The Ultimate Buying Guide to Solar Combiner Boxes

Nobody wants to choose the incorrect combiner box and unintentionally compromise the entire arrangement after selecting all of the panels, wiring, microinverters, and any analytical software, batteries, or storage. 

When selecting a combiner box, the project’s kind, size, and scope are crucial factors, just as when choosing any other product. What works well for a domestic installation won’t always work for a commercial installation, and so on.

It’s easy to choose the best combiner box for the work if you determine the site, other elements, and how they relate to the combiner. Consequently, today’s topic will be the ultimate purchase guide for a solar combiner box.

How Does A Solar Combiner Work?

The output of several solar strings is combined by the combiner box. Each string conductor lands on a fuse terminal as the output of the fused inputs is combined onto a single wire that connects the box to the inverter. Although this is the most basic type of combiner box, it usually has extra features once it is installed in your solar project. Disconnect switches, monitoring tools, and remote rapid shutdown devices are other pieces of equipment.

The box is similar to a junction box, which is an electrical container used to join several wires and cables through various entrance points safely. It combines the output of several PV module strings that help connect the inverter. It often houses the input overcurrent protection fuse assemblies for numerous strings. There could be anywhere from three to fifty-two strings.

Hardware for string monitoring, surge protection, and DC disconnects are additional parts that may be present in a solar combiner box. It is best to understand the task site and the degree of complexity to choose the ideal solar combiner box for your business. The other parts and how they work with the combiner should also be familiar to you.

AC vs DC Combiner Boxes

What is A DC Combiner Box?

In ground-mounted solar power plants, the DC combiner boxes are dispersed throughout the PV module array whereas the inverters are put in a single location. This results in minimum power loss on the AC side and short cable runs between the inverters and the transformer, allowing us to utilize the high efficiency of our inverters fully. This kind of construction makes it possible to avoid AC lines on the roofs in commercial and industrial PV installations.

One may customize the combiner boxes to your needs or the installation requirements of the location where they will be used thanks to the available configuration choices. For instance, it is extremely practicable to implement the need for arc fault detection as well as the capability for quick shutdown or a “fireman’s switch” for remote system disengagement. For bifacial PV modules, include the expected rear-side contribution in the current assessment. Size any required string fuses for the design current without exceeding the module’s maximum series-fuse rating or the conductor’s permitted current, rather than applying a universal 25 A minimum.

What is An AC Combiner Box?

Reliability and availability are crucial for solar systems in the PV sector. Beny’s AC combiner boxes offer the best short-circuit and overvoltage protection in systems with string inverters. Additionally, it is simple to isolate each string inverter from the system for maintenance purposes. 

An AC combiner box brings together the AC output circuits of multiple inverters; it does not normally house the inverters themselves. Select the number of circuits, enclosure, operating conditions and required compliance documentation for the specified model and installation.

For the solar PV AC side, there are specialized 230V-400V, 690V, and up to 800VAC combiner box solutions. The power transformation and distribution between various power sources have an AC distribution box. The solution consists of AC surge protection, an AC MCCB, or an optional NH00 fuse disconnect switch.

Differences Between AC And DC Combiner Boxes

A DC combiner box handles PV circuits before the inverter. An AC combiner box brings together AC circuits after the inverters. The protection and switching devices must be rated for the circuit where they are installed.

Do not substitute an AC-only circuit breaker in a DC circuit, or assume a DC-rated breaker is suitable for AC. A device may be used in both only where the manufacturer explicitly rates it for both applications and the proposed configuration.

Protection from overload

Select protection for the circuit current, conductor capacity and equipment limits. Apply the manufacturer’s ratings and derating instructions for the intended AC or DC duty.

Short circuit protection

Check the breaking capacity at the actual operating voltage and prospective fault current. An AC trip setting multiplied by a fixed factor does not establish a suitable DC rating. For example, the BENY BB1-63 specifications distinguish the rated DC voltage for different pole configurations.

Wiring 

Follow the approved wiring diagram for the exact device, including polarity and pole connections. Do not improvise series-pole wiring to obtain a higher voltage rating. Installation and electrical testing require qualified personnel.

Why Do We Need Combiner Boxes?

It is comparable to a junction box, an electrical enclosure that securely connects numerous wires and cables through a variety of entrance ports.

For many strings, it often houses the input overcurrent protection fuse assembly. There might be anywhere between three and 52 strings. A solar combiner box can also store a variety of auxiliary parts, including hardware for string monitoring, surge protection, and DC disconnects. 

