<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman,new york,times,serif;font-size:12pt"><div>Thanks for a great response Matt, and an interesting lead to a product solution...<br><br>Let me preface this with saying I am installing another company's design, so all you are saying about proper<br> gear at the service is totally heard, and this tap would not be something I would design...<br><br>The situation is a Wadsworth tandem 100amp main. Really rare and weird panel from the early 60s. It has<br> 2 service entrance masts, and a 8 jaw meter socket feeding 2 separate fused 100 amp load centers.<br><br>The design was to tap into one of these with 40amp fused disconnect from a sma 7000.<br><br>Unfortunately the wires in the Wadsworth gear is type TW which is not included in the Feeder exception of<br> 310.16. When this was discussed. I threw out there the idea of
changing the wires. These guys wanted to<br> void the listing for piercing taps and any other taps <br><br>The REAL problem is the wording of NEC 690.64(B) because all these guys that are not willing to wrap<br> their head around what the signal path/ back feeding/ over-current/ 230 tapping scenarios are... read 120<br> and wants to apply it to everything in the system. These inspectors were explaining to me that the feeder IS<br> the buss and 120%... and its really hard to explain the intent with the language of the paragraph. It needs to<br> be 2 separately described scenarios in my opinion, to avoid the constant misunderstanding.<br><br>Also, the NEC says in 690.64 and the 230 reference there, that taps are permitted for solar... not much<br> detail, not much help. <br><br>It seems like these inspectors consider the "voiding the UL listing" is a dead wall conversation ender. I'm<br> almost willing to admit you are
right, it is totally valid, which makes the point of .64 come into question.<br><br>I hope you are right about newer gear having listed tapping means and large buses for solar. It seems like<br> that will take a while to filter down because so many people work with electricians different than the solar<br> installers they are working with (and because so many installers focus on solar and don't wire houses). I<br> think the glimmer of hope that a tap will pass on a retrofit is gonna keep them around for some time. And I<br> really think that the code needs to address the options better.<br><br>looks like someone involved here is buying a service upgrade. surprise!<br><br><br><br><br><br></div>
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