PV Racks with Integrated Equipment Grounding


Inside this Article

Grounding with piercing clips
Where’s the ground wire? Module frames and racks, electrically bonded by piercing clips, become the EGC network.
The old way of grounding
Traditionally, lay-in lugs attached to module frames held a continuous copper wire acting as EGC. This method was parts- and labor-intensive.
Top-down bonding
Bonding washers, like this Wiley (Burndy) WEEB, cut into metal module frames and rack rails to make electrical contact. A variety of styles fit specific rack designs.
The IronRidge module clamp has cutting teeth that make electrical connections (shown in green) at both the module frame and rail.
DP&W offers midclamps with WEEB piercing clips to create the grounding bond to module frame and rail.
The Schletter midclamp has points under the lip to pierce the module frames.
Magerack’s midclamp also has module-frame-piercing teeth.
The IronRidge hardware shows piercing teeth (on the top clamp) and the captive bolt head (at the bottom).
SnapNrack’s top clamp and channel nut both have sharp integrated bonding points.
SnapNrack’s top clamp and channel nut both have sharp integrated bonding points.
Solar SpeedRack’s mounting rails have pre-installed grounding springs that bite into module frames and rails when the module is placed into the rail rack.
Unirac’s bonding midclamp assembly pierces the anodized finish on the module frames to electrically bond modules together.
IronRidge’s braided ground strap, which electrically bonds adjacent lengths of rail.
SnapNrack’s bonding rail couplers join the rails mechanically and electrically.
Spider-Rax’s Red Widow system is a railless mounting solution for composite roofs.
Spice Solar offers IG via its “built-in racking system” for Spice Solar-certified modules.
Quick Mount PV’s railfree rack system employs IG via its panel clamp (see opening page image). This system also offers an array skirt for a finished look.
S-5! midclamps secure and electrically bond the PV module frames for a railless solution on standing-seam metal roofs.
Grounding with piercing clips
The old way of grounding
Top-down bonding

Innovations in PV module rack systems offer more streamlined, straightforward installation, reducing materials and labor.

It seems that each year the photovoltaic (PV) industry makes strides to become more cost-competitive with conventional power sources. From simpler module wiring to combining functions within inverters, equipment manufacturers have found ways to reduce material use (and thus cost). With multiple functions in one piece of equipment, an added benefit is streamlined installation. Module rack systems have likewise evolved, with the result of decreasing installation time. One of the most notable recent innovations in racking is “integrated grounding (IG),” now offered by several rack manufacturers.

To understand what integrated grounding is—and why it is getting much attention in the industry­—you need to understand how time-consuming and detailed the grounding process once was. In the past, an equipment-grounding conductor (EGC) was secured to each module by a lay-in lug. This was attached to the module grounding point with a stainless steel thread-forming screw—after the surface was properly prepared by sanding off the module frame anodization at the point of lug contact. The grounding wire continued in this way from module to module, then to another lay-in lug bonded to the rack, then to any other metallic electrical box, and so on—to connect to the rest of the equipment grounding system (see “Code Corner” in HP102).

Top-Down Shows Up

Soon, “top-down” module mounting—with two rails under each row of modules and the modules secured to the rails by clips accessible from above the modules—became commonplace. End-clips are used to secure modules at the end of each row, and mid-clips are used between adjacent modules. The clips are bolted to the rail; their edges overlap the module frames to secure the module against the rails. Bonding washers placed between the module frame and the rail replaced the lay-in lug and wire. When the clips are tightened, the teeth of the washer pierce both the module frame and the rail to electrically connect the rack and modules.

This method sped up the equipment-grounding process since no surface preparation is required. It also reduced expense—the bonding washers are less expensive than lay-in lugs and the EGC that had to span all the module frames (see “Code Corner” in HP152.)

On to Integration—With or Without Rails

The logical next step in top-down mounting and module grounding is bonding clips that, when bolted down, simultaneously secure the module to the rail, and electrically bond adjacent modules and the underlying rail. It eliminates the need for separate bonding hardware (bonding washers or lay-in lugs). While bonding clips vary in shape and dimensions, all have a method—usually sharp, serrated surfaces—to pierce the frames’ and rails’ anodized coating when the clip is secured.

Integrated grounding is still an innovation, so at this time, each manufacturer typically offers only one rack system with this feature—note the specific rack model(s) in the “Integrated Grounding” table (and don’t assume that all of the other products the manufacturer makes have IG capability).

Comments (3)

Milton P Nogueira's picture

There is one product and manufacturer missing from the article:
RT-[E] Mount and RT-[E] Mount AIR from Roof Tech Inc.
with the following certifications:
ETL to UL 2703 (Bonding/grounding Integrated)
UL 1703 (FIRE)
ICC ESR 3575 (Integrated Flexible Flashing)
Compliant to IBC and IRC 2006, 2009 and 2012
ASTM 2140
PE Reports based on ASCE 7-05 and ASCE 7-10

check our ads at Home Power

Justine Sanchez's picture
Hi Milton, Thanks so much for posting this comment! So when researching information for this article and looking at the installation instructions for this product it appeared that the bonding plate while included in the parts that come with the mounting hardware, still must be placed by the installer, similar to a installation using WEEBs and thus didn't include as we primarily focused on clamps that had integrated teeth into the module-to-module clamping device itself. Please let me know if I mis-understood the manual for this product, and feel free to let us know more about this racking product and it's features. From what I can see it looks to be a rail-free mounting solution, which has the benefits of less materials (including less embodied energy, lower shipping costs & easier to transport to the site). Best, Justine Sanchez Home Power Magazine
Milton P Nogueira's picture

Thank you for your note. The WEEB product is actually part of your article.
I'll be happy to give you a presentation about our product.

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