William,
I was also surprised to see SMA go down this road (ala Fronius IG). I can’t speak to why they did this. I’m installing my first 40 series right now. I have never supported covering the array as a viable method of removing voltage. It is far safer to unplug the strings on the roof if you want to remove voltage. Not sure why they did not suggest unplugging instead of tarping. Either way, many jurisdictions will require an external dc disconnect with this new configuration—what a waste. If SMA were smart, they would put connectors in their dc connection box to be compliant with the 2017 NEC which would solve their problem. It means a design change. They must be expecting this product to be connected to a rapid shutdown switch box—that’s the only thing that makes sense. Bill. From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller Sent: Wednesday, December 14, 2016 10:45 AM To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] SMA 40 series DC disconnect Bill: That is exactly my point. Carports and ground-mounts do not need RS, but any system requires safe means to disconnect DC. So how do you accomplish this with the 40 series? Sure, using the DC connector is one way to disconnect the DC input to the 40 series electronics. However, the service manual cautions against this. Below is the verbatim text from the manual. >From SMA Document SB30-77-1SP-US-40-AT-PU-SG-xx-11 Service Manual: • If an external DC disconnecting switch is available, open the external DC disconnecting switch. • If there is no external DC disconnecting switch, cover the PV modules with opaque material (e.g. foil). • Ensure that there is no voltage on the DC conductors of the PV array. • Wait five minutes before working on the inverter. • Leave the DC-in connecting terminal plate plugged into the Connection Unit and only touch it on the black enclosure. I was told that the term ‘foil’ is a poor translation from German, and likely means a tarp. In any event, this verbiage is quite unfortunate as it precludes using the connector as a disconnect. I wonder if there is some criteria on what kind of connectors can be used as a disconnecting means and which cannot. I am sure it has something to do with ‘touch-safe’ requirements. The DC connector in the 40 series may not meet this criteria. The external leads could possibly come free of the connector body as they are just insert-connected. I would be very reticent to send out a technician to work on one of these without some serious consideration of the implications. SMA seems like they are interested in this conundrum and I am withholding judgement pending receiving a response from them. I just thought it very curious that they moved the location of the disconnect in the DC power flow scheme. Seems to me like a fundamental change that flew under the radar. See below for a rendering of the change in DC power flow: Formerly: PV-------->Integrated Disconnect------>chassis separation 40 Series: PV ------>chassis separation-------->Integrated Disconnect William PS: I remember wasting an entire afternoon in a conference room in San Diego arguing with Fronius about the same concept. They too insisted that to service the IG series inverter one had to just tarp the modules. Let us please put that myth to rest once and for all: Tarping modules is not viable. Wm Lic 773985 millersolar.com <http://www.millersolar.com/> 805-438-5600 From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org <mailto:re-wrenches-boun...@lists.re-wrenches.org> ] On Behalf Of billbroo...@sbcglobal.net <mailto:billbroo...@sbcglobal.net> Sent: Wednesday, December 14, 2016 7:40 AM To: 'RE-wrenches' <re-wrenches@lists.re-wrenches.org <mailto:re-wrenches@lists.re-wrenches.org> > Subject: Re: [RE-wrenches] SMA $0 series DC disconnect William, I’m not sure you meant to imply this, but carports and ground mounts do not need any RS equipment unless you were to bring the dc conductors into a building, which would not be smart. The 2017 NEC allows connectors to be used as isolation devices for equipment as long as the circuit current is below 30 amps, which it always is on individual strings. I realize California will not be on the 2017 for 3 years, but it will make installations cheaper, not more expensive. Electronics are destined to become a bigger part of PV arrays in the future—and not just because of rapid shutdown requirements. It just makes sense in building applications for many reasons. The keys will be cost and reliability. Bill. From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller Sent: Tuesday, December 13, 2016 5:39 PM To: RE-wrenches <re-wrenches@lists.re-wrenches.org <mailto:re-wrenches@lists.re-wrenches.org> > Subject: [RE-wrenches] SMA $0 series DC disconnect Friends: I am taking a poll to see if any of you have noticed the change in the SMA 40 series DC disconnect as compared to earlier series inverters and how it may be affecting your installations. The DC disconnect is no longer in the lower, connection box area, but in the electronics area. This means it will not de-energize the DC connections. Certain jurisdictions will not allow us to install this unit without an external disconnect. The service manual addresses the subject. The Remote Shutdown Box unit may provide a means to de-energize PV sources, but in a webinar today SMA claims it does not meet code, possibly in regards to lock-out capability. It actually looked viable to me, but that is not based on any research. Soon all or most building mounted PV arrays will require Rapid Shutdown. This will add hundreds of dollars to the cost of an install, but safety is safety. What may sting is adding $400-500 of RS equipment to a carport or ground mount where it may not otherwise be required. SMA has concurred that the issue bears further discussion and I should hear back from them soon. In the meantime, I thought it might be useful to all parties to see how much impact this change in design is having to other installers. Thanks in advance for any input. I will report back on what I learn. William Miller Lic 773985 millersolar.com <http://www.millersolar.com/> 805-438-5600
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