Cable Tray for Solar PV Plants: Routing, UV Resistance and Grounding

A photovoltaic plant puts cable management through a harsher combination than most buildings: full-sun UV exposure, wide temperature swings, corrosive soils, rodents, and DC voltages now reaching 1500 V. IEC 62548 sets design requirements for PV arrays and IEC 60364-7-712 covers PV power supply systems; IEC 61537 covers the tray and ladder systems themselves. The practical decisions are material and corrosion class, tray type for heat dissipation, and whether the DC and AC sections are separated correctly.

Where Cable Tray Is Used in a PV Plant

Tray is not used across the whole array — most DC string cabling runs on the module structure or in buried ducts. It appears at the points where conductors converge:

• Combiner box to inverter. DC home-run cables, where currents are high and the number of parallel conductors is significant.
• Inverter station and skid area. AC output cabling, auxiliary power, and control cabling between the inverter, transformer and switchgear.
• Inverter to substation / point of interconnection. AC collection circuits, often the longest tray runs on the site.
• Battery energy storage containers. DC bus cabling between battery racks and power conversion equipment, where tray must handle large conductor sizes.
• Operation and maintenance buildings. Standard building services distribution, where indoor practice applies.

Choosing the Material: Corrosivity Drives the Decision

ISO 9223 defines atmospheric corrosivity categories from C1 (very low) to C5 (very high), with CX for extreme offshore and similar environments. Matching the tray material to the category is the single most consequential decision on an outdoor PV site.

For steel, coating thickness is measurable and should be verified on delivery. For painted or powder-coated finishes, confirm the specified system and its stated durability range under ISO 12944, and confirm UV resistance with the coating supplier’s exposure data rather than assuming any exterior powder coat is UV-stable.

Tray Type, Fill and Heat Dissipation

PV DC cables to EN 50618 (type PV1-F) and PV wire to UL 4703 are rated for high conductor temperatures — commonly 90 °C continuous with a higher short-term limit — and they sit in full sun. That combination means heat dissipation governs the design:

• Ladder tray is usually preferred for power runs because the open rungs allow air circulation and reduce the effective grouping derating compared with a solid-bottom tray.
• Perforated tray is acceptable where smaller conductors are used, but check the fill and grouping correction.
• Solid-bottom tray or covered tray protects against rodents and mechanical damage but traps heat; where it is necessary, apply the appropriate grouping and installation correction factors and confirm the resulting ampacity with the cable manufacturer.

Fill and grouping correction is not optional. IEC 60364-5-52 gives correction factors for groups of cables and for installation conditions; NEC 392 sets out ampacity rules for cables in tray, including limits for multiconductor cables in ladder and ventilated tray. On high-current DC home runs, several parallel single-core conductors per phase are common, and their arrangement affects both ampacity and the inductive loop — hence the routing rule below.

Routing Rules That Matter on DC Circuits

1. Route the positive and negative conductors of the same circuit together. Separating them creates a large loop area, which raises inductance and worsens the voltage transient seen by equipment during a fault. IEC 62548 addresses PV array wiring design; keeping conductors of a circuit in the same tray, bundle or conduit is standard practice for this reason.
2. Keep DC and AC circuits separated where practical, to avoid coupling transients from inverter switching into instrumentation and control cables.
3. Respect minimum bending radius at every change of direction, using the cable manufacturer’s stated radius for the actual cable diameter — PV cables are often larger in diameter than their conductor size suggests.
4. Provide drip loops at every cable entry into a combiner box, inverter or enclosure, so water runs away from the gland rather than along the cable into it.
5. Do not use the tray as a support for pulling tension. Use rollers and pulling heads; measure tension on long pulls.

Application Scenario / Case Analysis: Ground-Mounted Plant, Array to Inverter Station

Scenario constraints

A ground-mounted plant feeds 1500 V DC home runs from combiner boxes into an inverter station, then AC collection circuits run approximately 200 m of outdoor tray to the substation. The site is 15 km from a coast, with salty night-time humidity, high daytime UV, an ambient range of −5 °C to +45 °C, and a known rodent population. O&M staff want visual inspection access without removing covers.

Selection approach

• Assess corrosivity first. Coastal proximity with salt-laden humidity typically pushes toward ISO 9223 C4, which rules out plain hot-dip galvanising as a long-life answer; consider 316 stainless or a documented FRP system, and specify compatible fixings.
• Use ladder tray for the DC home runs to keep conductor temperatures down, and confirm the grouping correction with the cable manufacturer for the actual number of parallel conductors.
• Size the tray on fill as well as on load: 1500 V DC cables have thicker insulation, so width calculations based on 1000 V cable diameters will come out short. Recalculate from the actual outer diameter.
• Provide expansion joints sized for the material and the 50 K swing — a 200 m straight run in steel moves by tens of millimetres — and place them at the structural break points as well.
• Where rodents are a confirmed problem, use covers at accessible sections but keep inspection hatches; do not cover the entire run without addressing the thermal derating that follows.
• Bond every tray section and maintain continuity across expansion joints with flexible jumpers, since the array’s equipotential bonding is part of the overall protection concept addressed in IEC 62548 and IEC 60364-7-712.

