Karl,
What you are referring to is a "reverse power relay." These are common devices used for customer-generators. Basler is one company that makes them. Just google the topic and you will find several companies. The utility may have a preferred product so go with them if they have one. There are a few PV installations with these devices. It simply sends a signal to trip a relay at the inverter if reverse power is ever measured at the service entrance. It sounds like it is unlikely the device will get much use except on very special occasions when there servers are offline. Bill. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Karl Jaeger Sent: Tuesday, February 15, 2011 3:41 PM To: RE-wrenches Subject: Re: [RE-wrenches] "Keep that there PV off my grid!" Dana, This is an instant excess situation, not one electron. I am not sure if this violates federal regulations, but you make a valid point. I will have to look into it. Honestly, there is a very small probability that any PV will ever make it to the grid. The service is 1000 Amps and the building has multiple servers running continuously, all day every day. I am hoping to forego the dumpload option and the added costs. Word is, they will begin discussions in the coming months addressing this issue. In the case that they decide to allow it, it would be an easy fix to remove the contactor and splice the conductors. I have heard rumors that a contactor like I described does in fact exist. But that was some years ago and I cannot remember the details. Thanks, Karl Jaeger Operations Manager LightWave Solar Electric www.lightwavesolar.com From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Dana Sent: Tuesday, February 15, 2011 4:31 PM To: 'RE-wrenches' Subject: Re: [RE-wrenches] "Keep that there PV off my grid!" Karl - Is this instant excess or excess during a specific billing period? Does this violate Federal regulations? Could you divert or bank the excess in process heat, water pumping, or some other function? Dana Orzel Great Solar Works, Inc E - <mailto:d...@solarwork.com> d...@solarwork.com V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 web - <http://www.solarwork.com> www.solarwork.com "Responsible Technologies for Responsible People since 1988" Do not ever believe anything, but seriously trust through action. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Karl Jaeger Sent: Tuesday, February 15, 2011 3:21 PM To: re-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] "Keep that there PV off my grid!" Greetings Esteemed Wrenches, My company was recently tasked to engineer a PV project in Alabama. We sat down for a meeting with all of the local big-shots. They proceeded to let us know that we are not allowed to feed any excess PV power onto their grid, production cannot exceed demand. I am hoping that y'all might be able to steer me towards a contactor assembly or device that would detect reverse current flow, trigger the contactor, then open up the inverter AC output circuit. The service is 3-phase, 208 volt. The maximum current we intend to introduce is 70 amps, continuous. Appreciate your advice, Karl Jaeger Operations Manager LightWave Solar Electric www.lightwavesolar.com
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