Best Wire Management Practices in Railed and Rail-less Solar PV

Properly securing PV conductor wires is critical to the productivity, safety, and longevity of your solar array. Whether you choose to install a rail based or rail-less, also known as direct-attach system, these practices are vital. They help ensure a safe and durable system is installed and that the wires will be shielded from exposure to sunlight, rain, snow and wind, as well as protected from sharp abrasions and edges, and to discourage animals from chewing on hanging wires. In this video, we will cover the best practices for minimizing and organizing PV wires for both small and large scaled solar projects. Look for our top takeaways to help you put each best practice into action In the first stage of wire management in rail based or rail-less designs, when you're installing and wiring together a single string of modules, the conductors are plugged together and the wires need to be clipped to the frames and cannot sag.

But it is after this where the two install methods begin to deviate. We often get questions from installers who are looking for guidance on how to route the wiring from the string ends to the home run. This step is crucial with any PV system. It's usually not too difficult with small residential installation, but it can be a bit more complicated to plan out and execute for larger commercial systems. Here are some of the common questions installers ask us when they're beginning their wire management planning. How do you lay out the wires while also minimizing them all over the roof? What do you do if your string ends in the middle of an array and you have to run wire from the middle of the array where the home run starts, usually at the edge of the array? How do you know whether to use conduit or cable trays for wire management? Or do you just zip, tie the wires to the modules or both.

When the conductor wires are bundling up, how do you plan where to attach them or whether to use wire trays? How do you install or mount module level power electronics optimizers and microinverters, when using direct- attach. We've put together a list of the best practices to help answer these questions and guide installers in PV installation when using the direct-attach, rail-less method, and we offer comparisons to railed systems to help demonstrate the installation efficiency of the direct- attach method. Thinking about how the modules will be laid out beforehand will help you minimize the wires all over the roof. You can design the strings to minimize the wires needed to route the power from the strings to the inverter. And we'll show you two ways to lay out your wires and explain how you can save time and money by choosing the right wire design for your roof.

The first option is the Direct Method. This method enables you to lay out your modules and strings close together. On the right you can see that it will take a lot more wire to get to the home run. This is why your string design is so important. Design your strings to make it easier to wire them together. The Direct Method involves running each string of connected modules down, or up as the case may be, the panels to the home run. These wires can be laid out ahead of module installation or as module installation progresses.

Whether you choose to install ahead of time or on the fly, the direct method generally results in more time on site and higher labor costs on a project of this size. The second wiring option is the tree trunk method. This is another way to layout panels and strings, which offers benefits over the direct method. Note, the strings in the right image have the conductor ends, pluses and minuses, more organized for bundling and routing. This method will simplify your wires so that you can bundle them together when running them to the home run.

The trunk design requires more planning before and after you get up on the roof. This method generally requires the use of cable trays or conduits to protect the wires, so you must lay out your wiring on the roof before you install the modules. With this method, the trunks can be large bundles of conductors laid in wire trays, saving you labor time tying up all the conductors. While some hard goods cost is incurred for cable trays or conduits, when using the tree trump method, it greatly simplifies your wire routing and associated labour by eliminating the management of random strings all over the place. Let's compare the two methods. In the direct approach, you have to attach all the wires individually to the modules frames, or PVKITs, as the modules and PVKITs are installed on the fly. This approach is preferred by some installers, but when you compare this to the second method, these two fundamentally different approaches can vary widely in cost.

Ultimately, you can save time and money by using specific wiring designs such as the trunk method. The Trunk Method requires more work to be completed before module installation because of all the wires that must be in place first. The crux of this is that you bundle a handful of wires, than run these trunks in your wire management trays to the home run. This method is considered by many to be more organized and easier to deal with on a project of this size. System size, however, dictates further consideration. On smaller projects, this may or may not be the case. How do these two wiring methods relate to residential or small commercial projects? Here's an example of a residential PV project with 30 modules and approximately 8-10 kW of output.

The direct method is fine to use for this size project. Ssing this method often makes residential sized projects much simpler. This is because you only have a few strings, a few conductors, and much smaller wire bundles to deal with. When going rail-less with the S-5! PVKIT, you can tie the wires to the slots on the PVKIT, rather than clipping them to the module frames. And lastly, you can simply use small conduit for the home runs. With a residential or small commercial system, you only have a few wires, so you can just run the wires where you need them and clip them off the roof as you install the modules on the fly. In this scenario, the direct method is quite manageable and more expedient. When dealing with a commercial project, the quantities of conductors going to the inverter can be daunting for a large system.

The direct method quickly becomes very messy and inefficient. It can be done, but it's not generally advisable for a large system. The trunk method, or similar method of organizing wires, pays off with less labor and a cleaner, neater system. Note, the image below illustrates the S-5! PVKIT in its first rendition. In this version, the PVKITs had to be installed along with the wires before module placement. The updated PVKIT 2.0 does not require this. The new design enables installers to lay and play the PVKITs as modules are being installed. It is strongly advised that all conductor wires under the arrays be laid in place before modules are installed. It is possible to locate and attached to conductors on the fly, but it becomes messy and inefficient with larger systems.

This is where the trunk method using wire trays really pays off with less labor. Once you begin installing the modules and the PVKIT 2.0s, conductors can be clipped to the module frames or wire tied to the PVKITs as they're being installed. Something else to consider with commercial PV projects is the importance of organizing your wires. It is important to note that once you get to the home run, the two wiring methods we have discussed converge again and it doesn't matter whether you are mounting the PV with rails, or using direct-attach, rail-less. Here's an example of how to organize your wires with wire trays under the modules.

The trunks of the wires can be run in wire trays and the trays can generally be open and uncovered since they are underneath the modules and protected from UV and weather. Now we'll cover a few of the best practices that relate to both residential and commercial sized PV projects. These tips deal with circuitry and wire protection. You should troubleshoot after you finish each string. This is a great time to test the circuitry of the system during, rather than after, when it might be more difficult to locate an issue. There are a few ways to protect your wiring. Home runs are enclosed or open trays to carry bundles of conductors and ground wires from a PV array to inverters. Trays generally need to be covered if out in the open, exposed to the elements. You can also use the combiner boxes to reduce the quantity of wires for certain types of inverters. In addition, we advise you to position the home run on the ridge side of the roof in residential applications. Here is an example of a conduit being used as a home run to route the wires from the solar array to the inverters.

This method is used when you want to ensure the wires are basically sealed in the conduit and protected from weather conditions. This illustrates the wire tray uses a home run. Wire trays are more common because it's easier to put the wires in these instead of pulling them through tens or hundreds of feet of conduit. The cover protects the wires from UV exposure, direct rain, and snow. Module level power electronics refers to optimizers and microinverters. Not every project uses these electronics but they can easily be installed in rail-less PV systems.

One common option is to attach optimizers and microinverters to module frames before mounting on the roof. By attaching these electronics to the modules beforehand, you can stage them for easy access as needed during installation. An alternative to attaching module level power electronics to the modules is to mount them directly to the roof. Your solar array is a major investment and choosing the correct system for managing your wiring will not only help ensure the longevity of your PV project but will make future maintenance easy to manage.

Not to mention help keep your material and labor costs to a minimum. Download our checklist for choosing the best solar mounting systems at the link in the description, to help you evaluate the best option for your project. And log on to the Solar Solutions page of our website to find more facts, case studies and continuing education. Thank you for watching.

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