The other parts and how they relate to the combiner should likewise be well known to you.

• The use of a solar combiner box can potentially save money by reducing the number of wires connected to the inverter.
• The number of connections to the fuse terminals is reduced thanks to the combiner box, which also makes it simple to understand and locate the necessary wires.
• A correctly selected surge protective device helps protect against transient overvoltages. Rapid shutdown is a separate system function and is not provided by every combiner box.

Consider an external combiner or protection box when the design has one or more of these needs:

• Multiple PV strings need to be combined into the output circuits specified by the inverter design.
• The installation needs external string protection, surge protection or isolation that is not already provided in the required location.
• The project needs a central point for string connections and any specified monitoring equipment.

People only need to be aware of the network’s complexity and implement the necessary safeguards. Some of the benefits of a solar combiner box include:

• Even though a solar combiner box is compact and straightforward, it has numerous advantages for the solar system. They maintain orderly wires to reduce energy loss from the panels to the inverter. The solar combiner box makes it simple to detach when repairs are needed and to reconnect after the necessary maintenance has been completed.
• It will be simpler to maintain and use fewer resources if people use the solar combiner box because there will be fewer cords hooked into the inverter. The safety and peace of mind that a solar combiner box offers may be its most significant advantage.
• Correctly selected protection helps address specified electrical faults. It does not replace matching the array to the inverter’s maximum DC voltage, input current and short-circuit current limits.
• A solar combiner box is also quite simple to install, and since they are so strong, there won’t be a need to bother about replacing them.

Insights of Solar Combiner Boxes Purchase

Finding a high-quality solar combiner box is the key. We’ll go through the key characteristics to consider in your perfect solar combiner box.

Quality Tool

Constantly having to purchase the same tool is a real pain. Keep this in mind: Never give in to price pressure at the expense of quality. You could be asking why. The main objective is to exert the tool for extended periods. Only if your box possesses the appropriate quality will you be able to accomplish this goal.

Protection 

Match each protection device to its task. PV fuses or circuit breakers provide the specified overcurrent protection; surge protective devices address transient overvoltages; suitable disconnecting devices provide isolation. Rapid shutdown and arc-fault detection require the appropriate equipment and system configuration.

IEC 62548-1 covers PV array design requirements, including wiring, electrical protection, switching and earthing. Apply the requirements adopted at the installation location and the equipment manufacturer’s instructions, including any rapid-shutdown provisions. Confirm the arrangement with the responsible installer or designer before ordering.

An arc fault can generate intense heat and create a fire hazard. Where the design requires arc-fault detection and interruption, specify equipment with that function, such as an appropriately configured AFCI solar combiner box. Do not assume an ordinary combiner box provides arc-fault protection simply because it contains fuses or surge protective devices.

Easy To Install

For easier installation, look for clear terminal labels, suitable cable entries, accessible mounting points and wiring instructions. Pre-wired or plug-and-play features can reduce installation work, but electrical installation and testing still require qualified personnel. Follow the manufacturer’s isolation and verification procedure; do not open the box or disconnect PV connectors while energized.

Adaptable 

The issue is not the same everywhere. For instance, the environment in the workplace and the home are very different. A good combiner box can therefore be adjusted to the existing circumstances. high temperatures, as an illustration. Find a compatible box that operates under the specified circumstances by doing so.

Affordable 

Everyone wants to reduce their overall purchase costs. Only when you examine and contrast several items is it possible. You must write down your requirements in the case of the combiner box and then look for them there. If it has all the features, it’s time to look for the greatest option at a reasonable price. To explore top-rated models, check out our guide on the Best 5 Solar Combiner Boxes for Your Consideration.

Necessity 

Some PV systems connect their strings directly to suitable inverter inputs and do not need an external combining stage. Check the inverter’s input arrangement, built-in protection and installation instructions before adding a separate box.

Two or three strings alone do not settle the decision. Review the required output circuits, current limits and external protection for the actual installation. For a deeper understanding of this topic, read our guide on Solar Combiner Boxes: Why We Need Them.

Management

The makers have gathered wireless monitoring technology inside the combiner box. This guarantees voltage, current, and temperature monitoring at the string and panel levels. Along with the benefits that are already there during the installation, monitoring offers real-time feedback when assigning the field. Any errors or flaws will be identified early in this method.

Solar combiner boxes require some upkeep. The environment and usage patterns must be taken into account while determining the level of maintenance. Although checking them for leaks and loosened connections sounds like a good idea, a properly fitted solar combiner box would last for the duration of your project.

