Grounding PV modules to reduce or eliminate shock and fire hazards is necessary and required by the National Electrical Code. The grounding guidelines of the Code essentially state that all electrical equipment is to be grounded by means of direct attachment to an equipment grounding conductor which is recognized by Section 250.118 of the code. This can be done in many different ways. The traditional method is to use the ground bond point of each solar panel and connect all the panels together with heavy gauge bare copper wire. This approach can be difficult, time-consuming and costly.
Some of the difficulties in grounding PV modules arise from the fact that copper conductors are typically used for electrical connections while the module frames are generally made of aluminum. The incompatibility of copper and aluminum was discovered from numerous fires in houses wired with aluminum wiring in the 1970’s. Copper an aluminum will also react and corrode through galvanic action. The surfaces of aluminum frames either are naturally oxidized, anodized or have clear coatings, any of which constitute an insulating surface. These insulating barriers do not provide any protection from electrical shocks, but are sufficient to impair long-lasting, low-resistance electrical connections. In order to use the bare copper wire for bonding, the fasteners attaching to the aluminum must be stainless steel.
Several years ago Wiley Electronics LLC developed a scheme that allows PV panels to be directly ground bonded to the aluminum rails or other mounting systems. The rails are then connected to each other and to ground. The products are marketed under the “WEEB” name. WEEB stands for "Washer, Electrical Equipment Bonding". The product line of WEEB parts include special washers with sharp ridges on them that penetrate through the non-conductive coatings of the aluminum module frames and mounting racks. The mounts themselves are then grounded so the entire assembly is grounded. The WEEB family consists of six products: WEEB-9.5, WEEB-DMC, WEEB-PMC, WEEB-SMC, WEEB-UMC, and WEEBLug.
The WEEB-9.5 is used for bonding modules to ground and pole mount systems. The WEEBLug provides a connection to the mounting system and has lay-in provision for an equipment ground conductor. The other WEEB products are used for rail mount systems and are individually configured for specific systems including those of most leading manufacturers (ProSolar, AEE, UniRac, Direct Power & Water, IronRidge, Schüco, etc.).
The WEEB system has gained wide popularity because it saves time in installations by eliminating the need for a separate ground wire to every PV module, it has been demonstrated to meet strict safety standards, and it has been shown to provide a reliable electrical connection that is gas-tight and therefore resistant to oxidation. WEEB products provide a relatively simple solution to a complicated issue in PV installations.
How do I know which WEEB from Wiley to use with which module or racking system? The following compatibility list gives you the answers.