Code Compliant Conductor Sizing: a 2021 take on a 2011 SolarPro Article

• January 13th, 2021
One of the most difficult things to do with the NEC, is to understand how to use it to properly size wires. You can get 10 of the top experts in the world in a room and if you talk about how to properly size a wire, you can be sure there will be exciting conversations (disagreements). The best article I ever read on the subject was in the now retired SolarPro Magazine, where you can still access old articles at May SolarPro someday be resurrected!
Wire sizing is very uniform throughout the NEC, so if you truly understand this article, you will be able to wire size about anything, including an energy storage system or a circuit to an air conditioner on the roof.
As I read this article that is based on the 2011 NEC, I make comments and update how to comply with the 2020 NEC. A few differences are that we no longer have 1A fuse increments below 15A (we skip from 10A to 15A now) and we no longer derate for conduit in sunlight on a rooftop.
Warning: This information is difficult, so do not expect to understand it in a day. You are welcome to skip this podcast, or you can do what I did when I first read NEC Article 690. I did not understand it, but got familiar with it and the terminology and after reading it 1000 times or so, I wrote some books on it.
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PV Safety Basics Part 2

• December 30th, 2020

The most misunderstood PV label (“terminals on line and load side may be energized in the open position”), DC and AC disconnects, Capacitors, PV is on when the Sun is up, Pocket Voltage Indicator, Hot Stick Voltage Detectors (only work with alternating current), Lockout Tagout (LOTO), Material Safety Data Sheets (MSDS), 6-feet = Fall Protection, Guardrail Fall Protection, Safety Net Fall Protection, Personal Fall Arrest Systems (PFAS), Anchor, Harness, Lifeline, Shock Absorbing Lanyard, Ladders Safety, Fiberglass vs. Aluminum Ladders, Working Around Power Lines, 3 points of contact, Tool Backpack, Yoyo (self-retracting lifeline) and Sun Exposure!

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PV Safety Basics Part 1

• December 23rd, 2020

NEC, too much current on a wire, OSHA (Occupational Safety and Health Administration) for employees, NFPA, Battery Bank Locations, AHJ (Authority Having Jurisdiction), NABCEP, Hydrogen and Ventilation with Lead-Acid Batteries, Guarding Live Parts, Working Spaces NEC 110.26, Panelboards, Personal Protective Equipment (PPE), Fall Protection, Arc-Flash Protection, Skylights, Ergonomics, Staging, Preventing Lumbar Disc Injuries, Volt Meter Testing, First Aid Kits and Eye Wash Stations.

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PV Markets and Applications Part 3

• December 16th, 2020

AC-Modules, Direct PV Systems, Water Pumping with PV, Self-Regulating PV, Hybrid PV Systems vs. Hybrid Inverters, Solar Living Institute (RIP), Pumped Hydro Storage, Utility Scale Solar Farms, Large Scale PV Electric Supply Stations (NEC 691), PV Feed-in-Tariff’s, NexTracker Single Axis Trackers, Distributed Generation (DG), NABCEP, Community Solar, Community Choice Aggregation (CCAs), SEIA Houses per MW, 6kW per house average, Energy Efficiency, Resistance Heater 100% efficiency vs. Heat Pumps that are 3x better than 100%, Spectrolab Space Solar.

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PV Markets and Applications Part 2

• December 9th, 2020

Utility Interactive PV Systems, Direct Current, Alternating Current, 5-minute UL 1741 anti-islanding requirements, PV the anti-load, net-metering, residential and commercial voltages, 120/240V, 120/208V, 277/480V, Delta, Stinger, Medium Voltage, High Voltage and Ultra High Voltage Connections, Nikola Tesla, Utility Scale PV, NEC Article 691, Charge Controllers, Stand-alone (off-grid), Rectifier (ac-to-dc), Tesla Powerwall, AC-Coupled PV, DC-Coupled PV and SolarEdge.


Stay tuned for Part 3 of PV Markets and Applications Next Week!

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PV Markets and Applications Part 1

• December 2nd, 2020

PV Markets and Applications, Grid-Tied PV with and without Batteries, Voltage Sags and Peaks, California Rule 21, Energy Storage, Smart Electronics, Bidirectional EVs, UL 1741, UL 1703, CE, NEC, Anti-islanding, Stand-alone, Multimode Inverters, Microgrid Interconnect Device (MID), Interactive Inverter, Solar in Space, Space Based Solar Power (SBSP), Portable Solar Power, Hybrid, Utility Scale PV, Distributed Generation (DG), Concentrated PV, Concentrated Solar Thermal, Solar Thermal vs. Solar PV. Stay tuned for Markets and Applications Part 2 of 3 next week!

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History, Present and Future of Solar PV

• November 25th, 2020

PV Markets and Applications, NABCEP Exam, Edmund Becquerel, Photovoltaic Effect, Einstein’s Photoelectric Effect, PV Flash Testing, Bell Labs, Vanguard 1 Satellite, World Installed Capacity of PV, 1 TW of PV Installed, Hockey Stick PV Growth, Space Based Solar Power (SBSP), Dyson Sphere, Swanson’s Law, PV $77/watt in 1977, Solar PV and Eclipses, Guerrilla Solar and Perpetual Solar Flight with the Solar Impulse.

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Comparing Battery Technologies

• November 18th, 2020

What makes different battery technologies better for different applications, primary and secondary batteries, state of charge (SOC) vs. depth of discharge (DOD), voltage vs. charge, battery open circuit voltage, battery internal resistance, lithium vs. lead acid, battery nominal voltage, 3.6V, 3.2V and 2V, cycle life factors, energy per weight, energy per volume, power per weight vs. energy, arbitrage, self consumption, max discharge current vs. continuous current, charge voltage vs. nominal voltage vs. float voltage, BMS,  algorithms,  NiMH, NiCad, recycling batteries.

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2020 NEC Article 705 Interconnected Power Production Systems from an Energy Storage System (ESS) perspective

• November 11th, 2020

Article 705 applies to PV and ESS. Everything we say here is going to apply to anything backfeeding the grid or a microgrid, however we will use ESS examples. We cover anti-islanding, Microgrid Interconnect Devices (MID), IEEE, Microgrid System definition, 705.11 Supply-Side Connections, 705.12 Load-Side Connections, 705.13 Power Control Systems (PCS), Article 705 Part 2 AC Microgrids.

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Energy Storage relevant material in the 2020 NEC, Chapter 6 Special Equipment, Chapter 7 Special Conditions, Chapter 8 Communication Systems, Chapter 9 Tables

• November 4th, 2020

In this podcast we cover material in Chapters 6 & 7 in the NEC (not including 706 ESS in detail, which we covered in a previous podcast) from an ESS point of view, including 625 EV Power Transfer Systems, EVSE=EV supply equipment, 692 Fuel Cells, 702 Standby Systems, ATS (automatic transfer switch), MID (microgrid interconnect device), 705 Interconnected Power Production Sources, 706 Energy Storage Systems (ESS), 710 Stand-Alone Systems, 712 DC Microgrids, 750 Energy Management Systems, Power Control Systems, Chapter 8 Communication Systems, Chapter 9 Tables, Conduit Fill Tables, Voltage Drop Tables.

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