Reading Electrical Schematics Training - One-Line, Three-Line and Ladder Diagrams

• Electrical Apprentices
• Industrial Maintenance Electricians
• Maintenance and Multi-Craft Technicians
• HVAC and Refrigeration Technicians
• Instrumentation and Controls Technicians
• Electrical Contractors, Foremen and Estimators
• Facility and Plant Operators
• Junior Electrical Engineers and Engineering Technologists
• Electrical Drafting and Design Staff
• Safety Coordinators Responsible for Lockout/Tagout
• Anyone Enrolled in the EFTI Electrical Apprentice Certificate

Reading Electrical Schematics Course Outline

DAY ONE

DRAWINGS, SYMBOLS AND POWER SYSTEM DIAGRAMS

MODULE 1 – ELECTRICAL DRAWING TYPES AND DRAWING SETS

• Purpose of Electrical Drawings: Design, Construction, Operation, Maintenance and Modification
• Types of Drawings: Block, One-Line, Three-Line, Schematic, Wiring and Layout
• How a Drawing Set Is Organized and Numbered
• Title Blocks, Revision History and "Issued for Construction" Status
• Grid References and Cross-Referencing Between Sheets
• Codes and Standards That Apply: CEC, NEC, NFPA 70E, CSA Z462, NFPA 79

MODULE 2 – SYMBOLS, LEGENDS AND STANDARDS

• Purpose and Content of Drawing Legends
• Standard Symbols: IEEE 315 / CSA Z99 and NEMA Conventions
• International Drawings: IEC 60617 Symbols
• NEMA and IEC Symbol Comparison
• Abbreviations and Manufacturer-Specific Symbols
• Practical Exercise: Symbol Identification on Real Drawings

MODULE 3 – CONTACTS, SWITCHES AND DEVICE FUNCTION NUMBERS

• Shelf State: How Contacts Are Shown on Drawings
• Normally Open and Normally Closed Contacts
• Circuit Breaker a/b Contacts, Truck-Operated (TOC) and Mechanism-Operated (MOC) Contacts
• Control Switches, Selector Switches and Pushbuttons
• IEEE C37.2 Device Function Numbers and Suffixes
• Common Device Numbers: 27, 49, 50/51, 52, 59, 63, 67, 81, 86 and 87

MODULE 4 – READING ONE-LINE DIAGRAMS

• Purpose and Levels of Detail in One-Line Diagrams
• Tracing Power Flow From Utility Service to Loads
• Transformers, Switchgear, MCCs, Panelboards and Generators
• Equipment Ratings, Protective Devices and Relaying Shown on One-Lines
• Normal and Alternate Sources, Tie Breakers and Transfer Switches
• Using the One-Line for Switching and Hazardous Energy Control

MODULE 5 – THREE-LINE DIAGRAMS AND INSTRUMENT TRANSFORMER CIRCUITS

• When and Why Three-Line Diagrams Are Used
• Phase Identification and Transformer Connections
• Current Transformer (CT) and Potential Transformer (PT) Circuits
• Polarity Marks, Ratios and Grounding of Instrument Transformer Circuits
• Metering and Protective Relay Connections
• Relating Three-Line Diagrams to the One-Line

MODULE 6 – WORKSHOP: READING A FACILITY ONE-LINE

• Practical Exercise: Tracing a Complete Facility One-Line
• Identifying Equipment, Ratings and Device Functions
• Locating All Sources of Energy and Points of Isolation
• Developing a Single-Line Diagram From a Site Narrative
• Day 1 Review and Questions

DAY TWO

 CONTROL CIRCUITS, WIRING AND TROUBLESHOOTING

MODULE 7 – LADDER DIAGRAMS AND RELAY LOGIC

• Ladder Diagram Layout: Rails, Rungs and Line Numbers
• Wire Numbering and Terminal Identification
• Contact Cross-Referencing Under Relay Coils
• Control Transformers, Control Fusing and Grounded Control Circuits
• Series (AND) and Parallel (OR) Logic, Seal-In Circuits and Interlocks
• On-Delay and Off-Delay Timers
• Practical Exercise: Sketching a Ladder Rung From a Written Description

MODULE 8 – MOTOR CONTROL CIRCUITS

• Two-Wire and Three-Wire Control
• Start/Stop Stations and Multiple Control Locations
• Forward-Reverse Control With Electrical and Mechanical Interlocks
• Overload Relays and Motor Protection on Drawings
• Motor Termination Diagrams: Six-Lead and Nine-Lead Motors
• Recognizing Reduced-Voltage Starters and VFDs on Drawings

MODULE 9 – CIRCUIT BREAKER CONTROL AND TRANSFER SCHEMES

• Breaker Close and Trip Circuits
• Role of 52a, 52b and Lockout Relay (86) Contacts
• Trip Circuit Monitoring and Indicating Lights
• Automatic Transfer Switch Control Logic
• Main-Tie-Main Transfer Schemes
• Reading Manufacturer Switchgear Wiring Diagrams

MODULE 10 – WIRING DIAGRAMS, PLANS AND SCHEDULES

• Wiring and Connection Diagrams vs Schematics
• Interconnection Diagrams and Terminal Strips
• Site Plans, Floor Plans and Riser Diagrams
• Panel Schedules, Conduit and Cable Schedules
• Checking Schedules Against the CEC and NEC
• Hazardous Area Classification Drawings

MODULE 11 – REAL-WORLD CONTROL APPLICATIONS

• HVAC Control Circuits
• Air Compressor Control
• Pump and Level Control Circuits
• Generator and Transfer Switch Controls
• VFD Control Wiring
• Relay Ladder Logic vs PLC Ladder Logic

MODULE 12 – TROUBLESHOOTING WITH ELECTRICAL DRAWINGS

• A Structured Troubleshooting Method
• Gathering Information: Alarms, Indications and Event Logs
• Voltage Tracing on Ladder Diagrams and the Half-Split Method
• Identifying Hazards and Isolation Points Before Testing
• When the Drawings Are Wrong: Red-Lines and As-Built Updates
• Capstone Exercise: Finding Faults on Real Control Schematics
• Course Review, Final Test and Questions

COURSE TIMETABLE

Both Days

Start: 10:00 a.m. Eastern
Finish: 4:30 p.m. Eastern