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WEEB Equipment Grounding Strategy

Learn about the WEEB strategy for grounding PV equipment.

In recent years, the popularity of using the racking for PV modules as the equipment grounding system at the array has grown tremendously. Advances in module frames, and faster racking methods have pushed down costs of systems by decreasing parts and labor that was necessary for racking and grounding. Spearheading the movement towards washer-based monolithic grounding is the PV equipment company Wiley Electronics. Their product line for grounding are called WEEB (for Washer, Electrical Equipment Bond). Other manufacturers of racking equipment have bonding washer equipment available for use with their systems; they include:

  • Iron Ridge
  • Direct Power and Water
  • MT Solar
  • Tamarack Solar

The concept is that washers with teeth bite into the surfaces of both racking equipment and module frames that are both typically constructed of anodized aluminum. By placing the WEEB washer components between contact points of modules and racking equipment and appropriately torquing them, these washers bite into the aluminum at both sides providing a permanent electrical bond sufficient for array equipment grounding.

Since the PV industry product cycle moves very quickly and there is not any standardized frame for modules or standardized racking system, the WEEB product line is constantly adapting to the multiple racking and module choices available in the marketplace. Currently there are WEEBs available for 6 different racking manufacturers, and these can function with innumerable modules manufactured by dozens and dozens of PV producers.

From the integrator’s perspective, the dizzying array of choices can muddy the water when the time comes for equipment selection. The two sections of the code that can serve to clear this path are 690.43 Equipment Grounding and 110.3B Installation and Use of Equipment. Essentially these two sections specify that equipment used in the array must be listed for the application AND the integration of said equipment must be done in accordance to the instructions of the listed equipment in question.  This is where some of the problems can arise. Even when the grounding equipment (WEEBs in our case) are listed for the application, the modules, which also carry a listing and instructions, may not identify the equipment grounding technique using WEEBs as part of their instructions. This may be interpreted as a violation of 110.3B. Beyond the mere omission of identifying WEEBs as an accepted equipment grounding method, because of the physical realities of their frames, some modules must prohibit the use of WEEBs because the grooves, channels, or shapes on their frames prevent successful bonding through the use of WEEBs.

Generally we recommend following these 3 steps in order to ensure a compliant equipment grounding setup using WEEBs.

  1. Know the specific make and model of the modules that will be used for the rails
  2. Know the specific make and model of the racking system that will be utilized
  3. Given the module and racking setup, consult the Wiley Electronics page, and the module’s instructions to see what the appropriate parts are, if they are accepted by the manufacturer or not.