PV Combiner Box Cable Glands: Match Cable Diameter and Keep the Seal

A solar combiner box may have a suitable enclosure IP rating and still leak after cable entries are added. The gland must seal around the actual cable jacket and at the enclosure wall. Choosing it by thread size alone is insufficient. This guide explains what to request and verify before installation.

Quick answer

Match the gland’s documented sealing range to the outside diameter of the specific cable. Then check the mounting thread, wall thickness, gasket, material, environmental rating and installation instructions. A gland’s own IP marking does not automatically give the completed combiner box the same rating.

Three dimensions that are easy to confuse

• Thread size: the entry and mating thread in the enclosure, such as M20 × 1.5. It does not state which cable diameter will seal.
• Cable outside diameter: the measured diameter over the jacket, not the conductor cross-section printed on a drawing.
• Sealing range: the gland manufacturer’s permitted cable diameter interval for the exact part number.

For a manufacturer example, Phoenix Contact part 1415192 has an M20 × 1.5 thread and a documented external cable diameter range of 6–13 mm. Those figures apply to that part only; they are not a universal M20 specification or a recommendation for every PV cable.

Why the correct gland matters in a PV combiner

String conductors, output cables and monitoring wires may have different outside diameters. A single gland model may not fit all of them. A cable below the seal’s specified range can leave a water path; one above it may prevent the gland from closing as designed. Incorrect assembly can also compromise strain relief.

IEC 60529 classifies enclosure protection against access, solids and water under defined tests. It does not certify every field-drilled entry in an assembled box. The finished assembly must account for the actual glands, plugs, connectors and cable entries.

Six checks before ordering or installing

1. List every entry. Count PV string, output, PE and signal cables separately; identify unused openings.
2. Record each cable. Obtain its outside-diameter tolerance and jacket material. Do not substitute conductor area for jacket diameter.
3. Match each diameter to a documented range. Check the exact gland ordering code. Rittal’s datasheet illustrates how thread sizes and clamping ranges are specified separately.
4. Check the enclosure interface. Confirm thread or hole size, wall thickness, washer or O-ring, locknut and supplier instructions.
5. 환경을 확인합니다. Assess outdoor exposure, UV, corrosion, temperature and the required rating for the complete assembly.
6. Verify installation. Follow manufacturer assembly and torque instructions where provided. Check for jacket damage, uneven compression and water tracks.

What to include in a combiner-box RFQ

Give the supplier an entry schedule: cable count and purpose, each outside-diameter range, entry position, required gland material and site environment. Ask for exact gland and blanking-plug part numbers, an entry layout and the finished enclosure’s documented protection. This is more useful than asking only for “IP65 cable glands.”

For broader context, see our custom combiner-box RFQ guide, IP rating comparison, condensation troubleshooting guide 및 combiner protection guide. Send KUANGYA the entry schedule for project-specific component review.

자주 묻는 질문

Is M20 enough to choose a cable gland?

No. M20 identifies the entry thread. The exact gland also needs a sealing range that covers the actual cable outside diameter.

Can one gland seal two PV cables?

Only if the manufacturer approves that exact gland and insert for two cables of the relevant diameters. Do not put two cables through a standard single-cable seal by assumption.

Does an IP68 gland make the combiner box IP68?

No. The assembled rating also depends on the enclosure, door seals, all other entries and installation conditions.

안전: Qualified personnel should inspect or modify PV DC equipment under an approved isolation procedure. PV conductors can remain energized in daylight. Never alter an energized combiner box to investigate a leak.