PV Array Wire Management

Securing, Supporting and Protecting Conductors within the PV Array

PV systems are expected to have a 25-year lifespan, and array wire management solutions should match this expectancy. However, designers and installers face persistent challenges to managing free-air conductors within the PV array.

Implementing a safe, reliable and Code-compliant wire management system for exposed PV conductors is not an easy task. PV module leads can be too long or sometimes too short, requiring site-specific solutions for supporting and interconnecting the cables. Equipment grounding, PV source-circuit and inverter-output conductors from microinverters and ac modules must also be managed to ensure protection from potential damage. Within the PV array, these various conductors are often secured to module frames, support rails and other racking system components. While securing array wiring seems like it should be a straightforward exercise, the reality is that integrators continue to face numerous challenges.

UV-rated plastic wire ties provide a flexible, convenient and low-cost solution for bundling and fastening array conductors, but they are not a permanent answer and require regular inspection and replacement. Stainless steel cable clips work well for attaching conductors to the module frame, but this solution is often limited to supporting only one or two conductors at a time, and not all modules have frames. Structural channels or integrated cable management solutions within the module support rails assist with protecting and routing conductors, yet precautions must be taken where conductors enter and exit the channels to protect them from sharp edges that may compromise their insulation. In addition, module rails tend to run either east-west or north-south, so they may not provide support where conductors run perpendicular to the rail alignment.

Unfortunately, the PV industry lacks consistent, standardized wire management solutions for free-air conductors within the array. Coupled with the harsh environmental conditions that PV array conductors are exposed to—UV radiation, high winds and extreme ambient temperatures, and ice, snow and other debris—wire management continues to be the Achilles heel of the majority of PV installations. In this article, I check in with several PV industry experts—from Code gurus and inspectors to installers and O&M providers—to better understand the industry’s current challenges, considerations, Code requirements and needs when it comes to managing and protecting exposed conductors within the PV array.

The Importance of Wire Management

The majority of PV systems have integrated leads, or wires, used for making electrical connections between modules. The module leads and the associated homerun conductors are often installed in free air within the PV array—meaning they are not in conduit. These exposed circuits contain potentially lethal voltages and currents that could electrocute someone, or cause a fire, in a faulted condition. As a result, we need wire management solutions that can endure the extreme environments in which PV arrays are installed while ensuring the systems are safe and reliable. 

The Consequences of Poor Wire Management

I have done quite a few fire investigations. While the specifics of many of these investigations are confidential, there are several types of problems where poor wire management contributed to failures. All of the following practices have caused fires in the field:

  • Putting USE-2 string conductors in contact with sharp edges, creating undetected ground faults that end up short-circuiting the array
  • Not properly identifying conductors and incorrectly polarizing combiner boxes, creating array short circuits and combiner box fires
  • Improperly installing thermal expansion fittings, especially in runs that require multiple fittings
  • Not properly accounting for thermal expansion and conductor weight, causing damage at roof edge fittings and boxes
  • Not properly addressing thermal expansion of conductors inside raceways, causing damage at box fittings
  • Improperly using stainless steel wire ties, putting too much stress on conductor insulation
  • Not fully seating plug connectors
  • Putting stress on junction box and plug connectors, causing them to fail and separate (which can cause an arc if under load)
  • Using improper torque procedures on combiner box terminals (It is common for combiner box terminals to loosen over time due to improper torquing or thermal cycling and vibration on rooftops.)

New mistakes are invented every day.

—Bill Brooks, president, Brooks Engineering

Pages

Article Discussion