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Owned by Todd

From first-year apprentice to seasoned journeyman — NEC-based training for every level. State exam prep included. The Junction Box has you covered.

57 contributions to The Junction Box
⚡ Trade Knowledge — What Does That Motion Detector See? ⚡
You walk into a room protected by a passive infrared (PIR) motion detector, and it detects your movement. What is the PIR sensor actually detecting? A. Sound waves bouncing off your body. B. Changes in infrared energy across its detection zones as you move. C. A change in air pressure when you enter the room. D. A magnetic field created by your movement. Drop your choice in the comments. New to alarm systems? Take a guess. That’s how we learn. We’ll reveal the answer and explanation in a couple of days. 👀
⚡ Trade Knowledge — What Does That Motion Detector See? ⚡
⚡ Check Your Knowledge: Working Space ⚡
You're installing a 20-inch-wide, 120/240V panelboard in a dwelling garage. Per the NEC, what's the minimum width of the clear working space in front of it? A. 20 inches B. 24 inches C. 30 inches D. 36 inches 👇 What's your answer, and why? Bonus: How deep does that working space have to be, and what's the minimum height? Answer reveal in a couple of days.
1 like • 3d
⚡ Check Your Knowledge: Answer Reveal! ⚡ Answer: C. 30 inches. Why: NEC 110.26(A)(2) says the working space in front of electrical equipment must be the width of the equipment or 30 inches, whichever is greater. The panel here is only 20 inches wide, so the 30-inch minimum wins. The space doesn't have to be centered on the panel, but the equipment doors must be able to open at least 90°. Why not the others: A (20 in.): That's the panel width. It only controls when the equipment is wider than 30 inches. B (24 in.): That's the entrance/egress width for large equipment (1200 A or more, over 6 ft wide). It isn't the working space width. D (36 in.): That's the working space depth for a 120/240V panel, not the width. Bonus answers: Depth: 3 feet (Table 110.26(A)(1), 0-150V to ground). Height: 6.5 feet or the height of the equipment, whichever is greater (110.26(A)(3)). Takeaway: Working space is a box: 30" wide, 3' deep, 6.5' tall at minimum for a typical residential panel. Don't store anything in it, because it needs to stay clear. Great job to everyone who played along!
⚡ Electrical in the Wild 🌴 — Hawaii Edition!
Can you legally mount electrical conduit and lighting on a living tree? While vacationing in Hawaii, I spotted this installation on a palm tree right next to the beach. Naturally, the electrician in me had to stop and take a picture! At first glance, you might think this is a code violation. But is it? 🌴 NEC 410.36(G) — Trees Here's something that might surprise you! The NEC actually permits outdoor luminaires and associated equipment to be supported by trees. That's right! Mounting lighting equipment on a living tree is not automatically a code violation. However, there are still other requirements to consider. 🔧 NEC 300.11(A) — Securing and Supporting Raceways and electrical equipment must be properly secured and supported. The installation must account for the tree's movement and growth without damaging the electrical system. ⚡ NEC 225.26 — Vegetation as Support Trees cannot be used to support overhead conductor spans. That's an important distinction between mounting a luminaire on a tree and using a tree to support overhead wiring. 🌧️ NEC 314.15 — Damp or Wet Locations Electrical boxes and fittings exposed to weather must be suitable for the environment and installed to prevent moisture from entering or accumulating. 🌊 NEC 300.6 — Protection Against Corrosion Being right next to the ocean means salt air and moisture are major considerations. Metallic raceways, fittings, and supports must be adequately protected against corrosion. --- 💡 So, is this installation code compliant? Possibly! The NEC permits tree-mounted lighting, but the entire installation still needs to meet applicable wiring and equipment requirements. Now here's my question for the community: 👷 Would you have thought mounting conduit and lighting on a palm tree was allowed? And looking at this picture, do you see anything else worth questioning? Drop your thoughts and code references below! ⚡ The Junction Box — Connecting Electrical Concepts.
⚡ Electrical in the Wild 🌴 — Hawaii Edition!
⚡ Check Your Knowledge: Small Conductor Overcurrent Protection ⚡
You’re running a general-purpose branch circuit with 12 AWG copper conductors. Per the NEC small conductor rule, what’s the maximum overcurrent protection allowed? A. 15 amps B. 20 amps C. 25 amps D. 30 amps 👇 What’s your answer, and why? Bonus: What’s the max overcurrent protection for 14 AWG copper? What about 10 AWG? Answer reveal tomorrow! ⚡
⚡ Check Your Knowledge: Small Conductor Overcurrent Protection ⚡
1 like • 4d
⚡ Check Your Knowledge: Answer Reveal! ⚡ Answer: B. 20 amps. Why: NEC 240.4(D) is the small conductor rule. It caps the overcurrent protection for the smallest copper conductors, no matter what the ampacity tables say: 14 AWG copper: 15 A 12 AWG copper: 20 A 10 AWG copper: 30 A Why not the others: A (15 A): That's the limit for 14 AWG, not 12. C (25 A): 12 AWG copper is listed at 25 A in the 75°C column, but 240.4(D) overrides it. D (30 A): The 90°C column shows 30 A for 12 AWG, but that column is only for derating, not for sizing the breaker. Bonus answers: 14 AWG = 15 A, 10 AWG = 30 A. Takeaway: Don't read the ampacity table and stop. The small conductor rule is the ceiling for 14, 12, and 10 AWG, so a 12 AWG circuit never gets a breaker bigger than 20 A.
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Todd Daugherty
4
13 points to level up
@todd-daugherty-2603
Former Naval Electrician’s Mate, 20+ years Electrical Contractor and Credentialed CTE Instructor. "Teaching what works"

Active 9h ago
Joined Jun 7, 2026