Lecture Notes: Wiring Diagrams for HVAC Systems

Overview

• Focus on wiring diagrams for HVAC systems.
• Explanation of the flow and connections for various components.

Key Components and Circuits

Line 1 and Line 2

• Line 1:
  • Enters a switch.
  • Connects to a heat element.
  • Returns to Line 2.
• Line 2:
  • Similar setup with a switch, heat element, and connection to Line 1.

Inductive Load and Fan Motor

• Line 1 connects to a switch.
• From the switch to an inductive load or fan motor.
• Returns to Line 2.

Transformer and Thermostat

• Power to the transformer then home to Line 2.
• Connection through a fuse into the thermostat.
• Thermostat handles low voltage work, connecting R to W.
• Heat Relays (HR):
  • HR1 and HR2 distinguish low voltage load control for high voltage switches.

Fan Relay (FR)

• Energizing G for indoor fan relay.

Outdoor Unit Circuit

• Separate Line 1 for outdoor unit.
• Switch to compressor and condenser fan motor.
• Compressor Contactor (CC):
  • Low voltage load signal connection.
  • Y stands for compressor contactor.

Wiring Process

Steps to Wire the System

• Highlighting Wires:
  • Each wire traced and highlighted in the diagram for clarity.
• Sequencers:
  • Used to control heat elements.
• Fan Relay Wiring:
  • Short on terminals solved by utilizing extra terminal spots.

Powering the Transformer

• High voltage wiring into transformer and fuse.
• Connection to R terminal of the thermostat.

Low Voltage Work

• Connecting thermostat W wire to heat relay for low voltage work.
• Wiring for common home and sequence for energizing heaters.
• Connection adjustments for fan relay and compressor contactor.

Outdoor Unit High Voltage Wiring

• Separate circuit for outdoor unit.
• Line 1 into contactor, out to compressor and fan motor.

Testing and Operation

System Power Up

• Thermostat Controls:
  • Cooling, fan, and heating controls.
• Voltage Checks:
  • Voltage readings for sequencers and elements.

Sequencer Functionality

• Sequencers cause delay in element activation to manage amperage load.

Final Adjustments

• Ensuring fan operation with heat elements through normally closed relay setup.
• Sequence adjusted for fan relay and element synchronization.

Complete Wiring Diagram Summary

• Basic model with two heat elements.
• Normally closed and open relay configurations.
• Full schematic overview for an AC system.