If your old part reads 40+5 MFD and 370V or 440V, you need a matching dual run capacitor. You can choose a round or oval shape based on the mounting bracket in your outdoor unit.
Parts with these numbers
40+5 MFD 440/370V Round Dual Run Capacitor (Bluefin CPDRR1-405)
40+5 MFD 440/370V Round Dual Run Capacitor (Titan Pro TRCFD405)
40+5 MFD 440/370V Oval Dual Run Capacitor (Titan Pro TOCFD405)
- µF (MFD): must be the same, like 45/5
- Volts: same or higher (440 can replace 370)
- Shape: round or oval, to fit the bracket
What the 40/5 MFD and 440/370V Numbers Mean
The numbers on the capacitor label show capacitance and voltage ratings. Capacitance is measured in microfarads, which may be written as MFD, uF, or µF. A dual run capacitor powers two separate motors, so it shows two capacitance numbers.
The larger number, 40 µF, powers the compressor. The smaller number, 5 µF, powers the outdoor fan motor. Both numbers must match your old part exactly.
The voltage rating shows the maximum voltage the part can handle safely. A 440/370V rating means the capacitor can replace either a 370V or a 440V unit. Voltage can always be the same or higher, but never lower.
How to Read the Terminals on a Dual Run Capacitor
Dual run capacitors have three sets of terminals on top. Each terminal group connects to a specific motor circuit.
Taking a photo before disconnecting any wires helps you put everything back in the right place.
- HERM connects to the compressor motor.
- FAN connects to the outdoor fan motor.
- C stands for common and connects to the incoming power circuit.
Comparing Shapes and Listed Parts
Capacitors with identical electrical ratings do the same job regardless of shape. Round and oval shapes work the same way electrically. Choose the physical shape that fits your unit's mounting bracket securely.
The Bluefin CPDRR1-405 is a round dual run capacitor rated for 40+5 µF and 440/370V.
The Titan Pro TRCFD405 is a round dual run capacitor rated for 40+5 µF and 440/370V. It replaces part numbers CD40-5X440R, CAP-40/5/440R, and TRCD405.
The Titan Pro TOCFD405 is an oval dual run capacitor rated for 40+5 µF and 440/370V. It replaces part numbers CD40-5X440 and CAP-40/5/440.
Common Signs of a Failed Run Capacitor
When a run capacitor goes bad, the motors cannot get the push they need to operate. A common sign is an outdoor fan that hums loudly but will not spin. Homeowners often think the fan motor is broken when the capacitor is the real issue.
The compressor may also fail to start or may shut off quickly under load. Physical signs of failure on the capacitor body include bulging on the top terminal plate or leaking fluid from the can.
How to confirm it fits
- Shut off power at the breaker and the disconnect, discharge the terminals, and remove the old capacitor.
- Check the capacitance label to confirm it reads 40+5 µF, 40+5 MFD, or 40/5 uF. Both numbers must match.
- Check the voltage rating on the label. It must say 370V, 440V, or 440/370V. A 440V rating safely replaces 370V.
- Look at the physical shape of the old can. Check whether your mounting bracket holds a round or oval capacitor.
- Verify that the top of the can has three terminal posts labeled HERM, FAN, and C.
Questions
Can a 440V capacitor replace a 370V capacitor?
Yes. A 440V capacitor safely replaces a 370V capacitor. Voltage ratings can be the same or higher, but you must never use a lower voltage rating.
What is the difference between round and oval capacitors?
Round and oval capacitors with the same microfarad and voltage ratings perform the exact same electrical job. You only need to match the shape so it fits into the metal mounting bracket inside your equipment.
What happens if the microfarad rating does not match?
The capacitance rating must match the equipment requirements. Using the wrong microfarad rating can cause motors to run hot, hum, or fail to start.
How can I tell a dual run capacitor from a single run capacitor?
A dual run capacitor powers two motors and has three terminals marked HERM, FAN, and C. A single run capacitor powers only one motor and has two terminals.
Related guides
Brand names and part numbers are used only to show fit. HVAC Fitter is not affiliated with, authorized by, or endorsed by any equipment maker. If you are not sure a repair is safe for you, call a licensed HVAC technician.