Quick Hits

🚨 ARTICLE 242: OVERVOLTAGE PROTECTION 🚨
NEC Chapter 2 continues...

This article is all about protecting your system from voltage spikes — think lightning strikes and switching surges. It's split into two lanes:
⚡ Part II → Surge-Protective Devices (SPDs) for systems 1000V AC / 1500V DC and under
⚡ Part III → Surge Arresters for systems OVER 1000V

Same protection concept, different voltage class, different device name. Let's break it down 👇

SLIDE 2 — SPD Types (Part II Basics)
📍 WHERE DO SPDs GO?

SPDs come in "Types" based on WHERE they sit in the system:

🔹 Type 1 — can go on the SUPPLY side of the service/building disconnect (or load side too)
🔹 Type 2 — LOAD side only, connects anywhere past the service disconnect OCPD
🔹 Type 3 — point-of-use, load side of branch-circuit OCPD, must be 30 ft+ of conductor from service (if mfr instructions require it)
🔹 Type 4 — component-level, installed ONLY by the equipment manufacturer

Old-school term alert: Type 2/3 SPDs used to be called TVSS (Transient Voltage Surge Suppressors) — you might still hear that on the job.

SLIDE 3 — Install Rules You Can't Skip
🛠️ KEY INSTALL REQUIREMENTS

✅ SPDs must be listed
✅ Must show they're functioning properly (indicator light/status)
✅ Marked with a short-circuit current rating — can't exceed available fault current (receptacles exempt)
✅ Conductors to the SPD: keep them short, straight, minimal bends — long/bendy leads = higher impedance = weaker protection
✅ Min conductor size: 14 AWG copper / 12 AWG aluminum
✅ NOT allowed on ungrounded/impedance-grounded/corner-grounded systems unless specifically listed for it

🚫 Reconditioned SPDs and surge arresters = NEVER permitted, period.

SLIDE 4 — Exam Question + CTA
🧠 TEST YOURSELF

Q: A Type 3 SPD is being installed at a piece of sensitive electronic equipment. Per the manufacturer's instructions, what minimum conductor distance is required from the service or separately derived system disconnect?

A) 10 ft
B) 20 ft
C) 30 ft
D) No minimum required

(Answer drops in comments 👇 — no cheating!)

📌 We covered Part I & the start of Part II of Article 242 today — next episode we finish out SPD rules and move into Part III (Surge Arresters, over 1000V).

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