HVAC Condenser Fan Motor and Compressor Wiring

Condenser Fan Motor

• Components:

  • Condenser unit with a fan motor typically has three wires: common, start, and run.
  • Schematic: Orange (common), usually brown for start winding but can be purple.

• Wiring Details:

  • Common wire connects to the opposite side of the contactor.
  • Start and run windings are powered by the same leg.
  • Capacitor is powered by the same leg that powers the run winding.
  • Output of the capacitor powers the start winding.

Compressor Wiring

• Components:

  • Also a motor with three terminals: common, start, and run.

• Wiring Details:

  • The same leg powering the run winding of the fan motor powers the compressor run winding.
  • Common wires (C) are connected to the opposite ends.
  • Capacitor output powers the compressor start winding.

Dual Run Capacitors

• Explanation:

  • Dual run capacitors combine two capacitors in one housing with three terminals: C (common), Herm (compressor start winding), and Fan (fan motor start winding).

• Advantages:

  • Saves space.
  • Power distribution is internal, eliminating external jumper wires.

Wiring Diagrams

• Ladder Diagrams:

  • Show line 1 and line 2 powering contactors.
  • Indicate connections of run and start windings through capacitors.

• Component Representation:

  • Run winding: Short and low resistance.
  • Start winding: Long and high resistance.
  • Common (C) is opposite of the run and start connections.

Mounting Capacitors

• Proper Installation:
  • Should be mounted metal to metal to ground.
  • Avoid loose electrical connections.
  • Secure to prevent vibrations.
  • Preferably keep capacitors upright to utilize cooling oil efficiently.

Capacitor Manufacturing

• Preference:

  • Prefer capacitors made in the USA due to stricter regulations.
  • Quality oil and dielectric materials prolong capacitor life.

• Common Issues:

  • Heat and high loads are the common causes of failure.
  • Ensure installation with correct microfarad values and VAC ratings.

Maintenance and Replacement

• Warranty Considerations:

  • If under warranty, use specified parts for replacement.
  • Out of warranty, two individual capacitors are preferred for better cooling and longevity.

• Stocking Capacitors:

  • Stock individual capacitors instead of dual runs for flexibility.
  • Dual-run capacitors can replace multiple combinations but are more costly.

• Common Capacitor Ratings:

  • Microfarad ratings for fan motors and compressors vary.
  • 440 VAC capacitors are recommended for better durability.

Safety and Best Practices

• Avoid Using Tape:

  • Avoid electrical tape on connections, it can cause failures.

• Mounting Inside Electrical Box:

  • Protects from weather and potential water damage.

• Checking for Obstructions:

  • Ensure mounting screws do not hit critical components like copper tubing.