WILEY
ELECTRONICS LLC.
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NEC Considerations
The WEEB meets code requirements. Here is why.
- The WEEB devices provide a low impedance electrical connection between a PV module and its mounting frame. When the mounting frame is also grounded, then the PV module is also grounded. This is described in the 2005 NEC section 250.136 which states:
Under the conditions specified in 250.136(A) and (B), the non-current-carrying parts of the equipment shall be considered effectively grounded.
- (A) Equipment Secured to Grounded Metal Supports
- Electrical equipment secured to and in electrical contact with a metal rack or structure provided for its support and grounded by one of the means indicated in 250.134.
This will be made more explicit in the 2008 NEC. The following are part of the 2008 NEC proposed changes. Salient portions are shown highlighted.
690.43 Equipment Grounding (Revised)
Proposal: Add a second and third paragraph to the existing section as follows: Devices listed and identified for grounding the metallic frames of PV modules are permitted to ground the exposed metallic frames of PV modules to grounded mounting structures. Devices identified and listed for bonding the metallic frames of PV modules are permitted to bond the exposed metallic frames of PV modules to the metallic frames of adjacent PV modules.
Equipment-grounding conductors for the PV array and structure (when required) shall be contained within the same raceway or cable, or otherwise run with the PV array circuit conductors when those circuit conductors leave the vicinity of the PV array.
Substantiation: The proposed second paragraph is added because module grounding clips and other devices are being developed and listed that will effectively penetrate the oxide or anodizing on aluminum framed PV modules and ground them to grounded PV array mounting structures or effectively bond them to adjacent PV modules which, in turn, may be grounded. The existing grounding and bonding requirements in Sections 250.134 or 250.136 do not specifically or generally allow the use of such devices. Nor do they prohibit the use of such devices. Clarification is needed in Article 690.
Does code allow the mounting structure to be used as a conductor?
According to the NEC, Section 250.118, the equipment grounding conductor may be "aluminum ... in the form of ... a busbar of any shape", which would certainly describe any of the commercially available aluminum mounting structures.
As an example, the ProSolar RoofTrac has a cross-sectional area of 263 square mm, which is equivalent to approximately twenty wires of 6 AWG. The material is structural grade aluminum manufactured to ASTM standards and therefore will be consistently of high quality material. This will make a very good conductor indeed!
Are WEEB devices compatible with all modules?
All modules may be used with the following exceptions:
Don't module manufacturer have to list WEEB devices in their installation instructions?
No. This is a common misconception. PV module manufacturers are required to specify how their products are grounded, but do not have to list every manufacturer of grounding devices. Like all listed devices, WEEBs should be used according to Wiley Electronics LLC installation instructions which specify module as well as mount manufacturer compatibility.
Some module manufacturers installation instructions already cover the WEEB in a general way or have provided technical bulletins to avoid confusion.
Why aren't the WEEBs listed to UL1703?
UL1703 is the standard for Flat-Plate Photovoltaic Modules and Panels. While module manufacturers may include grounding equipment with their modules, there is no requirement in the standard to do so. There are also no requirements which apply to grounding equipment alone and so the WEEB products cannot be properly listed to this standard. If and when requirements are added to the standard to allow listing of grounding equipment , Wiley Electronics LLC will have its listings updated.
What about the recent UL "significant interpretation" to UL1703?
Recently UL has begun requiring module makers to submit grounding equipment and mouting racks with modules to be listed. Other NRTLs strictly follow the UL1703 standard and do not have these requirements. We believe these new requirements to be improper and so have filed a formal complaint with the American National Standards Institute (ANSI), the organization which gives UL the authority to develop standards. Please see the file, ANSI complaint.pdf, for details.