Special Systems
Hospital isolated power, solar and batteries, EV charging and other systems with their own rules.
Isolated Power Systems: How Hospitals Protect Wet Procedure Locations
Why operating rooms may use ungrounded “isolated” power with a line isolation monitor instead of GFCIs, and how NEC Article 517 and NFPA 99 handle wet procedure locations.
Read article →3 min readSolar and Batteries in the Code: Articles 690, 705 and 706
A tour of the NEC articles behind home solar and battery systems: rapid shutdown, the 120% busbar rule, and energy storage basics, with a calculator.
Read article →3 min readEV Charging and NEC Article 625
How the code treats electric vehicle charging: continuous load sizing at 125%, individual branch circuits, adjustable chargers and load management. Includes a quick calculator.
Read article →8 min readSizing Backup Power: Watts, kWh, Motor Starting and NEC 702
How to size a generator or home battery for outages and PG&E shutoffs: running watts and starting surge, kW and kWh, altitude derating, and what Article 702 asks for. With two calculators.
Read article →8 min readEV Charger Safety: Why We Recommend Hardwired Over a Plug-In 14-50
Plug-in EV chargers on a NEMA 14-50 receptacle are common, but hours of heavy current are hard on a receptacle. What can go wrong, what the code says about GFCI protection, and why we recommend hardwiring.
Read article →5 min readHome Solar and Batteries in California: How It Works, Net Billing and Sizing
A plain-English guide to home solar and batteries in PG&E territory: how PV and inverters work, the Net Billing Tariff, kW vs kWh sizing with a calculator, the 120% rule, rapid shutdown, PTO, PSPS and incentives as of Nov 2026.
Read article →Local rules decide. These articles explain general ideas and point to the code sections we use. They are not legal or engineering advice and don’t replace the code itself. California adopts the NEC with its own amendments, cities and counties can add more, and the local inspector (the AHJ, or authority having jurisdiction) has the final say on any job. Read the code free at NFPA’s free access page.