Quick Hits

📱 EPISODE 2 — Article 242 (Part 2 of 4)

Type 1, 2 & 3 SPD Installation Rules

SLIDE 1 — Where SPDs Can't Go
🚫 USES NOT PERMITTED (242.12)

SPDs are OFF LIMITS in these situations:
❌ Circuits over 1000V AC / 1500V DC — that's surge arrester territory (Part III)
❌ Ungrounded, impedance-grounded, or corner-grounded delta systems — UNLESS the SPD is specifically listed for that use
❌ Any spot where the SPD's voltage rating is less than the max continuous phase-to-ground voltage at that point

Rule of thumb: the SPD has to be rated for the system it's protecting — no shortcuts.

SLIDE 2 — Type 1 & Type 2 Placement
📍 TYPE 1 SPDs (242.13)
Can go pretty much anywhere the manufacturer's instructions allow. If installed at the service, it connects to one of these 4 points:
1️⃣ Grounded service conductor
2️⃣ Grounding electrode conductor
3️⃣ Grounding electrode for the service
4️⃣ Equipment grounding terminal in service equipment

📍 TYPE 2 SPDs (242.14)

Service-supplied building → anywhere on load side of the service disconnect OCPD

Feeder-supplied building → load side of the FIRST OCPD at that structure

Separately derived system → load side of the first OCPD there too

SLIDE 3 — Type 3 SPD Placement
📍 TYPE 3 SPDs (242.16)

These go on the load side of a branch-circuit OCPD, up to the equipment they're protecting.

📏 Key distance rule: IF the manufacturer's instructions call for it, there must be a minimum of 30 ft (10m) of conductor between the Type 3 SPD and the service/separately derived system disconnect.

Why the distance matters: feeder conductors coming from outside are exposed to a rougher surge environment (think lightning-induced transients), so protection gets layered as you move deeper into the system.

SLIDE 4 — Exam Question + CTA
🧠 TEST YOURSELF

Q: A Type 2 SPD is being installed to protect a feeder-supplied structure. Where must it be connected?

A) Anywhere ahead of the service disconnect
B) Load side of the first OCPD at that structure
C) Only at the main service equipment
D) Directly to the grounding electrode only

(Drop your answer below 👇)

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