Solar DC Cable: H1Z2Z2-K, UL 4703, Sizing & RFQ Guide

■1) What Cable Is Suitable for Solar DC Installations?

PV modules, string combiner boxes and inverters need cable designed for long-term DC service outdoors. A suitable cable normally uses a flexible Class 5 stranded copper conductor, cross-linked insulation and a durable halogen-free outer layer. It must match the maximum system voltage, current, ambient temperature, routing method and local approval requirements.

For European and many international projects, an H1Z2Z2 K solar cable made to EN 50618 is a common specification. North American projects commonly require UL 4703 solar cable, also identified as PV Wire. A general-purpose building wire should not be substituted simply because its conductor area appears adequate.

■2) H1Z2Z2-K vs UL 4703 Solar Cable

The practical difference in H1Z2Z2 K vs UL 4703 is the certification framework and market in which the cable will be accepted. These are not interchangeable labels. The authority having jurisdiction, EPC specification, equipment approvals and product certificate determine the acceptable construction.

■3) Outdoor Solar Cable Construction

Cable construction is a complete material system. Conductor flexibility, insulation, outer layer and connector dimensions must work together and remain within the scope of the selected standard.

What cable jacket is suitable for outdoor solar installations?

Specify a tested, cross-linked, halogen-free compound with the UV, ozone, weather, flame and temperature performance required by the selected cable standard. “Outdoor rated” without a product designation, test standard and certificate scope is not sufficient.

■4) Solar String Cable Size

What conductor size is required for a solar string?

There is no universal size. A proper solar string cable size check starts with design current and protective-device rules, then applies ambient-temperature, grouping, installation and terminal-temperature derating. The final size must also satisfy voltage-drop limits, connector range and the minimum size required by the adopted code or standard.

Sizes such as 4, 6 and 10 mm² are common in string circuits, but frequency of use is not a design calculation. Long routes or strict loss targets may require a larger conductor.

■5) Solar Cable Voltage Drop

How do I calculate voltage drop in a solar cable?

For a preliminary two-conductor DC calculation, use the complete positive-and-negative loop:

A more accurate solar cable voltage drop check uses the manufacturer’s maximum conductor resistance corrected for operating temperature. Compare the result with the project’s permitted loss, and evaluate unequal routes, parallel strings and connector losses separately where relevant.

■6) Tinned vs Bare Copper Solar Cable

What is the difference between tinned and bare copper solar cable?

Both conduct electricity; the main practical difference is surface protection. A tinned copper solar cable coats individual strands with tin, helping resist surface oxidation during manufacturing, termination and humid service. Bare copper may be economical and electrically suitable when the certified product design and environment allow it.

Tinning does not compensate for poor sealing, incompatible connectors or damaged insulation. Compare conductor class, DC resistance, corrosion exposure, termination instructions and the actual product certificate—not conductor colour alone.

■7) Manufacturer Certificates & Evidence

What certificates should a solar cable manufacturer provide?

Request a current certificate or listing covering the exact manufacturer, factory, model, standard, voltage rating and size range offered. Verify the certificate number with the issuing body. A certification logo printed on a brochure does not prove that the quoted product is within scope.

• Model-specific technical data sheet and dimensional information.

• EN 50618/H1Z2Z2-K certificate or UL 4703 listing, as required by the project.

• Relevant flame, UV/weathering, ozone, thermal endurance, cold-bend and electrical test evidence.

• RoHS, REACH or other declarations when contractually required.

• Required management-system certificates, lot traceability and routine test records.

• Connector compatibility evidence and installation instructions for the selected interface.

■8) Solar Cable RFQ Checklist

How do I prepare a solar cable RFQ?

A useful solar cable RFQ separates measurable technical requirements from commercial delivery information so every manufacturer quotes the same scope.

• Application and routeSystem voltage, string current, one-way length, installation method, environment and destination market.

• Standard and ratingH1Z2Z2-K to EN 50618 or PV Wire to UL 4703, with required voltage and temperature ratings.

• Cable constructionConductor material, class and size; insulation and jacket; colour, nominal outside diameter and permitted tolerance.

• PerformancePermitted voltage drop plus required UV, weather, ozone, flame, low-temperature and halogen performance.

• Approval evidenceCertificate number and scope, data sheet, sample, routine tests, batch report and traceability.

• Commercial deliveryQuantity, cut lengths, drum or coil size, printing, labels, packing, Incoterm, destination and required date.

■9) Frequently Asked Questions