Since the combiner box is the first piece of equipment connected to the output of the solar module, quality is likely the most important consideration when making your choice. When compared to other solar project components, combiner boxes are fairly inexpensive. Keep in mind that a malfunctioning box could result in a sudden failure with smoke and flames.

The whip is a brand-new feature. It is a wire that is laying at the solar connector’s end. Whips are fastened by the makers, allowing the installer to connect output wires using a solar connection. The contractor is required to obtain fittings or drill holes.

Operation

The choice of your solar combiner box may occasionally depend on its availability and cost. For home installations, there are a few ready-made options with a variety of possible configurations available, saving the additional cost and effort associated with anything personalized.

Now, depending on the parts of your system, the combiner box could need to do more than just combine fuses and circuits. Not all manufacturers have the best combiner box available off the shelf for every circumstance. Do you desire flexibility and simplicity? Assume you have two distinct solar systems that connect to the same box and then radiate out to separate controllers. Some boxes instantly solve this issue, while others require customization.

Please identify the inverter being used before selecting a combiner. You must select just the combiners that adhere to the code out of the numerous options available, which range from traditional string inverters to transformer-less with MPPT.

How to Size a Solar Combiner Box

Start with the module and inverter specifications, not just the total array power. A module is one solar panel; a string is a series-connected group of modules. The box’s input count refers to strings, not individual panels.

Five checks before choosing a configuration

Check	What to confirm
Inputs and outputs	Count the strings and identify the output circuits needed by the inverter. Keep independent maximum power point tracking (MPPT) circuits separate as required by its design.
Maximum DC voltage	Use string open-circuit voltage corrected for site conditions, including low temperature, rather than operating voltage alone.
Current and protection	Check string and combined-output currents separately, alongside module fuse limits, conductor capacity and inverter input limits.
Installation environment	Specify heat, sunlight, moisture, dust and any corrosive exposure. Check enclosure and component suitability for that location.
Quotation details	Agree the circuit diagram, device configuration, cable entries, labels and required documentation before ordering.

For example, BENY’s BHS-6/3 and BHS-6/6 both accept six PV strings, but provide three and six output circuits respectively. Choose the configuration that matches your inverter’s input layout.

Not sure which model you need? Contact BENY with your panel and inverter models, string layout and project location. Our team will help you choose a suitable combiner box.

What Features Do You Most Require In A Solar Combiner Box?

Your decision on a combiner box may simply depend on availability and price. There are pre-packaged systems that can fit in a range of possible configurations for a residential installation, saving the time and additional costs associated with a custom solution.

The combiner may need to do more than just combine circuits and fuses because there are so many different possible panel configurations, and this will rely on the other parts of the system. Not every manufacturer has the ideal off-the-shelf combiner box that is prepared for each unique circumstance. 

Do you require flexibility, or are you merely looking for simplicity? Imagine you have two distinct, totally different solar power systems that connect to the same box and then radiate out to separate controllers. Some boxes can handle that with ease, while others could require custom construction.

Confirm the array’s earthing arrangement, the inverter manufacturer’s instructions and the locally applicable requirements. Use these to determine which conductors need overcurrent protection or isolation; the word “transformerless” alone does not define the complete protection scheme.

Select the voltage class using the array’s maximum open-circuit voltage, corrected for low temperature. Check it against the voltage ratings of the box, its components and the inverter. Do not assume every installation requires the same 1,000 V configuration.

Also match the box’s output circuits to the inverter inputs. BENY offers different input/output arrangements, so send the inverter model and string layout to BENY before choosing the configuration.

Cost of Solar Combiner Boxes

The cost of a solar combiner box depends on its input/output arrangement, voltage and current ratings, protection devices, enclosure, monitoring options and required documentation. Compare quotations against the same specification rather than judging quality by price alone.

Include installation work and maintenance access in the comparison. A suitable design may simplify cable routing, but a combiner box does not create additional solar energy or guarantee a fixed payback period. Send your project requirements to BENY for a configuration-specific quotation.

Conclusion

The globe has been dominated by solar energy. However, this idea is slowly being embraced by the entire world to successfully use renewable energy sources like solar energy, and solar combiner boxes can boost your solar system’s effectiveness and safeguard the inverter from excessive voltage or current.

In addition, there are threats to your safety. What if there is a power spike, for instance? Beny’s solar combiner box helps us deal with the situation. Contact Beny for high-quality products.