Cable & breaker sizing — 50 kW three-phase off-grid

A reference walk-through of how the cable and breaker spec falls out for a 50 kW three-phase Deye hybrid (SUN-50K-SG01HP3-AU-BM4) on an off-grid site. Use it as a sanity-check framework — not a substitute for a designed BOM signed off by a licensed electrician.

Why off-grid sizing is different

The inverter has an off-grid peak power mode — 2× rated for up to 10 s (datasheet “Peak Power, off-grid”). That brief surge, not the continuous rating, drives the DC battery breaker size.

Battery DC protection — depends on the battery

• GE-F60 (outdoor cabinet): the integrated PDU has a built-in DC breaker, so generally no external DC breaker is needed; cables are supplied with the cabinet.
• BOS-G (indoor rack): rated IP20, so for the AU market an external DC overcurrent + isolation device (both poles) is required. A 200 A DC breaker is the typical spec — at ~400 V battery voltage the 10 s peak can briefly reach ~187 A, so a 125/160 A device would trip. Cable (commonly 4 AWG × 2) ships with the battery package.

AC ports — GRID and GEN are mutually exclusive

A Deye hybrid uses either the grid or a generator as its input source — not both at once. The 240 A AC spec in the manual applies to whichever input (GRID or GEN) is connected, because both carry the same max continuous passthrough current.

Port	Pure battery + PV (no genset)	With diesel genset backup
GRID	not used	not used (off-grid)
GEN	not used	240 A 3P + 95 mm² (4/0 AWG)
LOAD	125 A 3P + 25 mm² (2 AWG)	125 A 3P + 25 mm² (2 AWG)

The LOAD port is sized to the inverter’s own output: off-grid sustained ≈ 110 % rated (~80 A/phase continuous for a 50 K), with brief peaks to ~108 A/phase during 10 s peak events.

PV strings

• PV cable 2.5–4 mm² is sufficient — per-string operating current is ~18 A.
• Connectors are Stäubli D4 (often called “MC4”); 2.5 mm² with a D4 is rated 22.5 A per IEC 62852.
• Using 4 mm² (6 mm² on long runs) is fine — it exceeds the manual without violating it.

Earthing

Earth tracks the active conductor on each port:

• LOAD (25 mm² active) → 16 mm² (4 AWG) earth
• GEN (95 mm² active) → 50 mm² (0 AWG) earth

Per-inverter BOM (template)

• 1 × SUN-50K-SG01HP3-AU-BM4
• PV: 2.5–4 mm² PV1-F + D4 connectors (matched crimps)
• LOAD port: 125 A 3P breaker + 25 mm² (2 AWG) + 16 mm² (4 AWG) earth
• GRID port: nothing (off-grid)
• Battery DC: GE-F60 → none external; BOS-G → 200 A DC breaker + isolation per input, 4 AWG × 2
• GEN port (only if genset): 240 A 3P + 95 mm² + 50 mm² earth

Indicative only. Size every conductor and protective device to AS/NZS 3000 / 3008.1 / 5139 for the actual installation, allow for grouping/temperature derating, and have a licensed electrician verify. When in doubt, call Suncloud and we’ll work through the BOM with you.