📱 EPISODE 2 — The Annexxed Information Series (Part 2 of 3)

Annex D Calculation Examples & the Administrative Annexes

SLIDE 1 — Annex D: Worked Examples
 

🧮 THE NEC'S OWN HOMEWORK ANSWER KEY

Annex D walks through real load calculations step-by-step — invaluable for anyone studying load calcs:
 

✅ D1–D2: One-family dwelling load calcs (standard AND optional methods)
 

✅ D3: Store building feeder sizing
 

✅ D3(a): Industrial feeders sharing a common raceway
 

✅ D4–D5: Multifamily dwelling calcs (single-phase AND 3-phase)
 

✅ D6: Maximum demand for range loads
 

✅ D7: Sizing dwelling service conductors
 

✅ D8: Motor circuit conductor/overload/short-circuit protection sizing
 

✅ D9–D10: Elevator feeder ampacity (generator field control vs. adjustable speed drive)
 

✅ D11–D12: Mobile home and park trailer calcs
 

✅ D13: Cable tray fill calculations
 

✅ D14: Grounded service conductor sizing examples
 

✅ D15: Load calcs using Power Control Systems (PCS)

📌 If you're prepping for load calc questions on an exam, Annex D is basically a guided practice set straight from the Code itself.

SLIDE 2 — Annex F: Critical Operations Power Systems (COPS) Reliability
 

⚡ AVAILABILITY, RELIABILITY, MAINTAINABILITY

Annex F covers reliability engineering concepts for mission-critical power systems:
 

🔹 Availability = percentage of time a system is functional (MTBF ÷ (MTBF + MTTR))
 

🔹 Even 99.99% availability still means 0.876 hours of downtime per year
 

🔹 Improving existing facility availability: add redundancy, optimize maintenance (RCM), or redesign for higher reliability
 

🔹 Part II covers developing/implementing Functional Performance Tests (FPTs) — the formal testing process before a critical system goes live, including the famous "pull the plug" final test

SLIDE 3 — Annex G: SCADA Systems
 

🖥️ SUPERVISORY CONTROL AND DATA ACQUISITION

Annex G sets recommended practices for SCADA systems monitoring critical loads:

✅ Must be SEPARATE from building management SCADA
 

✅ No single point of failure allowed
 

✅ Redundant system in warm/hot standby
 

✅ DC battery power supply, 24–125V, 72-hour capacity — SEPARATE from other system batteries
 

✅ SPD required at power supply line-side terminals (per Article 242 Part II)
 

✅ Physical security, environmental protection, fire protection (dry agent or double-interlocked preaction) requirements
 

✅ No outside network connection without encryption or fiber optics

SLIDE 4 — Annex H: Administration & Enforcement (Including Article 80!) + Exam Question
 

⚖️ DID YOU KNOW THERE'S AN ARTICLE 80?

Annex H is a TEMPLATE jurisdictions can adopt (verbatim or amended) to administer electrical inspection programs — and it's built AROUND Article 80, which most electricians never think about because it's optional and jurisdiction-dependent!

Article 80 covers:
 

✅ Inspection processes, permits, plan review
 

✅ Definitions: Authority Having Jurisdiction, Chief Electrical Inspector, Electrical Inspector
 

✅ New vs. existing installation rules — existing installations generally grandfathered UNLESS deemed an imminent danger
 

✅ Electrical Board structure, appeals process, inspector qualifications
✅ Violation notices, penalties, disconnection authority

📌 Article 80 ONLY applies if a local jurisdiction specifically ADOPTS it (80.5) — that's why most electricians never interact with it directly; local building codes typically handle this instead.

🧠 TEST YOURSELF

Q: Per 80.9(B), what happens to existing electrical installations that don't comply with a newly adopted edition of the NEC?

A) They must be immediately brought up to code
 

B) They can continue in use unless the AHJ determines they present an imminent danger
 

C) They are automatically grandfathered forever with no exceptions
 

D) They must be inspected annually

(Drop your answer 👇)

FOLLOW — Part 3 wraps up Annexes I, K, and L (the 2029 NEC reorganization preview) ⚡ #JoshTheSparky #NEC2026 #ElectricianLife