Installing PV Wire: Direct Burial, Hangers, or Conduit?

PV wire doesn’t seem like a big deal, but moving generated power from solar panels to the electrical grid would be impossible without it. 

To the untrained eye, installing thousands of feet of wire seems like a pretty straightforward process. But maximizing its performance depends on several factors, including: 

• Environmental Conditions  
• Cost Considerations  
• Ease of Installation  
• Project Size

Depending on the situation, solar EPCs have a few installation options, including direct burial, conduit, and hangers. 

Direct Burial Installation 

When solar developers directly bury PV wires, they install them in trenches underneath the panel rows. 

Direct burial wire is designed for underground installation without a conduit. To ensure the wire is up to the task, it undergoes rigorous testing to earn a specific UL mark. In this case, the mark signifies the wire can withstand abrasions, crushing, moisture, chemicals, and other hazards. 

Solar companies like direct burial wire because it’s a low-cost and easy way to install electrical wiring. Workers only need to dig a trench along the panel aisle near the racking, place the wire, and cover it back up. But as easy as it is, direct burial wire isn’t appropriate for every application. 

The Good and the Bad of Direct Burial Wire 

Soft soil compositions with relatively few rocks are the best conditions for direct burial wire. Sandy soil is also a good option because it drains quickly. Drainage is vital for underground wire installations because moisture can damage wire insulation and jacketing over time. 

Direct burial wires also run the risk of damage from environmental hazards. Sharp rocks could nick wire insulation, allowing moisture to get in. Large rocks can crush the wire and its insulation, hurting performance. Even damage caused by rodents chewing on the wire can potentially create faults. 

Damage could lead to less electricity generated and create unsafe conditions. It also costs crews time, money, and long-term production since they must visit the site, dig up damaged wires, and repair or replace them. 

Underground Conduit Installation 

Conduit installation is similar to direct burial, but instead of putting the wires in the ground, they’re fished through metal or PVC tubes. 

The tubing provides an additional layer of protection on top of the wire’s standard thick insulation and works well in rocky, moist, or corrosive environments. Typically, conduit is used when crushing, abrasion, or other threats are an issue. Beyond soil, conduit protects the wire from rodents, temperature fluctuations, and accidental damage from digging. 

Unlike direct burial situations, workers can easily replace or repair wires if something goes wrong – without digging. Crews only need to pull the wire out, replace it, and fish it through the conduit pathway. 

Like any other electrical project, local regulations may dictate conduit use. Requirements could change from one municipality to the next. The National Electrical Code (NEC) also has specific standards, so keep them in mind. 

More Protection, Higher Costs 

Encasing wires in conduit offers better protection than insulation alone, but makes solar projects more expensive. 

Not only do you have to buy enough for the entire site, you need people to install it. This means digging trenches, burying the conduit, then pulling wires through the tubing to connect everything. And as utility- or community-scale solar sites get bigger, so do the associated costs and timelines. 

Conduit is also not as flexible as direct burial wire, making it harder to use on slopes and curves. Shovels or excavators could also accidentally puncture metal or PVC conduit, damaging the contained wire. 

Cable Hangers 

Hangers come in many shapes and sizes, using galvanized steel coated with thick PVC to safely hold PV wires in place from the solar panel to the combiner box. 

Unlike conduit, workers can easily bend hangers to fit whatever shape they need. And unlike direct burial and conduit solutions, hangers don’t require any digging. They connect directly to the racking underneath the solar panels and provide a cost-effective way to string PV wire quickly across difficult terrain. This makes them useful in areas where the ground isn’t suitable for digging, like brownfields. 

Depending on the number of wires carried along the pathway, messenger wires might be necessary. Unlike PV wire, messenger wires don’t carry any current – they provide strength and support to keep wires in position. 

Maintenance and repair work is also easier for operators because the wires live in the open air. Workers can find damaged wires, remove them from the hanger system, and replace them without additional equipment. 

PV Wire Hanger Considerations 

As with any electrical job, PV wire hangers fall under NEC guidelines. 

According to NEC Article 690.31 (C) (1) (b), “Exposed cables sized 8 AWG or smaller shall be supported and secured at intervals not to exceed 600 mm (24 inches) by cable ties, straps, hangers or similar fittings.” 

The rules are slightly different for wires bigger than 8 AWG, allowing hangers up to every 54 inches. For added support, messenger wires can help carry some of the weight. 

Depending on the location of the solar array, code enforcement could apply other rules. Contact your local codes department to avoid any potential issues. 

Above-ground wires also face several potential issues, including contact with people and vehicles and severe weather. Buried wires are typically hidden, but hanging wires don’t have the same type of protection. This leaves them open to damage from sun, wind, rain, snow, vandalism, and accidental contact. 

What Impacts Solar Wire Installation? 

No two installations are alike, but knowing what you’re getting into before putting shovels in the ground can make mistakes avoidable. 

Environment 

Soft soil without much moisture is well-suited for direct burial projects. If the soil is rocky, struggles with drainage, or risks contact with chemicals, conduit makes sense. If the land is rocky, too wet, or at a brownfield site, hangers are a safe, cost-effective choice. 

Cost 

Direct burial is a low-cost option but requires laborers to dig trenches. Hangers are also cost-effective but leave wire out in the elements and exposed to other dangers. 

Conduit is pricier and requires labor, time, and equipment. However, it offers solar systems the best protection from damage and exposure. 

Project Size 

Bigger sites mean more work and longer timelines. Worse yet, delays can occur if crews run into unexpected issues. 

Smaller community-scale solar energy projects take less time to wire compared to utility-scale solar projects. However, smaller sites may benefit from the added protection conduit offers without a massive hit to the bottom line. As sites become larger, costs increase dramatically, forcing project developers to limit expenses. 

Code Regulations 

Although the NEC is an excellent guidebook, follow local and state codes to avoid mistakes. 

Failing to do so could result in violations, leading to work delays, fines, or other problems. 

Know Your Surroundings 

As solar sites spring up across the United States in brownfields, farmland, and even on water, teams should carefully determine how to set up their arrays.

Whether it’s a utility company with a small solar farm in the rolling hills or a large-scale developer repurposing brownfields, having the right manufacturing partner makes a huge difference. 

Good partners understand community, industrial, and utility-scale installations and act as a guide. They can also field questions and offer insight throughout the blueprinting, development, and troubleshooting processes. 

Most importantly, companies can keep every solar job on time and within budget.