When to Use Circuit Breakers for Air Conditioners
By John Karbowski · November 8, 2024
Air conditioners are among the highest-draw electrical loads in any commercial or industrial facility. In Houston's climate, they run for the majority of the year. Properly sized circuit breakers are essential — not just for code compliance, but to protect your HVAC equipment and your building's electrical system.
Why Air Conditioners Need Dedicated Circuits
Every air conditioning unit — from a small split system to a large commercial rooftop unit — must be on a dedicated circuit with properly sized overcurrent protection. Sharing circuits with other loads risks nuisance tripping during compressor start-up (when current draw spikes 3–6 times the running load) and can damage both the AC equipment and other devices on the circuit.
How to Size an AC Circuit Breaker
Check the Equipment Nameplate
Every AC unit has a nameplate with the Minimum Circuit Ampacity (MCA) and Maximum Overcurrent Protection (MOP) ratings. The MCA tells you the minimum wire size needed; the MOP tells you the maximum breaker size allowed.
Size the Breaker to the MOP Rating
The breaker must not exceed the MOP rating on the nameplate. It also must be large enough to handle the starting surge without nuisance tripping. Typically, breakers are sized at 125% of the full-load amperage for AC circuits.
Use the Right Breaker Type
HVAC equipment requires time-delay (dual-element) fuses or breakers that can tolerate the temporary high starting currents without tripping. Standard breakers may nuisance-trip during compressor start-up.
Consider Voltage
Most commercial and industrial AC equipment runs on 208V, 240V, or 480V 3-phase power. Ensure the breaker voltage rating matches your system voltage, and that 3-phase breakers are used for 3-phase equipment.
Signs Your AC Circuit Breaker Is Undersized
- Breaker trips when the AC compressor starts
- Breaker trips during the hottest part of the day when the system works hardest
- AC unit fails to restart after a power interruption
- Breaker feels warm to the touch
- Circuit wiring is warm or shows signs of heat damage
HVAC Electrical Services in Houston
Southern Electrical Services installs and sizes circuits for commercial and industrial HVAC systems throughout Houston. Contact us for a free assessment.