The rated ampacity of 4mm² H1Z2Z2-K solar cable is 55 A for a single cable in free air at up to 60°C ambient (EN 50618, Annex A). On a surface it is 52 A, and two loaded cables touching on a surface are rated 44 A each.
A PV string usually draws 10–15 A, so 4mm² almost always has enough current capacity. On long runs, voltage drop — not ampacity — is what pushes you to 6mm². This page is the ampacity reference; for the size choice see the 4mm² vs 6mm² comparison, and for voltage drop use the cable size calculator.
Why you may have seen 32 A for 4mm²
Around 32 A is a figure from general building-wiring tables (IEC 60364-5-52) for PVC-insulated cable rated 70°C. H1Z2Z2-K is a solar cable with cross-linked insulation rated for a 120°C conductor, and its own standard, EN 50618, gives the higher ratings shown in the table below. Use the cable datasheet ratings, then apply your local installation rules.
Derating: hot roofs and grouped cables
The EN 50618 ratings already assume an ambient temperature of up to 60°C. Above that, the datasheet factors are 0.92 at 70°C, 0.84 at 80°C and 0.75 at 90°C. Grouping also lowers the rating — the table shows two touching cables on a surface. For conduit, trays with many cables, or buried runs, use the factors in your local code (for example AS/NZS 3008 / 5033 or NEC 690 and 310).
- Ambient above 60°C: apply 0.92 (70°C), 0.84 (80°C) or 0.75 (90°C)
- Two or more touching cables: use the grouped rating, not the free-air one
- US projects: NEC sizes PV circuits at 1.56 × Isc; use UL 4703 PV Wire ratings
- Even after derating, 4mm² usually covers a 10–15 A string with margin
Voltage drop and certificates
Ampacity is a safety limit; voltage drop is an efficiency limit. On long runs voltage drop forces an upsize long before ampacity does, so check both. On certificates, specify the standard for the destination market — EN 50618 / IEC 62930 for EU/IEC, UL 4703 for the USA — and confirm jacket marking and reel length before order.
H1Z2Z2-K current rating by size (EN 50618, ambient up to 60°C)
| Cable size | Single cable, free air | Single cable, on a surface | Two cables touching, on a surface |
|---|---|---|---|
| 2.5 mm² | 41 A | 39 A | 33 A |
| 4 mm² | 55 A | 52 A | 44 A |
| 6 mm² | 70 A | 67 A | 57 A |
| 10 mm² | 98 A | 93 A | 79 A |
Values from EN 50618 Annex A as published in H1Z2Z2-K datasheets (conductor 120°C). Ambient factors above 60°C: 0.92 at 70°C, 0.84 at 80°C, 0.75 at 90°C. Local installation codes may add further factors — confirm with the actual cable datasheet and your code before specifying.
Procurement decision table
| Decision area | Buyer question | Procurement check | Risk control |
|---|---|---|---|
| Product scope | Which product families does this cover? | PV Cables, H1Z2Z2-K Solar Cable | Using general building-wiring tables instead of the PV cable datasheet |
| Specification input | What must be stated before comparing quotes? | Module Isc (and × 1.25 for fuse, × 1.56 under NEC) | Use the same specification wording across supplier quotes. |
| Commercial input | What makes the quote operationally useful? | Ambient temperature at the cable route | Tie quantity, packing and destination to the same RFQ line. |
| Quality gate | What should be checked before shipment? | 4mm² vs 6mm² Solar Cable | Ignoring ambient temperature above 60°C |
BOM and RFQ context
4mm² PV Cable Ampacity: 55A Rating, Derating & Table is most useful when it is read as a sourcing decision, not only an informational article. The affected product scope normally includes PV Cables, H1Z2Z2-K Solar Cable. A buyer should connect the answer to a live BOM, because cable size, connector rating, protection device choice, box configuration, storage accessories and export packing can change together.
For a procurement guide, the goal is to turn a broad buying question into a repeatable RFQ structure. The buyer should leave with the required product family, specification fields, quality checks and internal links needed to continue into the central products hub. In an RFQ, the minimum inputs should include Module Isc (and × 1.25 for fuse, × 1.56 under NEC), Ambient temperature at the cable route, Installation method (free air / surface / conduit / buried), Number of grouped cables. These inputs let a sourcing team compare suppliers on the same basis instead of only comparing unit price.
The related follow-up content is 4mm² vs 6mm² Solar Cable, PV Cable Sizing Guide, BOS 1500V Selection Guide. Use those pages to validate standards, sizing, inspection and packing before sending a final quote request. The main risk to avoid is: Using general building-wiring tables instead of the PV cable datasheet Ignoring ambient temperature above 60°C
FAQ
What is the ampacity of 4mm² solar cable?
55 A for a single 4mm² H1Z2Z2-K cable in free air at up to 60°C ambient, 52 A on a surface, and 44 A each for two touching cables on a surface (EN 50618). Above 60°C ambient apply 0.92 at 70°C, 0.84 at 80°C and 0.75 at 90°C.
Is 4mm² enough for my PV string?
For current, almost always: a typical string draws 10–15 A and 4mm² is rated well above that even after derating. The real check is voltage drop on long runs, which often pushes the choice to 6mm².
What is the ampacity of 6mm² and 10mm² PV cable?
Per EN 50618, 6mm² H1Z2Z2-K is rated 70 A in free air (67 A on a surface, 57 A for two touching cables) and 10mm² is rated 98 A (93 A / 79 A), at up to 60°C ambient.
When should I use 6mm² instead of 4mm²?
Mostly for voltage drop: long one-way runs (over about 25–30 m), higher-current modules, or when the design target is 1% or lower. See the 4mm² vs 6mm² comparison and the cable size calculator.