After looking everything over from PV solar panels to AC power panels, my inspector applied the coveted green sticker and said, "Nice work." What do you do for a living, he wondered. I replied that I'm an electrical engineer. His reaction was, Oh, now I get it. IMG_2564.jpg
Two strings, each occupying two rows of REC TwinPeak 290W panels. IronRidge mounting with 45 degree elevation.
The series connection of each string starts from the lower right panel and goes to the left where it returns via the upper row of panels. Late afternoon spring and fall shading courtesy of a big beautiful larch I can't quite bear to cut down. Yet. At least it loses its needles in winter.
IMG_2703.jpg
Custom built equipment shed, with PV conductors coming in from the trench at the right and AC conductors going out via the EMT attached to the fence. The smaller EMT is for Ethernet cable and control wires for a solid-state relay.
There are four PV circuits coming through that conduit (1 1/4" IMC transitioning just above grade to EMT), through a 10x9 tray cable, i.e., 10 AWG with 9 conductors. By using IMC conduit, I was able to get away with a shallow trench just 6" deep, thus minimizing root damage to the trees around the path from shed to panels.
IMG_2415.jpg
The wires (600V rating) are all wrapped in two protective jackets (a clear crinkly inner jacket then some heavy black rubbery stuff), and the cable is listed for direct burial. The photo above was taken inside the junction box by the PV array before I got the PV wires attached. You can see how each wire of the tray cable attaches to the bottom of a Euro style feedthrough connector. The PV wires of each string attached to the top: String 1, + to red, - to blue. String 2, + to orange, - to black. I have two more strings planned for an array that will point straight up in front of the tilted array to collect photons from our often grey Washington skies during cloudy weather, and those will go to the other tray cable wires. The spare yellow wire I phase-taped with green stripes (not yet shown) and used as an EGC in addition to the EGC provided by the metal conduit.
With high voltage and modest current and no NEC fusing requirements, this is a highly efficient way of transmitting 6 kW over 150 feet. I'm really happy with how it turned out.
IMG_2706.jpg
Front view of the equipment shed. EMP resistant (about 20 dB of Faraday cage signal attenuation at 2.4 GHz), waterproof, and--best of all--exempting me from all the NEC's new rapid shutdown and arc fault BS. Air intake vent on the left, and outlet vents above the doors. Next to the inlet vent is a 30A generator inlet.
IMG_2704.jpg
IMG_2705.jpg
I got pretty handy with my two conduit benders. (There's a lot more conduit inside the house, with a total of around 120 feet and some 900 degrees of total bend from equipment shed to the AC power panels.)
IMG_2726.jpg
I built the equipment shed to just meet the NEC requirements for working space, which was actually a bit of a challenge. The studs along the back are 2x6, cut down to 2x4 below the oak plywood board. That was so the batteries could go back a bit further and stick out less than 6" in front of the equipment fronts, an NEC requirement. It does make for a comfortable work environment.
There is a Morningstar ground fault protection device for each TS-MPPT-600-48 charge controller. I added a 600V surge protection device inside each GFPD, mounted on the DIN rail it includes for whatever you want to put there. The wiring from the CCs to the Outback rat's nest, aka "load center," is 6 AWG with an 8 AWG EGC. If it were inside conduit, it would have been too small to meet code for the 60A maximum that travels through it, given the summertime temperatures of around 110 degrees F expected inside this shed.
I have no problem leaving 48 V wires exposed inside a locked shed, but did want the 600 V stuff wrapped up inside metal all the way.
IMG_2723.jpg
My custom-built combination combiner and switch box, all nicely NEC-labeled to advise the many different personnel who will be looking inside it. (Um, actually there will be just one, the guy who freaking designed and built the whole thing. But I digress...) The box, DIN rail, and ferrite cores were from Digi-Key, and the disconnect switches from some outfit I found online. Very reasonably priced, and they disconnect both positive and negative as required by NEC (and common sense).
The ferrite cores are part of my indulging an apocalyptic fantasy about surviving an EMP attack. (Don't judge...) Between the 150+ feet of ferrous metal conduit, which represents a waveguide below cutoff at EMP E1 pulse frequencies, the very lossy RF transmission line represented by the tray cable, the 150 Ohms or so of RF impedance from the ferrites, and my surge protection devices, I feel pretty confident that my PV array will not act as an antenna to fry my equipment from outside my big ugly Faraday cage.
IMG_2728.jpg
The MATE3 showing that the thing can produce power, along with an Ethernet switch and home-built Raspberry Pi computer. Those latter items are powered via 12 V stepped down from the big battery with a DC-DC power supply (all parts from DigiKey). Of course there is a properly sized fuse protecting the wiring to the DC-DC supply.
The two charge controllers, the MATE3, and my computer are accessible to me via TCP/IP.
The terminal strip is currently just attached to one control circuit feeding a solid-state relay that feeds my chest freezer. It's a load that can be turned off at night if I wind up off-grid for any length of time--essentially a thermal battery. The relay control comes from the Outback Radian's AUX output in "load shed" mode.
IMG_2719.jpg
The Outback GSLC is a rather cozy little space to do wiring in. But it does provide everything you need, and lots of knockouts wherever you might need them. I wound up having to remove all the stock wiring and starting over, using the wire segments Outback provided where I could. I didn't use their ground-fault breaker assembly at all, but it cost no more to order the fully loaded GSLC than to buy a bare one along with the parts I did need. Note the HUB mounted on the left, and a Midnite AC surge protector on the AC grid input.
Also note the insulating bushings at various important places. The insulation would be a dangerous mess without them. The NEC actually makes a lot of sense sometimes. I couldn't have done all this without my well-thumbed NEC 2017 paperback edition.
