DC Distribution Box | Accurate Engineers


DC Distribution Box

A DC distribution box will be mounted close to the solar grid inverter. The DC distribution box will be of the CRCA/MS thermo plastic IP65 DIN rail mounting type and shall comprise the following components and cable terminations:

Incoming 2 core (Positive and negative DC) cables from the DC Combiner Box;

DC circuit breaker, 2 pole (the cable from the DC Combiner Box will be connected to this circuit breaker on the incoming side);

DC surge protection device (SPD), class 2 as per IEC 60364-5-53;

Outgoing 2 core cable(Positive and negative DC) to the solar grid inverter.

As an alternative to the DC circuit breaker a DC isolator may be used inside the DC Distribution Box or in a separate external thermoplastic IP 65 enclosure adjacent to the DC Distribution Box. If a DC isolator is used instead of a DC circuit breaker, a DC fuse shall be installed inside the DC Distribution Box to protect the DC cable that runs from the DC Distribution Box to the Solar Grid Inverter.

DC and AC CABLES:

For the DC cabling, XLPE insulated and PVC sheathed, UV stabilized single core flexible copper cables shall be used. Multi-core cables shall not be used.

For the AC cabling, PVC or XLPE insulated and PVC sheathed single or multi- core flexible copper cables shall be used. Outdoor AC cables shall have a UV- stabilised outer sheath.

The total voltage drop on the cable segments from the solar PV modules to the solar grid inverter shall not exceed 2.0%.

The total voltage drop on the cable segments from the solar grid inverter to the building distribution board shall not exceed 2.0%

The DC cables from the SPV module array shall run through a UVstabilised
PVC conduit pipe of adequate diameter with a minimum wall thickness of 1.5mm.
Cables and wires used for the interconnection of solar PV modules shall be provided with solar PV connectors and couplers.

All cables and conduit pipes shall be clamped to the rooftop/ walls/parapet with thermo-plastic clamps at intervals not exceeding 50 cm.

The minimum DC cable size shall be 4.0 mm2 copper. The minimum AC cable size shall be 4.0 mm2 copper. In three phase systems, the size of the neutral wire size shall be equal to the size of the phase wires.

Cables and conduits that have to pass through walls or ceilings shall be taken through a PVC pipe sleeve.

Cable conductors shall be terminated with tinned copper end-ferrules to prevent

fraying and breaking of individual wire strands. The termination of the DC and

AC cables at the Solar Grid Inverter shall be done as per instructions of the

manufacturer, which in most cases will include the use of special connectors.

Only copper cables of appropriate size and of reputed-make shall have to be used. However aluminum cables can be used on A.C side.

  1. a)  All connections should be properly terminated, soldered and/or sealed from outdoor and indoor elements. Relevant codes and operating manuals must be followed. Extensive wiring and terminations (connection points) for all PV components is needed along with electrical connection to lighting loads.

  2. b)  All the Cu/Al. PVC or XLPE insulated Armored. Sheathed cables required for the plant will be provided by the manufacturer.

  3. c)  Only terminal cable joints shall be accepted. No cable joint to join two cable ends shall be accepted. All cable/wires shall be marked with good quality letter and number ferrules of proper sizes so that the cables can be identified easily.

    All Cables shall confirm relevant IS/ IEC standards

    All cables shall be supplied in the single largest length to restricting the straight

through joints to the minimum number.