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Error code reference

Mitsubishi Air Conditioner Error Code E.OV2

Regenerative overvoltage trip during constant speed

Mitsubishi codesMitsubishi air conditioner codes

Regenerative overvoltage trip during constant speed - internal main circuit DC voltage exceeded specified value.

First step from the service manual

Check for sudden load change and Pr.22 Stall prevention operation level setting.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What E.OV2 means on a Mitsubishi air conditioner

The E.OV2 error code on a Mitsubishi air conditioner indicates a regenerative overvoltage trip that occurs specifically during constant-speed operation. This means the internal main circuit DC bus voltage has risen above the system's specified threshold while the compressor or motor is running at a steady speed. The inverter drive monitors this DC bus voltage continuously, and when regenerative energy causes it to spike beyond acceptable limits, the system trips to protect the power electronics from damage.

Regenerative overvoltage during constant speed is typically caused by sudden changes in mechanical load that force the motor to act as a generator, pushing voltage back into the DC bus. Unlike overvoltage faults that occur during deceleration, this fault points to dynamic load disturbances rather than improper deceleration settings. A key diagnostic area is the Pr.22 stall prevention operation level parameter, which controls how aggressively the drive responds to overcurrent conditions. If Pr.22 is set too low, the drive may react to normal load fluctuations in a way that contributes to voltage instability on the DC bus.

Additionally, sudden load changes on the refrigerant circuit, such as rapid pressure shifts caused by a failing expansion valve, refrigerant overcharge, or compressor issues, can create abrupt torque spikes that generate regenerative energy. Power supply irregularities, including voltage surges from the utility, can compound the problem by adding energy to an already-elevated DC bus. Addressing this fault requires reviewing both the drive parameter settings and the physical operating conditions of the refrigerant system.

Source: manufacturer service documentation.

Common causes of E.OV2

  1. 01

    Sudden mechanical load change

    Wiring / connection

    A rapid shift in compressor load, caused by refrigerant pressure swings or a mechanical issue, can push energy back into the DC bus and trigger the overvoltage trip. Check system pressures and monitor for irregular compressor behavior during operation.

  2. 02

    Pr.22 stall prevention level set incorrectly

    Wiring / connection

    If the Pr.22 parameter is configured at too low a value, the drive may respond to normal load variations in a way that destabilizes DC bus voltage. Review and adjust this parameter according to the system's specifications.

  3. 03

    Refrigerant overcharge or undercharge

    Wiring / connection

    Incorrect refrigerant charge creates abnormal pressure conditions that produce sudden torque loads on the compressor, which can trigger regenerative voltage spikes. Verify refrigerant charge levels with manifold gauges.

  4. 04

    Utility voltage surge or supply instability

    Wiring / connection

    Incoming voltage surges from the power supply add energy to the DC bus, raising it above the safe threshold when combined with normal operation. Check supply voltage for instability or transient spikes at the unit's power input.

  5. 05

    Failing expansion valve or refrigerant flow component

    Part replacement

    A malfunctioning expansion valve can cause erratic refrigerant flow and sudden pressure changes, leading to sharp compressor load spikes. Replacement of the valve may be required if refrigerant pressures are erratic.

See the test procedure for each cause

Frequently asked questions about E.OV2

What does E.OV2 mean on a Mitsubishi air_conditioner?
E.OV2 indicates a regenerative overvoltage trip that occurred while the unit was operating at constant speed. The internal main circuit DC bus voltage exceeded the allowable limit, causing the system to shut down as a protective measure. This is different from an overvoltage fault during deceleration and points specifically to sudden load changes or drive parameter issues.
How do I fix the E.OV2 error on my Mitsubishi air conditioner?
Start by checking for sudden load changes in the refrigerant system, including abnormal pressures caused by refrigerant charge issues or a failing expansion valve. Then review the Pr.22 stall prevention operation level parameter in the drive settings and adjust it if it is set too low. Also inspect the incoming power supply for voltage instability or surges. If the fault persists after addressing these factors, a qualified technician should inspect the inverter board and compressor.
Is the E.OV2 error dangerous to ignore?
Yes, continuing to operate a unit with a recurring E.OV2 fault can lead to damage to the inverter drive's power electronics, including the DC bus capacitors and transistor modules. The system shuts down specifically to prevent this kind of damage. Repeated faults without diagnosis and correction can result in costly component failures.
Will resetting the unit clear the E.OV2 error?
A power reset may clear the fault temporarily and allow the unit to restart, but if the underlying cause is not corrected, the error will return. Resetting alone is not a repair. The fault will continue to occur until the load conditions, parameter settings, or faulty components responsible for the DC bus overvoltage are addressed.
How much does it cost to repair an E.OV2 fault on a Mitsubishi air conditioner?
Repair costs vary significantly depending on the root cause. A parameter adjustment or refrigerant recharge may cost relatively little, typically in the range of $75 to $200 for a service visit. If an expansion valve, inverter board, or compressor requires replacement, costs can range from $300 to over $1,500 depending on the component and labor involved.

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