Created by: Glen Zhu | Updated Date: June 5th, 2024
The solar combiner box is a wiring device that ensures solar modules’ orderly connection and current collection function. This device can ensure that the solar system is easy to cut off during maintenance and inspection, reducing the scope of power outages when faults occur in the solar system.
Before starting the installation process, let’s first familiarize ourselves with the main components of the combiner box:
Enclosure: The enclosure of the solar combiner box is typically made of metal or plastic and is designed to protect internal components from environmental factors such as rain, dust, and sunlight.
Fuse holder or circuit breaker: These components are used to protect each string of solar panels from overcurrent situations. They serve as safety devices to prevent potential damage to the system.
Busbar or terminal block: Busbars or terminal blocks are used to connect positive and negative cables from the strings of solar panels. They provide a safe and orderly way to terminate cables.
Ground busbar: The ground busbar is used to connect equipment grounding conductors from the strings of solar panels, ensuring proper grounding of the system.
Cable entry device or conduit entry port: These openings allow cables from the strings of solar panels and output cables to enter the combiner box while maintaining waterproof sealing.
Installation tools and parts
Name | Function | Name | Function | Name | Function |
One-word screwdriver | Fastening screws | Cross screwdriver | Fastening screws | Wrench | Fastening bolt |
Torque wrench | Fastening expansion bolt | Diagonal pliers | Trimming buckle | Wire stripper pliers | Peel off the outer sheath of the cable. |
Hydraulic pliers | Press-fit copper nose clip | Electric drill | Drilling hole | Glove | Wear during installation. |
Electrical screwdriver | Fastening screws |
Wiring diagram
How are the components of the photovoltaic combiner box installed? Taking a 4 String Input 2 String Output solar combiner box as an example, let’s explain in detail through the video below.
Pre-installation inspection
Before installing the solar combiner box, an inspection should be carried out to prevent possible damage during transportation. If any damage is detected, please get in touch with the transportation company or product provider and take photos for verification.
Installation tools and parts
Name | Function | Name | Function | Name | Function |
One-word screwdriver | Fastening screws | Cross screwdriver | Fastening screws | Wrench | Fastening bolt |
Torque wrench | Fastening expansion bolt | Diagonal pliers | Trimming buckle | Wire stripper pliers | Peel off the outer sheath of the cable. |
Hydraulic pliers | Press-fit copper nose clip | Electric drill | drilling hole | tape measure | Measure distance |
Carpenter’s square | Measure distance | Level ruler | Check if it is level. | Plumb line measuring instrument | Check vertical deviation. |
Buckle | Bind cables | Glove | Wear during installation. | Insulation tape | Bandage exposed wire. |
Multimeter | Measure resistance, voltage, and current. | Electrical screwdriver | Fastening screws |
Mechanical Installation Basic Requirements
1. External dimensions
2. PV combiner box mechanical installation precautions
2.2 The general cooling method for PV combiner boxes is natural cooling. To ensure the normal operation and service life of the combiner box, try not to install it in areas with direct sunlight or excessively high ambient temperatures.
2.3 Please ensure that the solar combiner box installed on the wall or pillar has sufficient strength to bear its weight.
2.4 Outdoor installed solar combiner boxes should not be opened during rainy or snowy weather!
2.5 When installing solar arrays during the day, use opaque materials to cover the solar panels. Otherwise, under sunlight, the solar panels will generate high voltage, which may lead to electric shock hazards.
2.6 The entry and exit holes of the box should be tightly sealed to prevent small animals from entering and causing short circuits inside the box.
The installation method of the solar combiner box can be chosen according to the actual situation of the work site, usually using wall-mounted, pole-hugging, and ground-mounted.
Wall-mounted: It is recommended to use expansion screws to fix it on the wall through the mounting holes on both sides of the solar combiner box.
Pole-hugging: It is recommended to use clamps and angle steel as support brackets, and install the combiner box on them with screws.
Electrical Wiring and Steps
1.4 Before installing the solar combiner box, perform insulation testing on its internal components using a megohmmeter.
1.5 The arrangement and spacing of components inside the box should comply with relevant regulations to ensure the debugging, operation, maintenance, repair, and safe operation requirements.
1.6 Both input and output must not be reversed, otherwise the subsequent equipment may not work properly or even damage other devices.
1.7 After connecting the solar lightning protection junction box to the solar power generation system according to the principle and installation wiring diagram, it should be reliably connected to the grounding end of the lightning protection box with a lightning protection ground wire or busbar. The connecting wires should be as short and straight as possible, with a cross-sectional area of not less than 16 square millimeters. The grounding resistance value should not exceed 4 ohms; otherwise, rectification of the grounding grid should be carried out to ensure lightning protection effectiveness.
1.8 When making external connections, please ensure that screws are tightened to prevent loose connections from overheating and burning. Ensure that waterproof terminals are tightened to avoid water leakage causing faults in the solar junction box.
1.9 Paste a non-fading system diagram and necessary secondary wiring diagrams firmly on the box or the cabinet door.
1.10 Wiring requirements include using flame-retardant cables arranged neatly and aesthetically pleasingly installed securely; wires connected to configured electrical appliances must meet crimping and soldering requirements; externally used heat shrinkable tubes must be tightly fitted to ensure good contact.
The solar combiner box’s input and output, communication, grounding, and other external interfaces are located at the bottom of the enclosure.
The specific number of input channels is determined by the model used. Note that the wires connected to the positive terminal of the solar module output are on the left side at the bottom, while those connected to the negative terminal of the solar module output are on the right side at the bottom.
The outputs include the direct current positive pole after combining, the direct current negative pole, and the ground; where the ground wire is yellow-green.
When the current monitoring module detects a sudden change in the current of a certain branch, it will first issue an alarm, then delay driving the tripping unit to trip and open the circuit breaker. Considering cost factors, this may not need to be added.
Users can refer to the table below to select suitable cables for different terminals.
| Terminal Description | Terminal size | The use of cable outer diameter | Recommended wiring | |
| Route 8 | Route 16 | |||
| DC positive input | PG9-09G | 4.5-8mm | 4-6mm | |
| DC negative input | PG9-09G | 4.5-8mm | 4-6mm | |
| Direct current positive pole confluence output | PG21-18G | 10-18mm | 35mm | 70mm |
| Direct current negative pole busbar output | PG21-18G | 10-18mm | 35mm | 70mm |
| Ground terminal | PG11-10G | 6-10mm | 16mm | |
| Communication terminal | PG16-14G | 8.5-14mm | 1.5mm low resistance four-core shielded twisted pair cable | |
Commissioning of Solar Combiner Box
The solar combiner box will automatically run when powered on and stop when power is off. The DC output of the combiner box can be shut down through the internal circuit breaker. The following requirements should be met before commissioning:
4. Only after all checks are passed can it be energized for trial operation.
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