Run Start Capacitor, Round, 25/7.5 MFD, 440/370

Mars 12779 – Dual Round Run Capacitor, 25/7.5 MFD, 370/440V, Aluminum Case

The Mars 12779 is a dual-rated run capacitor with a capacitance of 25/7.5 microfarads (MFD), engineered for continuous-duty operation in residential and light commercial HVAC systems. Designed for use in permanent split capacitor (PSC) motor circuits, it provides reliable phase shift and voltage stability to both compressor and fan motor windings.

This capacitor features dual voltage capability (370/440 VAC) and a pressure-sensitive interrupter for added operational safety. Its round aluminum canister is compatible with standard mounting brackets, making it a direct-fit replacement in a wide range of condenser and heat pump systems.

Application-Specific Design

The 12779 supports dual-motor applications, typically found in split-system air conditioners and rooftop units. Its dielectric formulation and oil-filled construction meet industry endurance standards for high-cycle environments. This unit simplifies service calls by combining two capacitance values into one component, saving time and reducing field inventory requirements.

Technical Specifications

• Capacitance: 25/7.5 microfarads (MFD) ±6%
• Voltage Rating: 370/440 VAC, 50/60 Hz
• Case Shape: Round aluminum
• Terminals: Dual terminal (C, FAN, HERM) configuration
• Construction: Oil-filled, non-PCB dielectric
• Temperature Range: -40°C to +70°C

Dimensions

• Diameter: Approx. 1.75 inches
• Height: Approx. 3.75 inches (without terminals)

Installation Requirements

The Mars 12779 should be installed by certified HVAC technicians. Verify system voltage and capacitance requirements before replacing. Always discharge the existing capacitor using a resistor-rated tool prior to handling. Use insulated terminals and secure the capacitor in a metal strap or OEM-approved bracket to prevent vibration-induced wear.

Contractor Considerations

Part of the Mars Blue Box series, this capacitor meets EIA-456-A performance standards for endurance and electrical reliability. Its wide voltage tolerance and standardized footprint make it a universal replacement solution for service calls involving failed capacitors in two-motor HVAC systems. Designed for field dependability, this model reduces equipment downtime and supports efficient motor operation over extended service intervals.

Performance Attributes

• ✅ Dual Capacitance Configuration – Combines compressor and fan support into one component
• ✅ 370/440 VAC Rating – Compatible with high- and low-voltage PSC motor circuits
• ✅ UL Recognized – Built and tested in accordance with industry safety standards
• ✅ Interrupter Safety Feature – Disengages internal circuit under overpressure conditions
• ✅ Reliable Field Replacement – Commonly used across a wide range of HVAC manufacturers