organized.

Safety: Combiner boxes include safety features such as fuses or circuit breakers, which protect your system from damage due to overcurrent or short circuits.

Monitoring: Some combiner boxes enable you to monitor the performance of individual strings, helping you identify issues with solar panels or wiring.

Products and reference designs of Smart combiner box

Input power protection

As the solar combiner box is placed in front of an inverter stage, it has to face weather-induced power surges, which the system electronics need to withstand. An eFuse will provide protection from overvoltage, overcurrent or short-circuit events. Input power protection includes eFuses & hot swap controllers, the corresponding products are TPS2400、TPS25921L、TPS2662

High side current sense

Accurate and high speed sensory data of the power bus in a stationary solar combiner box is required to effectively control the power electronics and help ensure operational safety. Isolated sensory techniques are routinely used due to the high voltages involved. High side current sense includes General-purpose op amps、Precision op amps (Vos<1mV)、Instrumentation amplifiers、Comparators、Analog current-sense amplifiers, the corresponding products are OPA2991、OPA376、INA333、TL331LV、INA211

Analog front end

After signal conditioning, the current is converted to a digital value for the MCU with an ADC. An optional reference might be required. Analog front end includes General-purpose op amps、Precision op amps (Vos<1mV)、Instrumentation amplifiers、Precision ADCs、Precision DACs (≤10 MSPS), the corresponding products are TLV9004、OPA376、INA333、ADC101C027、DAC101C081

Digital processing

The power stages in the solar combiner box system are controlled by a MCU. It converts the signals given from the current sense stage and brings it to the user by various interfaces. Digital processing includes MSP430 microcontrollers, the corresponding products are MSP430G2553、MSP430FR5729

Logic

Level shifters or other signal conditioning may be needed to use different interfaces. Logic includes Noninverting buffers & drivers、Inverting buffers & drivers、AND gates, the corresponding products are SN74LVC1G125、SN74LVC1G06、SN74LVC1G08

Output user interface

The interaction between the user and the system must be easy to use and understand. These requirements can be achieved through the use of displays and LEDs. With the output interface, the end user can quickly and easily monitor the solar combiner box. Output user interface includes LCD & OLED display power & drivers, the corresponding products are TPS65130、TPS65131

Wired interface

This subsystem enables communication between the MCU and the user with common interfaces, monitoring the system. Wired interface includes RS-485 & RS-422 transceivers、Ethernet PHYs、RS-232 transceivers、Isolated RS-485 transceivers, the corresponding products are SN65HVD3082E、DP83867IR、MAX3232E、ISO3088

Wireless interface

Wireless communication enables remote monitoring and control of the combiner box. Wireless interface includes Wi-Fi products、Sub-1 GHz wireless MCUs, the corresponding products are CC3200MOD、CC1350

Isolated DC/DC power supply

A solar combiner box may have many different voltage domains. Some are hundreds of volts above others. For each isolation domain, a dedicated power supply is required to ensure the high side sensing electronics have stable power and enough to drive high current FET gates, in some cases. Isolated DC/DC power supply includes Transformer drivers、Buck modules (integrated inductor)、Isolated DC/DC converters & modules, the corresponding products are SN6505A、TPSM828511、LM5017

Non-isolated DC/DC power supply

The internal electronics of a smart combiner box system require a number of separate voltage rails. MCUs and other digital controllers will typically run at 3.3V////; however, some digital processors operate at voltages like 1.2V. Non-isolated DC/DC power supply includes Buck controllers (external switch)、Linear & low-dropout (LDO) regulators、Buck converters (integrated switch)、Charge pumps (inductorless)、Multi-channel ICs (PMICs), the corresponding products are LM5145、TPS737、TPS62902、TPS60141、TPS51200

Power monitoring

To help ensure all the different rails give the correct value, an optional supervisory socket can be added. Power monitoring includes Supervisor & reset ICs、General-purpose op amps、Comparators, the corresponding products are TPS3803、OPA2991、TL331LV

Installation Considerations

When installing your combiner box, keep the following in mind:

Location: Place the combiner box close to the solar panels to minimize voltage drop and reduce the amount of wiring needed.

Accessibility: Ensure the combiner box is easily accessible for maintenance and troubleshooting.

Mounting: Mount the combiner box securely to a wall or other sturdy surface to prevent damage from wind or animals.

Wiring: Use high-quality wires and connectors to ensure a reliable connection between the combiner box and the other system components.

Maintenance Tips

It is essential to do routine maintenance on your combination lock box in order to ensure that it will last as long as possible and function to its full potential. Here are some helpful suggestions:

Examine the combiner box for any indications of damage or wear, such as cracks in the enclosure or terminals that have corroded.

Check the fuses and breakers in the circuit to make sure they are working properly, and replace them if any of them are blown or broken.

It is important to thoroughly clean the inside of the combiner box, removing any debris and dust that may be affecting its operation.

You should check the monitoring capabilities of the combiner box (if it has such capabilities) to ensure that they are accurately tracking the performance of the solar panel strings you have installed.

Cost Of Combiner Boxes

The price of a combiner box can vary considerably depending on its functions, brand, and physical form. Standard combiner boxes tend to be more reasonably priced, in contrast to string monitoring and smart combiner boxes, which tend to have a higher price tag due to the advanced functionality that they provide. You should look around and compare prices in order to get a combiner box that is both within your price range and satisfies your requirements.