Mid clamp

The mid clamp is the small metal part that holds tight, at the same time, the edges of two neighbouring panels placed on the same bar. Its body goes between the two frames, and when a single bolt is tightened both panels stay fixed. It is the part most often used on a roof, because every gap between two panels needs one.

The width of the clamp automatically sets the distance between panels as well, usually 18-22 mm, and that gap is not a fitting oversight: it is needed so that the frames can expand in the summer heat and so that water or melted snow can drain between the modules. The clamp is chosen according to the frame height of your panel, the most widespread versions being for frames of 30, 35 and 40 mm, to which the universal versions with an adjustable range are added. The bolt is tightened to the torque indicated by the module manufacturer, typically 8-14 Nm for M8; too loose, and the panel can move over time, too tight, and the frame deforms. The aluminium of the clamp and the stainless steel of the bolt do not corrode in contact with the module frame, so the assembly requires no later maintenance.

Body of extruded aluminium, M8 bolt with hammer or hexagonal head of A2 stainless steel and nut or locking plate that rotates in the rail channel. The distance between modules is determined by construction by the width of the clamp, usually 18-22 mm, and the frame heights served are usually 30-40 mm, depending on the version. The number of clamps and the permitted clamping zones on the frame are established according to the module manufacturer's mounting instructions, compliance with them being a condition for keeping the module warranty.

Who it suits

Suited to any installation with aluminium-framed modules mounted in a row on rails, whether we are talking about a pitched roof, a flat roof or a ground structure.

Terms explained

• Tightening torque (Nm): How tightly the bolt is tightened, measured with a torque wrench; the value is indicated by the panel manufacturer.
• Hammer-head bolt: A bolt with a rectangular head, which is inserted into the rail channel and locks with a quarter turn.
• Thermal expansion: The increase in size of metal when hot; that is why the panels are mounted with a small gap between them.

Technical specifications

Recommended applications

• Fixing the modules inside the row on aluminium rails
• Mounting on pitched roofs, flat roofs and ground structures
• Installations with aluminium-framed modules of standard height
• Systems where fast mounting is wanted, with a single tightening for two modules

Technical details

Generic product — standard specifications

The mid clamp is the element that simultaneously fixes the frames of two neighbouring photovoltaic modules, placed on the same mounting rail. The body of the clamp rests between the two frames and takes up, through the tightening of a single bolt, both the vertical clamping pressure and the constant spacing between modules (usually 18-22 mm, a gap needed for the thermal expansion of the frames and for water drainage).

The standard construction comprises a body of extruded aluminium, a hammer-head or hexagonal-head M8 bolt of A2 stainless steel and the nut/locking plate that rotate in the rail channel. The stainless materials and the aluminium ensure galvanic compatibility with the aluminium frame of the module and with the rail, and tightening to the torque indicated by the module manufacturer (typically 8-14 Nm for M8 bolts) guarantees that the clamping force is maintained over time.

Mid clamps are produced for specific frame heights, the most widespread being the versions for 30, 35 and 40 mm, respectively universal clamps with an adjustable range. The number of clamps is established according to the module manufacturer's mounting instructions, which also indicate the permitted clamping zones on the frame, essential for keeping the module warranty.