Hi Brian,
Very good points. In function, the frames of the modules and the
aluminum racking are grounding bus bars that are connected together
with bolts and rivets (Weebs). This method is allowed by 250-64 C
2. All that is required is for inspectors / code writers to
acknowledge that the frames and rails fit this definition. It may
require additional wording or an exception.
This is not an issue of safety, function or science, but one of semantics.
Drake
At 05:31 PM 1/17/2013, you wrote:
Hi John,
You have brought up several points.
1. practical answer
The NEC says that a GEC can be solid aluminum. PV mounting rails are
typically aluminum. It is easy to calculate the ampacity of a solid
aluminum piece from its cross-section.
Even the lightest rails on the market have an ampacity that is an
order of magnitude greater than the copper wires required by code for GECs.
The 2011 NEC, section 250.64(C)(3) says that "Bolted, riveted or
welded connections of structural metal frames ... of structures" are
permitted splices for the GEC.
The WEEB is a tested and characterized device and therefore
preferable to one that, while allowed by code, has not been
characterized at all.
2. listing
There is no standard to list equipment for use as a GEC or an EGC.
The lack of a standard does not mean equipment is not suitable, it
just means we need to use good engineering judgement until the codes catch up.
Does new equipment meet the intent of the existing code? Are there
any valid engineering reasons not to use new equipment? I think
those are the questions we should focus on.
Note that the WEEB was introduced almost 7 years ago and these code
issues still have not been resolved to everyone's satisfaction.
3. connecting to a copper wire
Jason Szumlanski discussed this already, but I will reiterate. When
you connect a GEC to a string inverter it is done in a reversible
manner, typical with a screw connection. When you connect to a PV
system, consisting of multiple distributed inverters, you can do so
with a reversible connection, typically a listed lug, anywhere on
the PV system.
Best Regards,
Brian Wiley
On 1/17/2013 10:58 AM, John Berdner wrote:
Jay:
You raise an interesting question.
I believe the structure would have to be evaluated and Listed for
equipment grounding (UL is working on a new Standard for this now)
AND for use as a GEC (which I don't think is possible).
Even if the WEEB was approved for use as a GEC (I still do not feel
this is the case) the rail then needs to be contiguous or
irreversibly spliced to the copper GEC.
I am not aware of any Listed hardware that facilitates this.
Anyone know of any ?
We also have a dissimilar metals problem irreversibly crimping or
exothermic welding (the Code requirement) copper to aluminum.
Best Regards,
John Berdner
General Manager, North America
Solaredge Technologies, Inc.
3347 Gateway Boulevard, Fremont CA 94538 USA (*Please note of our
new address.)
T: 510.498.3201 ext 747
M: 530.277.4894
From:
<mailto:re-wrenches-boun...@lists.re-wrenches.org>re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of jay peltz
Sent: Wednesday, January 16, 2013 8:52 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] GEC for Micro-Inverters and ACPV Modules
Dear John and Brian
Thanks for a great discussion.
My question is:
If you used a WEEB to connect the inverter to the rail, is the rack
rail listed as a GEC?
Or does it have to be listed as a GEC?
Thanks
Jay
Peltz power
Sent from my iPad
On Jan 16, 2013, at 12:09 PM, Brian Wiley
<<mailto:btwinfin...@gmail.com>btwinfin...@gmail.com> wrote:
Hi John,
I don't feel that you are argumentative. I am glad for this forum
and people to put forth honest opinions.
I think you just may not be aware of how the WEEB actually works.
It is a type of rivet, not just a pronged thing that makes
connection as part of a bolted connection.
It does use a bolt to engage the part, but the teeth on the WEEB
are specially shaped. When the bolt is torqued, the teeth deform,
similarly to a rivet.
The metal that it is connecting to mushrooms up around the tooth
and the tooth pinches in around the metal.
This deforming action is what forms an exceptional electrical
connection and also forms an air-tight seal between the part and
embedded metal to resist corrosion.
If you remove the bolt, the WEEB will still be connected to the
metal. You must forcibly remove the WEEB from the metal.
Hope that clears things up for you.
Best Regards,
Brian Wiley
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