The Ultimate Buying Guide to Solar Combiner Boxes

Home 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

Inside of a solar combiner box
Source: Pinterest

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. Those that choose bifacial PV modules will find DC combiners to be especially helpful: They give the user the option to apply the proper fuses of at least 25 amps to offset the increased currents.

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. 

The combiner boxes allow you to store anywhere between two and six-string inverters in a single cabinet. They work in the harshest climate conditions and meet the highest market standards according to IEC 61439-2 ed 3.0:2020. They can resist ambient temperatures of -20 to +50 °C. 

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

The capacity to de-energize is the primary distinction between DC and AC combiner boxes. One of the main reasons for the protection of cross-level misoperation is the use of AC circuit breakers instead of DC circuit breakers or AC and DC circuit breakers mixed. 

This is due to the fact that the arcing and arc extinguishing methods used by AC and DC circuit breakers are different, therefore even breakers with the same rating cannot both turn on and off the DC power supply.

While the DC switch does not have a zero-crossing point, the ability to extinguish the arc is very weak, necessitating the insertion of a second arc extinguishing device, AC has a zero-crossing point at every cycle, making it easy to extinguish the arc at the crossing point. In essence, extinguishing an arc in DC is challenging, whereas extinguishing an arc in AC is simple with an overshoot of zero.

Circuit breakers for AC and DC systems are not interchangeable. The variations are as follows:

  • The two main contacts for DC and three for AC are different numbers.
  • The primary contact of DC and AC electrical appliances have different arc extinguishing device structures; the DC contact arc extinguishing structure is primarily of the magnetic blowing type, whereas the AC contact arc extinguishing structure is primarily of the grid type.
  • While a DC open of the same grade can typically be utilized momentarily for an AC occasion, an AC open shouldn’t be used carelessly for a DC occasion since a short circuit is more likely to result in more intense sparks. We can therefore use a DC circuit breaker to temporarily cover the gap when we don’t have an AC circuit breaker available, but we can’t constantly use it because the DC kairos ability requires high.

Three alterations must be taken into consideration when adapting AC circuit breakers to safeguard DC circuits.

Protection from overload

For overload long delay protection, thermal-activated (bimetallic components) are used. The action source is I2R, and since the RMS value of AC current is equal to the average value of DC, there is no need for any change. However, because the transformer cannot be utilized in the DC circuit for current heating, the secondary side of the current transformer is not used for high-current standards.

The AC complete electromagnetic release cannot be used in a DC circuit because the delayed-release characteristics must be adjusted and the minimum action current must be bigger than 110 percent to 140 percent if the overload long-delay release is hydraulic (i.e., oil-cup type) (if it is to be used, it will have to be redesigned).

Short circuit protection

The usage of a magnet system for hot-electromagnetic AC circuit breaker short circuit protection comes after the filtered rectifier circuit (DC), and it requires multiplying the initial AC set current value by a factor of 1.3. The thermal-active electromagnetic kind of protection offers complete electromagnetic short-circuit protection.

Circuit breaker accessories include things like shunt releases, Undervoltage releases, electric operating mechanisms, etc. Shunt and Undervoltage are voltage coils that can be utilized in both AC and DC systems as long as the voltage value is the same. Both AC and DC systems frequently use auxiliary and alarm contacts. When the electric working mechanism for DC is employed, it should be redesigned.


Arc extinguishing is challenging due to the lack of characteristics above zero, DC short-circuit current (or even a small multiple of the fault current) on and off; therefore, the wiring should be two or three poles in series, increasing the fracture, so that the fracture bear part of the arc energy.

Why Do We Need Combiner Boxes?

A 4-string solar combiner box
Source: Pinterest

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.
  • Serves as a quick shutdown mechanism in the event of voltage surges.

The solution is not that easy. It varies:

  • When the system contains strings of more than three PV modules.
  • Wish to make the inverter’s protection better.
  • For the aim of a quick shutdown in the event of abrupt changes in the current.

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.
  • Too much power and current can be prevented from entering the inverter by using the solar combiner box. To prevent overloading the inverter, the power connection will automatically be cut off. If people do this, they might avoid having to buy a new inverter, which might save a lot of money and hassle.
  • 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

AC Combiner Box
Source: Beny

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.


The solar combiner box must offer security. You may have read it. But what kind of protection are we seeking? There is an easy solution. It must work with the system and offer voltage and lightning surge protection. A perfect box would have a DC fuse to immediately shut off the power system as well as DC circuit breakers appropriate to the number of string modules.

Make sure that everything you choose complies with the legal code requirements in your location. Everyone must install a disconnecting combiner for the roof mount within six feet of the array, according to the 2011 rule. Few codes need an immediate system shutdown.

The electrical discharge between the conductors that are of great power and produces a lot of heat is called an arc fault. As a result, the insulation between the wires degrades. The best combiner box expertly protects your solar system.

Easy To Install

When it comes to the solar combiner box, installation is a major worry. The majority of us aren’t even familiar with electrical machinery. Protection is our top priority, and the simple-to-install combiner box can make that happen. Look for a plug-and-play box that has all the necessary features included as a result.


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.


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.


Depending on the materials being used, some spots can connect everything without a combiner. Without a combiner, the arcing voltage current can be handled by the BLA or Big Lead Assembly harness, a thick gauge of wire.

For solar installations with two or three strings, a solar combiner box is not required. Instead, attaching the string to the inverter might be beneficial. The use of combiner boxes is ideal for large projects with more than 4000 strings. In commercial applications, various box sizes are employed to extract power from unusual building configurations. For utility-scale projects, they aid site planners in maximizing electricity while minimizing material costs.


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.


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.

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

A DC Combiner Box produced by Beny
Source: Beny

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.

In the past, all inverters were simply grounded, and installers connected parallel strings to a combiner before connecting them to the inverter. Transformerless inverters are now available that are ungrounded, requiring installers to fuse the negatives. The layout requires a combiner box to bring everything together because it is more complex.

That is traditional straight paralleling if it is grounded. You will need to fuse the negatives and be able to detach both the negative and the positive if it is a transformerless device. The inverter size is another factor. You’ll need a combiner that can handle the 1,000 volts that so many inverters are currently producing.

Again, certain combiners are capable of handling numerous tasks. For instance, Beny’s product line can perform three tasks simultaneously in one configuration: a straight parallel, followed by a shootout to two different inverters. Alternately, that same box is capable of fusing up to four negatives and four positives for a transformerless job.

Cost of Solar Combiner Boxes

Solar combiner boxes typically cost between $100 and $300. The middle of these rates, or roughly $175, typically represents some of the highest quality solar combiner boxes. Even though it could appear like a costly investment, it is essential for large solar systems and can still be useful for smaller solar systems.

The gain in energy efficiency you will notice from a solar combiner box will enable you to quickly recoup its cost. In comparison to merely plugging your solar panels into the inverter, you will be able to extract more power from them. Your reduced electric bill will quickly more than offset the expense of a solar combiner box.


A DC plus AC Combiner Box
Source: Beny

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.

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