Hi Nick, Waddya mean "another supply side tap nightmare"? This isn't the first? RE: "Void the listing..." Let's be honest. I don't know about you or anyone else on this list, but I'm pretty sure that every single supply side connection I've seen in wall-mounted meter/main combination service panels has voided the listing on the thing. These were factory assembled and listed as such. Just because, "it's been done before", does not change the fact that it's not what the panel manufacturer had in mind when the thing originally left the factory. This applies to equipment with conductors as well as busbars. If they had intended connections such as this, they would have provided the means to do it and listed (no pun intended) the approved devices on the label inside the cover. The label that is no longer legible.... If an inspector plays the "all equipment must be listed for the use" card, you have a couple options. Smaller PV system on a load side connection comes to mind. Larger service panel comes to mind. Different service configuration (i.e. separate meter socket), comes to mind. Paying for a NRTL to list the final product comes to mind, along with a few cuss words. Pissing up a rope trying to get the guy to back down from his 100% defensible position is not jumping out there as a viable option to me. I'm not exactly sure what you hoped to gain by swapping from TW to THHN from a code perspective.... I fully understand your service entrance feeder table concept, but what do you gain, really? Other than the fact that you will be violating the listing by tapping in that section anyway, you can theoretically put up to 110A of PV on that conductor and stay with the #1AWG TW (Table 310.16) under all the tap rules, etc. The utility is upstream of your connection and the downstream (house) is protected by the 100A main breaker. Unless it's an FPE, or Bulldog, or Zinsco... In those cases, Buddha alone knows how many amps shall pass and sparks shall fly before the breaker trips... Are you putting in more than 100A of PV on a utility service that is sized for 100A? If that's the deal, then a bigger service is necessary. (Side Note: IMHO, PV output capacity greater than the customer's service needs shouldn't qualify for Net Metering in any way shape or form.) Just because the whole listing thing around supply side connections is what it is, doesn't mean that one could not SAFELY accomplish a supply side tap in some of these boxes. (Note: Double negative = positive, in case you missed it.) Some, but certainly not all. The problem is, "Safety" is subjective. What one person calls safe, I might not, and vice versa. This is where standards come into place. Standards, such as UL XXXX, are developed to define the conditions that constitute safety in various products depending on their use. NRTLs judge whether a product meets these conditions or not. If the product meets the conditions, the NRTL lists the product to such and such a standard. The NEC defers to listing as the be-all-end-all. As do building officials in many cases. Some use this as a club to hide their own incompetence, no question. That being said, we I wouldn't normally bring all this up in this venue, but from what I am seeing, the cat is out of the bag already... The horse has left the barn... I suspect that, in most cases, supply side connections will largely be a theoretical concept only in the very near future. We must push equipment manufacturers to develop products which facilitate safe, code-compliant interconnection at existing services. I would contact a company like Marwell http://www.marwellcorp.com/ and describe your supply side connection woes.... For small to modest size systems, I think going right in behind the meter is best done outside the box.... Look for an E/Z 1000-0 meter extender in the configuration you like from this page http://www.marwellcorp.com/online-catalog/5-1000. You can order it with KO up to 1". It's not standard a standard option for this extender, but tell them you want NC-400-L clips on the load jaws. You will need to get them to buy off on it, but most utilities will accept it, though they may want to put a lock on it. The trick is getting your neutral conductor routed through it. It's a place to start... Matt Lafferty
_____ From: [email protected] [mailto:[email protected]] On Behalf Of Nick Vida Sent: Friday, November 20, 2009 4:37 PM To: wrenches Subject: [RE-wrenches] "its a UL listed assembly" wow wrenches, fun solar day for me. Another supply side tap nightmare. Have any of you ran into a situation where the AHJ will not let you upgrade the feeders from the meter to the main breaker because it "voids the UL listing"? In this case I had 1 AWG feeding a 100 amp main, but it was type TW which is not on the feeder exception 310.16. In running into the typical daftness on 690.64 I asked if I could replace the 1 AWG TW with Type THHN so the feeder chart would apply and there would be 150 ampacity wires feeding the 100 amp main. No luck, all frustration. Any wrenches have any thoughts on this? Nick Vida
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