Symbols and Wiring Diagrams: Three-Phase Motor Wiring Diagrams

 

Step-by-Step Breakdown

1. Fan Operation:

   • Fan On Position:
     • Move the selector switch on the thermostat to the "Fan On" position.
     • This action provides power through terminal two of the terminal to the indoor fan contactor.
     • When the indoor fan contactor coil energizes, its corresponding contacts close, allowing the indoor fan motor (MA fan motor) to start running.

2. Cooling Operation:

   • Cooling Position:
     • Move the selector switch to the "Cooling" position on the thermostat.
     • Make the thermostat call for cooling.
     • The thermostat sends a signal that energizes a coil (typically shown in red in the diagram).
     • When this coil energizes, it closes its corresponding contacts, starting the cooling process.

3. Compressor Operation:

   • The compressor starts when the thermostat closes the circuit between terminals.
   • When the contactor coil energizes, it closes its corresponding contacts, allowing the compressor to start.
   • This is also accompanied by a set of normally closed contacts, which ensure that the compressor starts and operates correctly.

Key Components and Their Functions

• Selector Switch:

  • Allows switching between different modes (Fan On, Cooling).

• Thermostat:

  • Sends signals to start the cooling process and fan operation.

• Contactors and Coils:

  • When energized, they close their corresponding contacts to complete circuits for the fan and compressor operations.

• MA Fan Motor:

  • The indoor fan motor, responsible for circulating air inside.

• EX Motor:

  • The exhaust motor, typically involved in venting air.

• Compressor:

  • Starts when its contactor coil energizes, crucial for the cooling process.

Diagram Interpretation

• Terminals and Contacts:
  • Terminal numbers indicate specific points where connections are made.
  • Contacts associated with coils show how circuits are completed when coils are energized.
• Flow of Operation:
  • Power flows through various terminals and contacts to initiate fan and cooling operations.
  • The process involves closing and opening of specific contacts based on the thermostat's signals.

Example of Operation Flow:

1. Fan On:

   • Thermostat in "Fan On" position → Terminal 2 energized → Indoor fan contactor coil energizes → Fan motor starts.

2. Cooling:

   • Thermostat in "Cooling" position → Cooling call initiated → Coil energizes (red outline) → Contacts close → Compressor starts.