Middle clamps - Central connecting elements in photovoltaic installation
Middle clamps are indispensable components in photovoltaic assembly and are used to securely attach the solar modules to the substructure. They are used as connecting elements between two adjacent modules and must meet the highest requirements for stability and durability.
Construction and material of middle clamps
The basic construction of a center clamp typically consists of a clamp body made of high-quality aluminum, which is protected against corrosion by anodization. The clamping surfaces are occasionally equipped with EPDM rubber inserts (ethylene propylene diene rubber), which ensure optimal hold and at the same time protect the sensitive module frames from damage. The clamping is usually done using a stainless steel screw with a self-locking thread, which prevents accidental loosening.
Technical specifications
The height of the middle clamps must be exactly matched to the module frames used, which are typically between 30 and 55 millimeters thick. The clamping force is achieved by a defined tightening torque, which is between 8 and 15 Newton meters depending on the manufacturer. Modern systems have torque indicators that ensure optimal installation.
Modern center clamps combine several functions in one component. In addition to the primary fastening function, they take over the electrical potential equalization between the module frame and the substructure using integrated earthing tips or springs. This functional integration not only saves time during assembly, but also increases the operational reliability of the entire system.
Assembly types
During assembly, a distinction is made between different systems:
- Hammer head screw systems for lateral insertion into mounting rails
- Click systems for pre-assembly with minimal tools
- Classic screw systems with direct screwing
- Special systems for frameless modules
Quality assurance and testing
The quality of the center clamps is ensured by extensive testing. These include:
- Tensile strength tests under different temperature conditions
- Salt spray tests to check corrosion resistance
- Vibration tests to simulate wind loads
- UV resistance tests of EPDM components
- Electrical conductivity tests for terminals with earthing function
Other aspects
Proper installation requires special care, as the middle terminals are largely responsible for the stability of the modules. The specified tightening torque must be adhered to precisely in order to ensure secure fastening and to avoid damage to the module frame. Regular checking of the tight fit as part of system maintenance is recommended.
The development of modern center clamps aims to further simplify assembly while increasing functionality. New systems enable tool-free assembly using click mechanisms or have integrated cable guides. The use of new materials such as carbon fiber reinforced plastics is also being tested to reduce weight and improve handling.
The number and position of the middle clamps must be carefully planned. The manufacturer's specifications of the module manufacturers must be observed, as these define the permissible clamping zones and minimum clamping forces. Modern planning tools support the correct positioning and dimensioning of the clamps, taking into account all relevant parameters such as wind load, snow load and module size.
The correct selection and installation of center clamps is crucial for the long-term safety of a photovoltaic system. They must perform their function reliably over the entire service life of the system of 20-30 years and withstand the diverse environmental influences.