CEA Reading Electrical Blueprints 3 — Questions and Answers
Question 1: On an electrical blueprint, 'EMT' in a conduit note refers to:
- Electrical Metallic Tubing (Correct answer)
- Emergency Transfer
- Encased Metal Tray
- External Metal Terminal
Correct answer: Electrical Metallic Tubing
EMT stands for Electrical Metallic Tubing, a thin-wall metal conduit commonly specified on commercial drawings.
Question 2: A blueprint note reads '3-#12 AWG in ¾" EMT.' How many conductors are in this conduit?
- 1
- 2
- 3 (Correct answer)
- 4
Correct answer: 3
The '3' prefix indicates three individual conductors—typically two hots and a neutral, or two hots plus a ground.
Question 3: On a single-line diagram, a diagonal line through a conductor symbol indicates:
- The conductor is grounded
- The number of conductors in that run (Correct answer)
- A conduit expansion joint
- A neutral conductor
Correct answer: The number of conductors in that run
Diagonal tick marks across a single line indicate the number of conductors bundled in that run.
Question 4: What does the abbreviation 'MLO' mean in a panel schedule on blueprints?
- Main Lugs Only (Correct answer)
- Maximum Load Output
- Multi-Line Override
- Main Line Opening
Correct answer: Main Lugs Only
MLO means Main Lugs Only, indicating a panelboard without a main circuit breaker—fed from an upstream device.
Question 5: Which scale is MOST commonly used for electrical floor plans in commercial construction?
- 1/16" = 1'-0"
- 1/8" = 1'-0"
- 1" = 1'-0"
- 1/4" = 1'-0" (Correct answer)
Correct answer: 1/4" = 1'-0"
1/4" = 1'-0" is the most common scale for commercial electrical floor plans, providing enough detail while fitting on standard sheets.
Question 6: On a blueprint, 'GFI' or 'GFCI' next to a receptacle symbol means the device:
- Is on a dedicated circuit
- Has ground fault circuit interrupter protection (Correct answer)
- Is rated for 20 amperes only
- Is installed in a weatherproof enclosure
Correct answer: Has ground fault circuit interrupter protection
GFCI indicates the receptacle includes ground-fault circuit-interrupter protection, required in wet or damp locations.
Question 7: A blueprint detail showing conduit bending radius requirements is MOST likely found in:
- The architectural floor plan
- The electrical specifications or detail sheets (Correct answer)
- The mechanical plan
- The site plan
Correct answer: The electrical specifications or detail sheets
Conduit bending and installation details are specified in the electrical specification sections or dedicated electrical detail sheets.
CEA Reading Electrical Blueprints 3
On an electrical blueprint, 'EMT' in a conduit note refers to: