How to Choose the Right Solar String Combiner Box for a PV System?

    After selecting solar panels, PV cables, inverters and other battery or storage devices, you don’t want to accidentally ruin your entire setup by choosing the wrong combiner box. When choosing a solar string combiner box, the type, size and scope of the project are critical, and what works best for residential installations may not work for commercial installations, and vice versa.

    Choosing the right solar string box for your PV system is not difficult, but you must understand the site, other PV modules and their relationship to the combiner box.

What is a Solar Panel Combiner Box?

    Solar panel combiner boxes combine incoming power into one main feed, which is then distributed to solar inverters. By reducing wires, labor and material costs are reduced. The solar panel combiner has built-in overcurrent and overvoltage protection to improve the protection and reliability of the inverter.

    The purpose of the solar combiner box is to combine strings of solar panels into a single box. Each string is connected to a fuse terminal, and the output of the fuse terminal is bundled into a cable that goes into the inverter box. This is the most basic function of the solar combiner, and it can be enhanced with additional features such as quick-close buttons and monitoring devices.

    There is a solar PV combiner box between the inverter and the solar panels. The location of the PV solar combiner box must be a top priority, as improper placement may result in a loss of electrical efficiency, and a PV combiner box is not required for homes with no more than three strings. Layout is critical as a less-than-ideally located PV combiner can result in increased DC BOS charges due to voltage and power losses.

How Easy is it to Set Up?

    In general, the ideal DC combiner box often depends on its ease of deployment and installation, as well as the hassle it removes from the project. Boxes with pre-wired fuse holders with pigtails can be a plug-and-play solution that does not require a licensed electrician to install.

    For example, Slocable released its Integrated DC Combiner Solution (ICS), a one-stop solution that includes pre-wiring, strain relief cable glands, touch-safe power distribution blocks and two-way fuse holders. If we save as much time and cost as possible with a turnkey solution that is simple and feasible, installers will incorporate it into every project.

What Function does the PV DC Combiner Box Need?

    When choosing a PV DC combiner box it comes down to price and availability. For residential installations, there are off-the-shelf solutions that encompass a variety of potential configurations, saving the time and extra expense involved with custom solutions.

    However, with many different panel layouts, and depending on other components in the system, the PV combiner may need to perform more than the basic function of combining circuits and fuses. Not every manufacturer has an ideal off-the-shelf solar DC combiner box for every situation. Do you need flexibility, or just simplicity? Let’s say you have two completely different solar systems that both run into the same solar DC box and shoot to separate controllers. Some combiner boxes can handle this, while others may require customization.

    In the past, all inverters were just grounded, and installers would parallel them into a solar PV array combiner box before connecting them to the inverter. Ungrounded transformerless inverters are now available, requiring the installer to fuse the negative pole. This layout is more complex and requires a PV array combiner box to hold them together.

 Before choosing a PV array combiner, you must first determine the inverter – what inverter to use? With so many inverter options, from traditional string inverters to transformerless and transformerless with dual channel MPPT, we had to narrow the specification-compliant disconnecting combiner box to several solutions covering all configurations.

    If it’s grounded, it’s an old-fashioned straight-line parallel. If it’s transformerless, the negative must be fused and be able to disconnect the negative and positive. Then there’s the inverter size, a lot of inverters now go up to 1000V and you need a PV array box to match.

    Also, some solar array combiner boxes can handle multiple tasks. For example, MidNite’s MNPV8HV can do three things simultaneously in one configuration: directly parallel, then shoot out to two separate inverters. Alternatively, the same array combiner box can handle transformerless operation and fuse up to four negatives and four positives.

    Some manufacturers can bundle wireless monitoring technology into solar system combiner boxes, enabling panel-level and string-level current, voltage, and temperature monitoring. In addition to its inherent advantages during installation, monitoring provides real-time feedback during field commissioning. In this way, problems can be identified in the first place and larger errors can be prevented in the future. There is an element of human error in any construction project, and careful inspection can avoid a many unnecessary expenses.

    The electrical combiner box requires little maintenance, and the degree of maintenance should be determined by the environment and frequency of use. It’s a good idea to check them regularly for leaks or loose connections, but a properly installed combiner box should extend the life of your solar project. Quality is the most important consideration when choosing a photovoltaic combiner box, especially since it is the first piece of equipment connected to the output of a solar module. Photovoltaic combiners are inexpensive compared to other solar project components, but a faulty combiner box can lead to serious failures such as fire and smoke.

Do I Need a PV String Combiner Box?

    Depending on the other materials used, some locations be able to connect everything without using a PV string combiner box. For projects with only two or three strings (e.g. ordinary residences), string combiner boxes are not required, and are only required for larger projects, ranging from 4 to 4,000 strings. On the other hand, string combiners can benefit in projects of all sizes.

    DC string combiner boxes can bring a limited number of strings to a single area for installation, disconnection and maintenance in residential applications. DC combiner boxes of different sizes are often used in commercial applications to harvest power from building layouts. Combiner boxes allow site planners to optimize power boxes while reducing material costs for utility-scale projects.

    A solar power combiner box that costs less than a few hundred dollars adds a lot of value to your solar system—fewer wires, higher efficiency, emergency disconnects, and improved safety. Not only do they have these advantages, but they are also simple to set up. If you have any other questions about the power combiner box, you can contact us, Slocable will give you the best solution and the best price!