Packard PRMJ21 Start Capacitor

When you are troubleshooting a motor that won't kick over or is just humming on start-up, the Packard PRMJ21 Start Capacitor is a reliable solution for restoring high starting torque. This 21-25 MFD 330V Round Start Capacitor is engineered for intermittent AC duty, specifically designed to stay in the circuit for a 3-second start cycle to boost the compressor or motor up to 75% of its rated speed. Field-tested for heavy-duty HVACR applications, it features a moisture and oil-resistant phenolic resin case that protects the internal dry electrolytic components from the harsh environments common in mechanical rooms. This capacitor replaces Mars 11955, Supco CS21-25X330, and Global 1055 with a standard 1-7/16" diameter for easy mounting. With a 330 VAC rating, it providing a significant safety margin for 240V systems, ensuring the dielectric can handle voltage transients without premature failure. The dual blade terminals allow for quick, secure wiring during emergency service calls.

• Universal Compatibility: Direct physical and electrical replacement for industry-standard part numbers like Mars 11955 and Supco CS21-25X330.
• Rugged Housing: The molded plastic resin case prevents failure due to oil exposure or high humidity in commercial refrigeration setups.
• Wide Temperature Range: Rated for operation from -40°C to 65°C, maintaining stable microfarad capacitance in both extreme cold and high-heat environments.
• Technical Compliance: Meets EIA RS-463 Type 2 standards for non-polarized motor starting circuits.
• Fast Integration: Standard 1/4 inch male terminals ensure compatibility with existing wiring harnesses without needing new crimps.

Can I use a start capacitor with a higher voltage rating?
Yes. In HVACR service, you can always go up in voltage (e.g., using this 330V capacitor to replace a 250V model), but never down. The voltage rating is the maximum dielectric strength; using a 330V unit on a lower voltage circuit often extends the component's service life.

What happens if my MFD rating is slightly off?
It is critical to stay within the 21-25 uF range specified by the motor manufacturer. Lower capacitance may fail to provide enough torque to break the rotor's inertia, while excessively high capacitance can cause the start windings to overheat during the initiation phase.

How do I know if the start capacitor is bad?
Aside from physical signs like a blown-out header or a pungent smell, technical diagnosis involves checking for a humming motor that fails to rotate or using a multimeter to verify the microfarad (MFD) output is within the 21-25 tolerance. If the motor requires a mechanical "nudge" to start, this capacitor likely needs replacement.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.