Suntree 20A 1000V DC Fuse Link with 1 Pole Holder
The Suntree SGR Series is a complete DC fuse assembly comprising a 20A cylindrical fuse link and a single-pole DIN rail-mounted holder, sold as a matched unit. It is rated at 1000V DC and purpose-built for photovoltaic string protection in solar PV systems. The assembly mounts directly onto a standard TH35 DIN rail, making it a straightforward fit inside DC combiner boxes, distribution boards, and solar electrical enclosures without additional wiring hardware.
The SGR series is manufactured by Suntree Electric Group (Zhejiang, China) and certified to IEC 60269-6 — the international standard specifically governing fuses for use in PV systems. The combination of fuse link and holder in a single SKU simplifies procurement and ensures dimensional compatibility between the two components from the factory.
The Fuse Link — 10×38mm DC-Rated Cylinder
The fuse element within the SGR assembly follows the universal 10×38mm cylindrical form factor. This is the global standard for solar string fuses and ensures the link is interchangeable with compatible holders across brands and combiner box manufacturers.
The 20A fuse link uses a silver or silver-alloy melt element — a material chosen for its predictable fusing characteristics and consistent I²t performance across the operating temperature range. The element is enclosed in a high-strength ceramic tube filled with chemically processed high-purity quartz sand, which acts as the arc-quenching medium under DC fault conditions. When a fault occurs, the quartz sand absorbs and disperses arc energy, preventing re-strike and containing the interruption inside the fuse body.
This construction delivers a short-circuit breaking capacity of 33,000A (33kA) at 1000V DC, tested at a time constant of 1–3ms. That figure covers the high prospective fault currents that can arise when multiple parallel strings contribute to a single fault point — a scenario that AC-rated fuses are not designed to handle safely.
The Holder — IP20 Single-Pole DIN Rail Mount
The SGR holder is a single-pole (1P) DIN rail-mounted fuse base with an IP20 ingress protection rating. IP20 indicates protection against solid objects larger than 12mm — sufficient for installation inside enclosed combiner boxes and distribution panels where fingers and tools are the primary contact risk.
The holder accepts the 10×38mm fuse link via a tool-free or minimal-tool extraction and insertion process. It snaps directly onto a standard TH35 (35mm wide) DIN rail without screws or brackets. The terminal connection accepts wire cross-sections of 2.5mm² to 10mm², covering the cable sizes commonly used in residential and commercial PV string wiring.
The holder body dimensions are 18mm (W) × 89mm (H) × 90mm (L), and the unit weighs 0.07kg. The compact 18mm width allows multiple SGR holders to be mounted side by side in a combiner box without excessive space consumption — important in installations with four to twelve parallel strings.
Fault Protection in PV String Arrays
The SGR 20A fuse link is suited to solar panel strings where the short-circuit current (Isc) per string falls within the range of approximately 10A to 12A. Standard IEC and NEC guidelines recommend fuse ratings not exceeding 2× Isc for string protection. A 20A fuse accordingly provides correct overcurrent protection for strings built from panels with Isc values in that range — which includes most 350W–550W monocrystalline panels wired at standard string voltages.
The SGR protects against three primary fault types:
- Reverse current faults — a shaded, damaged, or failed string in a parallel array can receive backfeed current from the remaining healthy strings. The fuse in the affected string clears the fault before reverse current damages the panels or wiring.
- Short-circuit faults — insulation breakdown, connector failure, or wiring damage can produce low-impedance faults. The 33kA breaking capacity ensures reliable interruption even when multiple parallel strings contribute to the fault current.
- Sustained overcurrents — prolonged overcurrents that fall below the short-circuit threshold are handled by the fuse’s thermal I²t characteristic. The higher the overcurrent, the faster the fuse operates, disconnecting the affected string before damage accumulates.
Installation Notes
The SGR mounts on a TH35 (DIN35) DIN rail inside a DC combiner box or distribution enclosure. One SGR unit is installed per string positive conductor in a parallel array. The holder’s 2.5–10mm² terminal range covers standard 4mm² and 6mm² PV cable commonly used for string runs in Kenya. The –30°C to +70°C operating temperature range ensures reliable performance in both highland and coastal Kenyan climates, as well as equatorial ambient conditions without thermal derating.
The SGR does not require any additional mounting hardware beyond the DIN rail. Wiring is completed at the screw terminals on each side of the holder.
Who Is This Best Suited For?
- Solar installers wiring multi-string parallel arrays into DC combiner boxes. The SGR provides a certified, matched fuse-and-holder unit in a single item, streamlining the bill of materials for combiner box builds. The 18mm width allows compact multi-way layouts.
- System integrators and EPC contractors specifying grid-tied solar installations. The IEC 60269-6 certification and 33kA breaking capacity meet the protection requirements for professionally certified PV systems in Kenya and internationally.
- Off-grid system builders connecting parallel strings to MPPT charge controllers. String-level fusing is required when more than two strings are paralleled; the SGR 20A is appropriately rated for most 350W–550W panels in such configurations.
- Panel installers standardising on DIN rail enclosures. The SGR’s DIN rail snap-fit and compact profile make it compatible with virtually all commercially available DC combiner boxes and solar distribution boards without modification.
- Technicians replacing failed holders or fuse assemblies. The matched SGR assembly ensures like-for-like replacement with verified dimensional and electrical compatibility, removing the risk of mismatched contact resistance from mixing brands.
