Cedars HVAC Supply stocks run and start HVAC capacitors across a full range of MFD ratings and voltage classes, so you finish the repair today. A failed capacitor is one of the most common causes of HVAC system breakdowns — and one of the fastest repairs a technician can make when the right part is on hand.
Run Capacitors vs. Start Capacitors
Understanding the difference between capacitor types is essential for accurate diagnosis and replacement:
- Run capacitors — Stay in the circuit continuously while the motor operates, providing the phase shift needed to keep single-phase motors running efficiently. Found on compressors, condenser fan motors, and blower motors.
- Start capacitors — Provide an extra boost of torque during motor startup, then drop out of the circuit once the motor reaches operating speed. Used in hard-start applications or systems with voltage drop issues.
- Dual run capacitors — A single capacitor housing two capacitors in one can, typically serving both the compressor and the condenser fan motor simultaneously. Common in residential split systems.
MFD and Voltage Ratings
Capacitors are rated by capacitance in microfarads (MFD or µF) and by voltage. Common voltage ratings include 370V and 440V; a 440V capacitor can safely replace a 370V unit of the same MFD rating in most applications. Never replace a capacitor with a lower voltage rating than what the equipment specifies. MFD tolerance should be within ±6% of the original spec — always match MFD as closely as possible.
When to Replace an HVAC Capacitor
Signs of a failing capacitor include the system humming but not starting, the condenser fan spinning slowly or not at all, the unit shutting off shortly after starting, or a visible bulge or oil leak on the capacitor body. Capacitors degrade over time from heat cycling and should be tested at every maintenance visit using a multimeter or dedicated capacitor tester.
Shop HVAC capacitors at Cedars HVAC Supply — free shipping on orders over $99. Questions? Call (305) 850-6693 or visit our contractor pricing page.