(Due to image attachment limits, continued in a comment below, which hopefully will get approved soon.)
Two strings, each occupying two rows of REC TwinPeak 290W panels. IronRidge mounting with 45 degree elevation.
The series connection of each string starts from the lower right panel and goes to the left where it returns via the upper row of panels. Late afternoon spring and fall shading courtesy of a big beautiful larch I can't quite bear to cut down. Yet. At least it loses its needles in winter.
IMG_2703.jpg
Custom built equipment shed, with PV conductors coming in from the trench at the right and AC conductors going out via the EMT attached to the fence. The smaller EMT is for Ethernet cable and control wires for a solid-state relay.
There are four PV circuits coming through that conduit (1 1/4" IMC transitioning just above grade to EMT), through a 10x9 tray cable, i.e., 10 AWG with 9 conductors. By using IMC conduit, I was able to get away with a shallow trench just 6" deep, thus minimizing root damage to the trees around the path from shed to panels.
IMG_2415.jpg
The wires (600V rating) are all wrapped in two protective jackets (a clear crinkly inner jacket then some heavy black rubbery stuff), and the cable is listed for direct burial. The photo above was taken inside the junction box by the PV array before I got the PV wires attached. You can see how each wire of the tray cable attaches to the bottom of a Euro style feedthrough connector. The PV wires of each string attached to the top: String 1, + to red, - to blue. String 2, + to orange, - to black. I have two more strings planned for an array that will point straight up in front of the tilted array to collect photons from our often grey Washington skies during cloudy weather, and those will go to the other tray cable wires. The spare yellow wire I phase-taped with green stripes (not yet shown) and used as an EGC in addition to the EGC provided by the metal conduit.
With high voltage and modest current and no NEC fusing requirements, this is a highly efficient way of transmitting 6 kW over 150 feet. I'm really happy with how it turned out.
IMG_2706.jpg
Front view of the equipment shed. EMP resistant (about 20 dB of Faraday cage signal attenuation at 2.4 GHz), waterproof, and--best of all--exempting me from all the NEC's new rapid shutdown and arc fault BS. Air intake vent on the left, and outlet vents above the doors. Next to the inlet vent is a 30A generator inlet.
IMG_2704.jpg
IMG_2705.jpg
I got pretty handy with my two conduit benders. (There's a lot more conduit inside the house, with a total of around 120 feet and some 900 degrees of total bend from equipment shed to the AC power panels.)
IMG_2726.jpg
I built the equipment shed to just meet the NEC requirements for working space, which was actually a bit of a challenge. The studs along the back are 2x6, cut down to 2x4 below the oak plywood board. That was so the batteries could go back a bit further and stick out less than 6" in front of the equipment fronts, an NEC requirement. It does make for a comfortable work environment.
There is a Morningstar ground fault protection device for each TS-MPPT-600-48 charge controller. I added a 600V surge protection device inside each GFPD, mounted on the DIN rail it includes for whatever you want to put there. The wiring from the CCs to the Outback rat's nest, aka "load center," is 6 AWG with an 8 AWG EGC. If it were inside conduit, it would have been too small to meet code for the 60A maximum that travels through it, given the summertime temperatures of around 110 degrees F expected inside this shed.
I have no problem leaving 48 V wires exposed inside a locked shed, but did want the 600 V stuff wrapped up inside metal all the way.
IMG_2723.jpg
My custom-built combination combiner and switch box, all nicely NEC-labeled to advise the many different personnel who will be looking inside it. (Um, actually there will be just one, the guy who freaking designed and built the whole thing. But I digress...) The box, DIN rail, and ferrite cores were from Digi-Key, and the disconnect switches from some outfit I found online. Very reasonably priced, and they disconnect both positive and negative as required by NEC (and common sense).
The ferrite cores are part of my indulging an apocalyptic fantasy about surviving an EMP attack. (Don't judge...) Between the 150+ feet of ferrous metal conduit, which represents a waveguide below cutoff at EMP E1 pulse frequencies, the very lossy RF transmission line represented by the tray cable, the 150 Ohms or so of RF impedance from the ferrites, and my surge protection devices, I feel pretty confident that my PV array will not act as an antenna to fry my equipment from outside my big ugly Faraday cage.
IMG_2728.jpg
The MATE3 showing that the thing can produce power, along with an Ethernet switch and home-built Raspberry Pi computer. Those latter items are powered via 12 V stepped down from the big battery with a DC-DC power supply (all parts from DigiKey). Of course there is a properly sized fuse protecting the wiring to the DC-DC supply.
The two charge controllers, the MATE3, and my computer are accessible to me via TCP/IP.
The terminal strip is currently just attached to one control circuit feeding a solid-state relay that feeds my chest freezer. It's a load that can be turned off at night if I wind up off-grid for any length of time--essentially a thermal battery. The relay control comes from the Outback Radian's AUX output in "load shed" mode.
IMG_2719.jpg
The Outback GSLC is a rather cozy little space to do wiring in. But it does provide everything you need, and lots of knockouts wherever you might need them. I wound up having to remove all the stock wiring and starting over, using the wire segments Outback provided where I could. I didn't use their ground-fault breaker assembly at all, but it cost no more to order the fully loaded GSLC than to buy a bare one along with the parts I did need. Note the HUB mounted on the left, and a Midnite AC surge protector on the AC grid input.
Also note the insulating bushings at various important places. The insulation would be a dangerous mess without them. The NEC actually makes a lot of sense sometimes. I couldn't have done all this without my well-thumbed NEC 2017 paperback edition.
(Due to image attachment limits, continued in a comment below, which hopefully will get approved soon.)
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