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Thread: Purpose of the weeb

  1. #1
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    Purpose of the weeb

    In an Enpahse micro-inverter system, does the listed weeb used on the micro-inverter take the place of the GEC? Or is a seperate GEC required as well?

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    Separate GEC needed.

    However, the newest 250 Enphase may not need a GEC.

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    I agree with Zee. I always thought it was bit odd that Enphase showed the weeb as an option at all. They were clearly counting on the idea that some AHJs wouldn't believe there was a need for a GEC.

    It remains to be seen how AHJs will react to Enphase's assertion that the new M250 doesn't require a GEC.

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    Quote Originally Posted by jaggedben View Post
    I agree with Zee. I always thought it was bit odd that Enphase showed the weeb as an option at all. They were clearly counting on the idea that some AHJs wouldn't believe there was a need for a GEC.

    It remains to be seen how AHJs will react to Enphase's assertion that the new M250 doesn't require a GEC.
    OK, so here's the $64 question, what's the down side of having installed systems without GEC's?

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    Quote Originally Posted by jaggedben View Post
    I agree with Zee. I always thought it was bit odd that Enphase showed the weeb as an option at all. They were clearly counting on the idea that some AHJs wouldn't believe there was a need for a GEC.
    Jben,
    Very apropo that you bring up what the purpose of the WEEB is for an Enphase micro-inverter. We just figured it out, it was a mystery......
    It is to bond the racking to the inverter, not vice versa. That is to say, in order to continue the EGC and bonding of the rack - thru the rail with the WEEB, into the inverter body, which in turn is bonded with the grounding wire provided inside the AC cabling.
    In other words: you can put WEEB washers on the module clamps, a WEEB on the micro, and you are done with bonding.
    Still need the GEC. That is not bonding.
    But no WEEB splices from rail-end to rail-end horizontally; and no EGC bare copper nor WEEB-Lugs running vertically from one row to another row of rails!
    Am i off my rocker?

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    Re. the Enphase M250 and whether GEC is needed

    http://enphase.com/global/files/M250-with-IG.pdf


    pretty exciting.

  7. #7
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    Quote Originally Posted by Zee View Post
    Jben,
    Very apropo that you bring up what the purpose of the WEEB is for an Enphase micro-inverter. We just figured it out, it was a mystery......
    It is to bond the racking to the inverter, not vice versa. That is to say, in order to continue the EGC and bonding of the rack - thru the rail with the WEEB, into the inverter body, which in turn is bonded with the grounding wire provided inside the AC cabling.
    In other words: you can put WEEB washers on the module clamps, a WEEB on the micro, and you are done with bonding.
    Still need the GEC. That is not bonding.
    But no WEEB splices from rail-end to rail-end horizontally; and no EGC bare copper nor WEEB-Lugs running vertically from one row to another row of rails!
    Am i off my rocker?
    OK, so please help me understand this. What gets connected to the GEC? Just the microinverters? Does the GEC need to be continuous back to the panel, or can it be combined with the EGC in the j-box on the roof (assuming it is sized large enough). Can you advise how the GEC is typically installed. Much thanks for your advice.

  8. #8
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    Typically:
    GEC from inv. to inv.
    Same GEC continues thru rooftop j-box down to MSP.
    This single GEC IS UNSPLICED UNCUT CONTINUOUS THRU-OUT.

    I use THWN-2 stranded #8 and strip insulation at each enphase lug. The stranded and insulated is easy to pull in conduit.

    EGC (bare copper #10 solid) and WEEBS must bond every rail and every module.
    This rooftop EGC can be spliced TO GEC in rooftop j-box. Split-bolt. Point is that EGC is cut, not GEC.
    Hence you have a single #8 GEC/EGC running in conduit down off roof.

    Use racking listed for WEEBS and enphase.
    Just use a WEEb on each enphase to bond the rail to the module.
    WEEb on every module clamp (don't be cheap, put it on every clamp, i say) to bond module to rail.
    Use a WEEB-Lug and #10 wire on any rail that is not bonded by above.

    Stop and reconsider: has every rail, module and inverter been bonded?

  9. #9
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    Quote Originally Posted by Zee View Post
    Typically:
    GEC from inv. to inv.
    Same GEC continues thru rooftop j-box down to MSP.
    This single GEC IS UNSPLICED UNCUT CONTINUOUS THRU-OUT.

    I use THWN-2 stranded #8 and strip insulation at each enphase lug. The stranded and insulated is easy to pull in conduit.

    EGC (bare copper #10 solid) and WEEBS must bond every rail and every module.
    This rooftop EGC can be spliced TO GEC in rooftop j-box. Split-bolt. Point is that EGC is cut, not GEC.
    Hence you have a single #8 GEC/EGC running in conduit down off roof.

    Use racking listed for WEEBS and enphase.
    Just use a WEEb on each enphase to bond the rail to the module.
    WEEb on every module clamp (don't be cheap, put it on every clamp, i say) to bond module to rail.
    Use a WEEB-Lug and #10 wire on any rail that is not bonded by above.

    Stop and reconsider: has every rail, module and inverter been bonded?
    Thanks so much for the info. I'm doing a little less head scratching now. Just a couple of clarification questions. What does MSP refer to? Are we talking about the main bonding point in the panel? Also, does 690.47(C)(3) allow a single conductor to serve as both EGC and GEC, provided it is sized per 250.166?

  10. #10
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    Quote Originally Posted by csoc64 View Post
    Thanks so much for the info. I'm doing a little less head scratching now. Just a couple of clarification questions. What does MSP refer to? Are we talking about the main bonding point in the panel? Also, does 690.47(C)(3) allow a single conductor to serve as both EGC and GEC, provided it is sized per 250.166?
    MSP is Main Service Panel.

    Regarding 690.47(C)(3), you have it basically correct. It allows a single conductor to serve as both EGC and GEC, provided it is sized for the larger of either requirement. On residential systems this almost always means going with the minimum #8 for a GEC according to 250.166, since the 250.122 requirement for an EGC is smaller up to 60A.

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