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26 April 2019

CASE STUDY – 2018-2019PV SOLAR – GRID TIE – 4.7 kWWORKSHOP – ROOF MOUNT

A Do-It-Yourselfer Guide - DIY

BACKGROUNDLocation: Rappahannock VA, lat. 38°NThe Workshop, w/shed and greenhouse, was built in 1996. The building is oriented due South with a trussed gable roof, E/W ridge, 27° roof slope, 24’ x 12’ facing south.

THE PV SYSTEM ORDER - 09-26-2018The system was designed to max out the south roof surface. This equates to 14 each 60 cell PV panels.

- PV Panels – Solarworld SW 295 mono crystalline- Inverter – SMA Sunny Boy 5.0 US- Rack – IronRidge XR1000 rails- Vendor – WholeSale Solar

WSS filled the order with a modified kit complete with all hardware, PV modules, DC/AC Inverter, MC4 AWG #10 PV wire, ground wire lugs, AC disconnect, NEC 2017 solar labels, wire clips, etc. Additionally, WWS provides single line PV electric design diagram; IronRidge provides engineer’s structural certification. Both are required to process the building permit. Since the PV panels in stock were in standard count bundles the order included extra panels. The kit included 16 panels.

(The original install included 2 strings of 7 panels to fit available roof surface. The extra 2 panels were boot-legged after commissioning to create 2 strings of 8 panels. More about that later).

BUILDING PERMITPrior to placing the order and applying for the building permit, it is advised to secure approval from your electric utility company for the proposed Grid Tie PV

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system. Our local electric coop, REC, provides information and application forms available online. With well documented PV System and all appropriate boxes checked, approval was granted on the same day as the submittals. Kudos to REC! Kudos to DIY guy!The requirements for residential Building Permit applications vary, but are pretty standard from county to county. Always check with authority having jurisdiction, AHJ. At a minimum, you will need:

- Survey plat of the property with building(s) located.- Architectural plans demonstrating building structure. In this case the

workshop had been permitted, and the original roof truss engineering was pulled from old files.

- Engineering for PV racking frame.- PV Electric Design, NEC 2017 compliant, shows equipment layouts and with

minimum wire sizes, circuit breakers, grounding and conduit.- A separate Electric Permit is required, pulled by a licensed electrician.

INSTALLATIONS Carpenter – PV Installers (2 man crew - 2 days) The roof structure required additional wood roof purlins to secure the IronRidge rails in alignment with PV panel connection points. At the Workshop, we used 2x6s bolted to the roof trusses under the metal roof.

- Day 1, the wood purlins were completed, IronRidge rails were bolted down, and 2 panels installed.

- Day 2, the remaining panels were installed. The positive-negative MC4 wiredconnections between panels are made. The ‘homerun’ wires are prepped

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with MC4 connectors. However, in fail safe condition, they are left unconnected. The PV array is installed, but not energized!

- Focus on wire management. Check panels in series for continuity, 0 ohms. Note to carpenters – Leave your hammer in the toolbox. Check appropriate wrenches and screw guns. All connections are screwed and bolted. As needed, userubber mallets, not nail hammers.RE: PV solar & electric safety. ‘Safety First’

Meanwhile, a qualified person lays out and mounts the SMA inverter. The qualified person oversees design execution related to PV installations per manufacturer specifications and NEC 2017 code.

Electricians (Journeyman & helper, 2 days)The electricians set DC & AC disconnect boxes and run the conduit. The inverter is located inside the Workshop. The disconnect boxes are installed outside for ready emergency access. NEC code check: all PV conduit inside buildingsis electric metallic tubing, EMT. The electricians wire the PV output circuits to the inverter on the DC side, as per plans. It is important to double check polarity of PV output circuits at the inverter, positive to positive, negative to negative. AC power is wired to the electric service panel with specified 220v 30amp circuit breaker.

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In the workshop, the inverter AC output is connected at the workshop sub panel, which in turn is connected to the main 200amp service panel at the house, and to the utility electric meter. The last wire connection(s) are the ‘homeruns’ for PV source circuits. Before connecting the PV panel circuits, make sure the inverter and disconnects are turnedoff. RE: PV solar & electric safety.Energizing the PV system is last after system performance is checked and accepted by the electric utility.

Communication WiringProvide Cat-5 cable from internet router to the inverter for internet performance monitoring. Cable vs. wireless, your choice. The SMA inverter uploads energy production data to cloud storage. Each inverter has a unique IP address which provides real time electric performance. IP address 192.168.1.6

INSPECTIONS - APPROVALS - COMMISSIONING PV Solar Labels - Information and Hazard Warning labels are installed per NEC article 110.21 & 690.13. Our qualified person directs placement of standard labelsspecific to PV solar. Labels need to be in place for system inspections and commissioning. RE: PV solar & electric safety.Lock out–Tag out, LOTO procedures are a requirement to ensure safety for all mechanics and emergency contingencies. Identify all power sources and means to disconnect, turnoff, lock, and label accordingly. Grid-Tie PV electric energy is not emergency power. It is an electric generating facility. Achieving Grid-Tie certifies the owner as a net metering member that the system is in compliance with all AHJs.

Inspections First, call for county building inspection approval(s).

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Second, submit county final inspection report to the electric utility, requesting grid-tie approval. The utility technician checks the system, measuring voltage and amperage. The inverter is test started to confirm inputs/outputs. With everything OK’d, the utility technician installs the new digital ‘net-meter’. Third, system complete. REC registers the PV energy system with the VA State Corporate Commission.

LESSONS LEARNED - Work with qualified tradesmen.- Read and comply with plans and specifications to high degree. - Hold ‘tool box’ meeting(s) to review effective installation means and methods

procedures. Discuss tools, fasteners, wire management, etc.- Winter kick off a new PV solar system is not the best time, with weather and

short day insolation.- The system is performing as designed, meeting 50%+ of historical electric

load for Feb. - Payback ROI – Our calculations demonstrate an 8-10 year breakeven point

with another 10 years free energy. PV provides security against rising energy costs. The biggest ROI variable is utility rate increases projected at 5% per year.

FULL DISCLOSUREThis ‘Do-It-Yourselfer’ is no amateur. Concurrent with the Workshop PV installation, this qualified person was enrolled in Solar Energy International, SEI’s, PVOL 202 Advanced Solar PV System Design, with successful completion on Feb. 24, 2019.The PV Workshop was successfully commissioned by REC on Jan. 16, 2019. You could say, ‘The horse was chasing the cart’?

WHAT IS YOUR PV ELECTRIC POTENTIAL?Review your monthly electric utility bill. It contains a lot of useful information about your energy use. It is helpful in sizing your own PV solar system. Send us a copy of your electric bill for free appraisal. It helps to have clear sky access for the sun.

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