Low Voltage Systems (C-7) · Lesson 3 of 4

Keeping Low-Voltage, Fire Alarm and Communications Wiring Apart

"Keeping Low-Voltage, Fire Alarm and Communications Wiring Apart" is lesson 3 of 4 in the Low Voltage Systems (C-7) Learning Hub. It opens with "Know Which Circuit Family You Are Pulling" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Know Which Circuit Family You Are Pulling
  2. Class 2 and Class 3: Barrier or Separate Enclosures
  3. Power-Limited Fire Alarm: 2 Inches and the Class 2 Exception
  4. Communications Cable: Indoors and on the Building
  5. Nonpower-Limited Fire Alarm and Class 1 May Share, With Rules

The worked example in the course applies this lesson to a realistic job in 5 steps.

What you'll be able to do

  • Explain the main idea of "Keeping Low-Voltage, Fire Alarm and Communications Wiring Apart" in plain language you can use on the exam.
  • Apply this step with confidence: "Power-Limited Fire Alarm: 2 Inches and the Class 2 Exception".
  • Apply this step with confidence: "Communications Cable: Indoors and on the Building".
  • Apply this step with confidence: "Nonpower-Limited Fire Alarm and Class 1 May Share, With Rules".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Separation Rules: Which Circuits Can Share a Fitting Class 2 cable + 120 V light/power conductors same box, raceway or tray NO - unless a barrier is used 8 CCR §2585.3 Power-limited fire alarm + Class 2 same cable, enclosure or raceway YES - if Class 2 insulation is enough 8 CCR §2586.3(d) Power-limited fire alarm + 120 V power side by side, no barrier 2 in. (50.8 mm) minimum gap 8 CCR §2586.3(c) Indoor communications + 120 V power side by side, no barrier 2 in. (50.8 mm) minimum gap 8 CCR §2587.3(d) Nonpower-limited fire alarm + Class 1 same enclosure, cable or raceway YES - all insulated for highest V 8 CCR §2586.3(a) Gap check: 1.5 in. FAILS the 2 in. rule; move to 2.5 in. and it passes 2 in. = 50.8 mm; 2.5 in. = 63.5 mm Source: 8 CCR §2585.3, §2586.3, §2587.3 (Low-Voltage Electrical Safety Orders) CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Know Which Circuit Family You Are Pulling

Title 8 sorts low-voltage wiring into families: electric light and power; Class 1; nonpower-limited fire alarm (NPLFA); Class 2 and Class 3 remote control, signaling and power-limited circuits; power-limited fire alarm (PLFA); and communications. Every separation rule is a pair of families. 8 CCR §2586.1 says fire alarm circuits are classified as either nonpower limited or power limited, and §2586.4 requires fire alarm circuits to be identified at terminal and junction locations and PLFA circuits to be durably marked as such where plainly visible at terminations.

Step 2: Class 2 and Class 3: Barrier or Separate Enclosures

8 CCR §2585.3: for installations built on or after May 5, 2008, Class 2 and Class 3 conductors may not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway or similar fitting with conductors of electric light, power, Class 1, nonpower-limited fire alarm circuits, or medium power network-powered broadband communications cables, unless a barrier or other equivalent form of protection against contact is used.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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