Hi All, Caution: this is a longish tale about a problem with Outback's FNDC monitor, as well as a request for any other related stories. Sorry for the long post - sharing this here is somewhat therapeutic for me, so if you want to cut to the chase, it is toward the bottom:
About a year ago I installed my second or third FNDC meter into a single off grid VFX3524 OB power panel. I had originally built this panel with an FM80 for the eventual addition of a small array. I removed the FM80 after about 2 months of problem free operation because the client changed their mind about the solar and wanted to stick with just the generator charging the 12 Surrette KS33 batteries (long boring story). The day after removing the FM80 I received a call from he client saying the mate was turning off and on randomly. When I arrived, the Mate, the Hub, and the FNDC were randomly powering off, then back on after maybe 5 seconds, sometimes once, sometimes many times in a row. I checked everything obvious (wiring, cabling, voltages, etc.) and then replaced various, then all comm cables. This was to be the first of many (I mean many) service calls over the next *10 months* trying to solve the problem. Because the symptom was erratic, it appeared at various times that something I changed made the difference. After an hour or 2 of testing with no repeat of the symptom, I conjured up some rational to explain why my particular "fix" du jour worked, congratulated myself that I had solved the problem, and went home (which fortunately is only 50 minutes away). An hour, day, week or two later, I would get another call informing me that my "fix" was insufficient. Each time, I would return with more equipment in hand, over time replacing multiple times the Mate, the Hub, and the FNDC, then all 3 internal VFX boards, checked grounding and wiring for shorts, for surges... I can't remember what. And again each time, I would get the system to settle down, would feel satisfied enough to convince myself to go home, and the cycle would repeat. I had of course included OB support on this journey from the start (which was a bit of a challenge since originally there was no land line, and cell service was a couple miles away - after about 4 months the clients did manage to get the phone company to come through with their land line). OB sent along various replacement parts as we thought new thoughts to experiment with. I think I talked with just about everyone at OB about this issue, and while everyone was fascinated, helpful, and sympathetic, in the end they were not successful at pinpointing the cause. Of everything tried, it turned out that the only reliable action I could take to make the symptom stop would be to unplugged the FNDC comm cable from the hub, although by the time I stumbled across that repeatable experiment, I was so befuddled that it took months for me to realize the consistency and primacy of that behavior. In the end, this was the clue that I used to finally solve the problem (I hope), about a week ago. So last week, after Matt James sent a complete inverter replacement unit under the belief by the engineers that somehow the 22 volt communication power was weak and cutting out upon surges, I replaced the inverter. (Power surges, either charging or loads, seemed associated with the symptom, though not consistently - as well as hitting keys on the Mate.) All seemed well, and I went home, only to get the dreaded call, this time before I even made it home. So I returned the next day with another hub, then replaced the FNDC (again) because it was reporting 2.7 vDC though the inverter was reporting proper voltage, and still got the flashing! I finally surmised (I believe correctly this time) that the flashing happened when there was a large current flow in or out of the batteries. If the batteries were getting charged, the symptom would only appear during the early parts of the charge cycle, unless there was an unusually large load surge as well. And if the system was "on edge" do to medium size current flows in or out of the batteries, any hitting of Mate buttons seemed to be enough to start the cycling as well. THE CHASE: In a flash of inspiration/desperation, I removed the FNDC's voltage sensing cables (the twisted pair supplied with the FNDC by OB) from the conduit which contains the battery cables and ran them to the DC plus and minus busses in the FW500 instead. I had run the wires directly to the battery terminals on the advise of someone(?) thinking this would provide the most accurate operation. The symptom stopped and has not returned to date. Outback has now determined that somehow this induced current from the battery cables into the voltage sensing wires for the FNDC can cause the communication system to get overwhelmed, but they are not quite sure how. None-the-less, as of this week, they are recommending to run the FNDC voltage sensing wires (plus and minus) *not* along side the inverter cables. Hopefully, this is the end of this story... Has anyone experienced any similar symptoms? This seems a first for OB, but I thought I'd ask here. Howie -- Howie Michaelson NABCEP Certified Solar PV Installer™ Sun Catcher, LLC Renewable Energy Systems Sales and Service VT Solar & Wind Incentive Program Partner http://www.SunCatcherVT.com (cell) 802-272-0004 (home) 802-439-6096 _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
