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How to Know if your AC Circuit Breaker or Fuse is Correct


By Dave Rongey - Summary:

How to Troubleshoot and Fix the Most Common Air Conditioner Problems: Guide to Air Conditioner Specifications and AC Unit Troubleshooting.


Guide to Air Conditioner Specifications and Troubleshooting

Electrical Question: The buyers of my home want me to call out an electrician to fix a problem with the air conditioning.

  • The electric circuit panel has had a 50 amp circuit breaker and the air conditioning unit has not been change in over ten years.
  • I’m afraid that if I install a 20 amp circuit breaker it will constantly trip, and then I’ll have another problem and will have wasted a service call out fee.
  • Is there something I could tell the potential buyers or am I wrong and the ac circuit set up has been incorrect all these years.
  • See below for the part of inspection report that explains the problem.

Here is the wording from the Home Inspection Report

  • Observed that the circuit breaker for AC unit is over sized (50 amp).
  • The air conditioner specification plate calls for maximum breaker size of 20 amp.
  • An over sized circuit breaker could result in damage to AC unit and or electrical wiring.
  • In need of evaluation and repair by qualified electrician.

This home electrical repairs question came from: Tracy, from Dallas, Texas.

See more about Home Electrical Repairs for Texas

Dave’s Reply:
Thanks for your electrical repair question Tracy.

  • AC Units and a Home Sale or Purchase
    • When a home is for sale it is in the best interest of the buyer to know that all of the equipment installed at the home has been installed correctly and that the devices are functioning properly, otherwise repairs must be made or agreements about how to handle the situation.
    • One option for some optional equipment may be to remove the unit completely, however this too should be done by a qualified professional.

Properly Sizing an Air Conditioning Circuit

  • The Importance of the Air Conditioner Specification Plate
    • The air conditioner specification nameplate describes the maximum circuit breaker size that is allowed for that AC Unit.
    • As indicated in the home inspection report, the correct circuit size is intended to protect the AC Unit and the electrical wiring and components.

How to Troubleshoot and Fix the Most Common Air Conditioner Problems

  • Check the Circuit Size
    • Verify that the correct circuit wiring and breaker has been installed as described by the AC Unit Specification Nameplate.
  • Check the Disconnect Switch
    • The air conditioner should have a service disconnect mounted near the unit. If the disconnect is equipped with fuses or a circuit breaker then verify that the size of the fuse or breaker is correct as well.
  • Tripping Circuit Breaker When the AC is Not Running
    • If the circuit for the AC Unit trips the circuit OFF when the unit is NOT running then there is a problem with the electrical circuit or HVAC control wiring.
  • Tripping Circuit Breaker When the AC Is Running
    • If the circuit trips OFF while the AC Unit is running then there may be a start or run capacitor that is faulty and needs to be replaced.
    • Low levels of freon coolant will cause an AC unit to stop running to prevent damage to the unit. Freon levels should be checked and recharged as needed by an AC Service Technician.
    • Internal problems with the AC unit are best identified and repaired by a qualified AC Technician.
  • Check the Area of the Air Conditioner
    • Be sure the air conditioner is well maintained and free or debris and plant growth.
    • The aluminum fins of the condensing coils located around the AC enclosure should be clean and clear to allow air flow for proper cooling.
    • The top of the AC unit where the fan grill is located should be clear and unobstructed to maintain air flow.
  • Check the Thermostat
    • Check the thermostat to make sure it is working normally or has a display.
    • Be sure the thermostat is set to the Cooling Mode and the temperature settings are correct.
    • Replace the battery if needed.
    • NOTE: Typically the low voltage power for the thermostat comes from a power supply located within the furnace or blower unit (see below).
  • Check the Home Heating and Air Conditioning HVAC System
    • The Home HVAC System may have more than one component, and each of these components should be checked to ensure proper operation: Furnace, Blower Unit, Thermostat, Air Conditioner Unit.
    • Verify the circuit power to main heating and air condition blower unit. If the main blower unit is not functioning then the ac unit will cycle off.

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FAQs Frequently Asked Questions and Comments

One Response to “How to Know if your AC Circuit Breaker or Fuse is Correct”
  1. Ac Repair In Dallas Tx says:

    Thanks for your tips. They actually came in handy on a job I was doing.


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