36-20R3744 Rotom Run Capacitor for HVAC Motors, Restores Reliable Motor Starting and Operation

Rotom 36-20R3744 is a round single-value motor-run capacitor rated 20 MFD at 370/440 VAC. It supersedes earlier Rotom reference 20ER; the matching U.S. part number is 20DVR.

The capacitor helps maintain the correct phase shift and operating torque for compatible HVAC fan, blower, pump and other permanent-split-capacitor motors.

A weak, swollen, leaking or open capacitor may contribute to a motor that hums, starts slowly, overheats, runs intermittently or fails to reach normal speed.

Match the original capacitance exactly at 20 MFD. A 440V or 370/440V capacitor may replace a 370V unit, but a 370V-only capacitor must not replace a 440V unit. Confirm the case shape, diameter (1.78 in / 45 mm), height (3.15 in / 80 mm), terminal arrangement and available mounting space before ordering.

Capacitors can retain an electrical charge after power is disconnected. Service should be performed by a qualified HVAC technician following approved electrical-safety procedures.

Is This the Right Part?

Suitable for motors requiring a 20 MFD run capacitor with an equal or lower voltage requirement and compatible physical dimensions. The replacement must be a motor-run capacitor with exactly 20 MFD capacitance, an equal or higher voltage rating and compatible terminals and dimensions.

Common Symptoms

• Motor hums but does not start or starts very slowly
• Motor overheats during normal operation
• Motor runs intermittently or shuts off unexpectedly
• Fan or blower fails to reach normal operating speed
• Capacitor case is visibly swollen, bulging or leaking

Check Before Replacing

• Test the capacitor with a capacitance meter — compare the reading against the tolerance printed on the original label. A reading outside tolerance confirms failure; a reading within tolerance suggests another cause.
• Confirm the original is a single-value 20 MFD motor-run capacitor — do not substitute a 20/5 MFD dual-run capacitor without intentional rewiring of both sections.
• Verify the original voltage rating — a 440V or 370/440V replacement is acceptable for a 370V application; a 370V-only capacitor must not replace a 440V-rated application.
• Confirm the round case dimensions (1.78 in diameter × 3.15 in height) and terminal arrangement fit the available mounting space before ordering.

Part Details

Installation Notes

1. Disconnect and lock out power to the HVAC equipment before servicing.
2. Safely discharge the original capacitor before touching any terminals — capacitors retain charge after power is removed.
3. Photograph the original wiring and terminal connections before disconnecting.
4. Compare the new capacitor with the original — confirm capacitance, voltage, case shape, diameter, height and terminal type.
5. Inspect nearby wiring, connectors and motor windings for damage while the capacitor is removed.
6. After installation, restore power and test the motor for correct starting and running behaviour.

Use a qualified HVAC or electrical technician when diagnosis or installation is outside your experience.

Verified Compatible Applications

This capacitor is selected by electrical and dimensional specifications, not by appliance or equipment model number. It is suitable for compatible applications requiring a single-section 20 MFD round run capacitor rated 370V or 440V.

Fitment reminder: Match capacitance (exactly 20 MFD), voltage (370V or 440V), capacitor type (single-section motor run), case shape (round), terminal configuration and available mounting space before ordering.