Common mistakes

• Specifying galvanised tray for a coastal or high-chloride site, then chasing coating failures within a few years.
• Running DC positive and negative conductors in separate trays or opposite sides of the site, increasing loop inductance.
• Sizing tray fill from 1000 V cable diameters on a 1500 V design.
• Bolting aluminium tray directly to stainless supports or copper bonding lugs without galvanic isolation.
• Omitting drip loops at combiner boxes, so moisture tracks into enclosures.
• Installing continuous covers across expansion joints and across structural movement points.
• Assuming the cable is UV-resistant because it is a “PV cable” — EN 50618 covers UV resistance of the cable, but any exposed tray accessories, ties and markers need their own rating.

Acceptance checkpoints

• Verify coating thickness on metallic tray against the specified system using an appropriate gauge method, and record results by batch.
• Check tray fill against the actual installed cable outer diameters, and record the calculation.
• Confirm the material certificate for stainless grades where specified.
• Measure and record bonding continuity across every joint and expansion device.
• Carry out the PV commissioning tests in IEC 62446-1 — including insulation resistance, polarity, open-circuit voltage and string current checks — and keep the results in the plant documentation file.
• Record expansion joint gap settings with installation temperature and photographs.

Selection Key Points

1. Establish the corrosivity category per ISO 9223 before choosing a material.
2. Choose ladder tray where heat dissipation governs, covered tray only where rodent or mechanical protection does.
3. Size fill from the real cable outer diameter at the system voltage.
4. Keep DC circuit conductors together; separate DC from instrumentation.
5. Calculate thermal movement and provide rated expansion devices.
6. Specify fixings and bonding hardware that are galvanically compatible with the tray.
7. Confirm UV performance for every polymer component, including covers, ties and markers.

Quality Inspection Points

• Material certificates and coating batch records for tray and fittings.
• Coating thickness measurement on a defined sampling basis, with results recorded.
• Dimensional check of tray width, rung spacing and thickness against the approved drawing.
• Load verification: confirm the tray system’s declared load class and support spacing per IEC 61537 classification and the manufacturer’s span data.
• Continuity and bonding checks across all joints.
• Visual check of cut edges, drilled holes and site modifications for corrosion protection reinstatement.

Supplier Evaluation

Ask for the IEC 61537 classification and declared load data with the corresponding support spacing, the coating specification with thickness range and applicable durability category, the material certificate route for stainless grades, UV exposure data for any FRP or polymer component, and the expansion device travel rating. For PV projects specifically, ask whether the supplier has supplied tray for a 1500 V DC installation, because the fill and spacing assumptions are materially different from a 1000 V design.

FAQ

1. Is galvanised steel tray adequate for a solar farm?

On inland sites at ISO 9223 C2 to C3, hot-dip galvanised tray to ISO 1461 is a common and economical choice. At C4 or C5 — coastal, high-chloride, or industrial atmospheres — specify stainless or a documented FRP system instead.

2. Should DC cables be covered or left open?

Open ladder tray dissipates heat better. Covers protect against rodents and UV but require a thermal derating check. Decide based on the site’s animal/mechanical risk, then confirm the ampacity with the cable manufacturer.

3. Why keep positive and negative conductors together?

To keep the loop area small. Separating them increases inductance, which worsens fault transients and can affect protection device behaviour.

4. Does IEC 61537 cover FRP tray?

IEC 61537 covers cable tray and ladder systems and their classification. FRP tray systems are also addressed by NEMA FG-1 in North America. Confirm which framework applies and ask for the manufacturer’s load, UV and fire performance data.

5. What commissioning tests apply to PV cabling?

IEC 62446-1 sets out the documentation, commissioning tests and inspection requirements for PV systems, including insulation resistance, polarity and string measurements.

6. How do I stop rodents damaging cables in tray?

Covers, closed conduits at vulnerable sections, and physical barriers at entry points. Where covers are used, apply the appropriate grouping correction for the reduced heat dissipation.

7. Do tray fixings need to match the tray material?

Yes. Dissimilar metals in contact form a galvanic couple; aluminium tray on stainless supports or with copper bonding lugs will corrode without isolation. Specify compatible fixings and isolation where metals differ.

Talk to BANGE About PV Cable Management

Send your plant layout, system voltage, cable schedule and site corrosivity assessment, and we will return a tray material and routing proposal with fill calculations and expansion provisions. Contact BANGE Electric to start the review.

Requirements may vary by application, market, and applicable standard.