csoc64...what brand/model solar modules are on the job?
The WEEB clip positively bonds the Enphase inverter metallic case to a metallic rail as part of the grounding system by penetrating any oxides or coatings on the rail or inverter case. It is quick and easy.
Reference Enphase M215 and Engage cable: The M215 inverter has 4 wires - 2 line (red, black), 1 green equipment grounding conductor (EGC), one white grounded conductor (N). The green wire (EGC) IS NOT bonded to the metallic inverter case. The inverter also has a built-in lug.
The Enphase Engage cable also has 4 wires of the same colors. Using standard wiring methods will bring the circuit back to the main panelboard . Of course, the green wire is not bonded to the white (N) until at the main service panel where they are bonded together.
Since all exposed metallic parts of the PV system must be bonded together in an equi-potential plane as part of the grounding system,
the WEEB clip easily bonds the inverter metal case to the metallic rail in a similar manner as a copper water pipe.
With the inverter case bonded to the metallic rail, the metallic rail(s) are then bonded together using approved lugs or clips to the grounding electrode conductor (GEC) which is then bonded to the grounding electrode near the service panel.
In lieu of a WEEB clip. a properly sized copper conductor can be bonded to each inverter case (as the GEC) using the provided lug. Each rail supporting the PV panels is also bonded to the grounding system by an approved lug holding the GEC.
Using WEEB clips is much faster and cheaper than running long lengths of copper wire to all the components.
As an aside, WEEB clips can also be used to bond the metallic frames of the PV panels to the grounding system instead of using copper conductor and lugs.
There's a pretty clear argument to be made that the GEC must be continuous or irreversibly spliced from the inverter to the grounding electrode, per the code. (That is based on the article 100 definition of a GEC, 690.47, and 250.64.) Perhaps a connection to a grounding busbar is sufficient per 690.47(C)(3), but a WEEB is definitely not an irreversible splice.In lieu of a WEEB clip. a properly sized copper conductor can be bonded to each inverter case (as the GEC) using the provided lug.
As a matter of opinion, I think that it's a bit over the top that we have (in effect) more stringent grounding requirements for microinverter systems operating at less than 50VDC than we do for string inverter systems at up to 600VDC. But as far as the current code, it doesn't allow a WEEB to be a GEC. With that said, I understand that the 2014 will introduce some changes in this regard.
The WEEB is a UL 467 grounding and bonding device listed by ETL...
No matter what the WEEB is actually for, on our solar install crew it is required to sing this song when installing them:
"A WEEB-a-way A WEEB-a-way A WEEB-a-way A WEEB-a-way
On the roof, the mighty roof, the WEEB gets torqued tonight
On the roof, the mighty roof, the WEEB gets torqued tonight"
Now you'll have that stupid song in your head all day. Muwahahahaaa!
Lawrence Lile, P.E.