38, while cables with large specifications and special performance requirements (such as weather resistance, flame retardancy) are more expensive. For EPCs and installers bidding on 50–200kW commercial rooftop projects, the combiner box specification is a decisive factor for both system safety and project margin. The challenge is universal: how to meet stringent IEC requirements without over-specifying components that erode profitability? The. And the photovoltaic combiner box, as a key supporting device in the photovoltaic power generation system, can combine multiple photovoltaic components together, reduce the number of lines entering the inverter, simplify the system structure and provide various protection functions. For systems with three or more DC strings, using a solar combiner box is recommended according to international PV safety standards such as IEC 60364-7-712 for electrical installations of photovoltaic systems and IEC 61439-2 for low-voltage switchgear and controlgear assemblies. Consequently, a series of construction issues arise, including loosely connected wire harnesses, reversed wire harness connections, non-insulated cables, and string connections of components exceeding the design range.
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