Bob-O:
When you say verboten, what does that mean? Not kosher? Frowned upon? Disallowed by law??? I am quite curious about this subject. Here is what I have learned so far: This is a unique case where we are replacing 3 dead SMA U series inverters with 2 US series inverters. The U series seem to all be dying at about 12 to 14 years of age. We have about a dozen of these to swap on our calendar and expect more. It may be that to do this right requires that we pull new wire from the arrays. This makes the job a lot more expensive. We have never used a wire nut on a PV lead until this project. It's not that we disapprove of wire nuts in general, it is because we know that if we were to use them regularly we would eventually have failures and call backs. We allow only one splice in a PV lead: between the cable provided by the manufacturer of the module and a bulkhead mounted MC4 connector direct to THWN in conduit (http://millersolar.com/MillerSolar/practices/PV_wiring/PV_Cable_wiring/_PV_ Cable_Wiring.html). We checked the manufacturer's listing and the wire nuts are rated for 600 volts. We do use wire nuts on AC circuits, such as switch and receptacle circuits in a power room. A tech at SMA told me that wire nuts "arc internally to the spring" causing the AFCI faults. I am not aware of any process of "internal arcing." To me, arcing means, as per the dictionary definition: "a luminous bridge formed in a gap between two electrodes." The same tech told me to solder the leads and apply shrink tubing. I don't believe this is an approved method. By the way, we have spliced leads on both US series inverters and only one is exhibiting AFCI disturbances. I do favor mounted terminal blocks, either screw or tubular type. I need to check if the Amp model we stock are 600 volt rated. I was told by another representative from SMA that on a ground-mount system it is legal to disable the AFCI protection. I will be troubleshooting this job tomorrow and I will let you all know what I learn. William Miller Lic 773985 millersolar.com 805-438-5600 -----Original Message----- From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Bob-O Schultze Sent: Tuesday, June 24, 2014 11:16 AM To: RE-wrenches Subject: Re: [RE-wrenches] AFCI disturbances. Wire nuts on the DC side have been verboten in Oregon for over a decade. IMO, copper split bolts wrapped with insulating then regular tape are the way to go. Back in the days of 12V system and no series fusing, we used to use them all the time to combine PVs. I've gone into some of those systems a decade later and found the bolts to be discolored by the tape on the outside but the wires bright and tight under the bolts. On Jun 24, 2014, at 9:35 AM, William Miller wrote: Steve: The PV is 200 feet away on the other side of a building. We have THWN in PVC conduit. This job was installed over 10 years ago. We don't want to re-pull all of the leads for 6 strings in PV wire. We Void splices like the plague but the PV leads terminated in a HU361 switch and we needed to splice on some short leads to make this work. Are you telling me we can no longer use 600 volt rated building wire and/or standard 600 volt rated wire nuts on PV circuits with your products? If so, this is a BIG deal for installers. Thanks, William Miller Solar > On Jun 24, 2014, at 8:52 AM, Steve Jefferson <steve.jeffer...@sma-america.com> wrote: > > Morning William, > > You can contact me offline, or better yet, call our Service Line. I checked and see no calls in about AFCI issues. > > Also, we don't recommend wire nuts on DC conductors (or AC) due to the probability of unreliable and highly resistive connection. > > Thanks > > SMA America, LLC > Steve Jefferson > Service Line Supervisor > 3925 Atherton Ave > Rocklin, CA 95765 - 3714 > U.S.A. > Tel: +1 916 625 3185 (direct) > Fax: +1 916 625 0871 > Mobile: +1 916 622 4253 > Email: steve.jeffer...@sma-america.com www.SMA-America.com > > > > This email and any attachments thereto may contain SMA America, LLC confidential, privileged and private material for the sole use of the intended recipient. Any review, copying, or distribution of this email (or any attachments thereto) by others is strictly prohibited. If you are not the intended recipient, please contact the sender immediately and permanently delete the original and any copies of this email and any attachments thereto. Thank you. > > > > -----Original Message----- > From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] > On Behalf Of William Miller > Sent: Monday, June 23, 2014 3:40 PM > To: RE-wrenches > Subject: [RE-wrenches] AFCI disturbances. > > Friends: > > We are starting to replace dying SB2500s with new units. The AFCI is giving us fits with disturbances. We are told we cannot even use wire nuts. > > Has anyone else dealt with this? What have you learned? > > Thanks in advance. > > William > > Miller Solar
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