APC UPS AVR Trimming Alert — What It Means

What Does This Error Mean?

AVR Trimming means the input mains voltage is too high and the UPS Automatic Voltage Regulation circuit is reducing (trimming) it before passing it to the connected equipment. This is a normal function of the UPS and does not require action if it occurs occasionally. Frequent or constant trimming suggests the mains voltage in your location is running consistently high.

Affected Models

APC Smart-UPS SMT series
APC Smart-UPS SMX series
APC Back-UPS Pro with AVR
APC Easy-UPS with AVR

Common Causes

Mains grid voltage running above the nominal range — common in some areas and at off-peak hours
Long cable runs from the distribution board to the UPS causing voltage rise
Heavy electrical equipment (motors, air conditioners) switching off and briefly raising voltage
Neutral conductor issue in building wiring causing one phase to rise

How to Fix It

Check how often the trimming occurs.

Brief, occasional AVR Trimming — especially in the evenings when industrial loads switch off — is normal. Log events in APC PowerChute Personal Edition: Settings → Events. If it appears only a few times a week, no action is needed.
Check the incoming voltage with a multimeter.

Measure the voltage at the wall outlet the UPS is plugged into. Most UPS units for 230V countries have an upper trim threshold of 253–260V. If the reading is consistently above this, your grid voltage is high.
Report persistent high voltage to your electricity provider.

In most countries the regulated supply voltage must stay within ±10% of nominal. If your measured voltage is consistently above this, your electricity provider is obligated to investigate and correct it.
Move the UPS to a circuit closer to the distribution board.

Long wiring runs can cause a small voltage rise at the outlet end. If possible, use a shorter power run from the distribution board to reduce this effect.

When to Call a Professional

If AVR Trimming occurs constantly (not just briefly) and is accompanied by the UPS running warm, have a licensed electrician measure the incoming voltage at the distribution board to confirm a wiring issue is not responsible.

Frequently Asked Questions

Does AVR Trimming use battery power?

No. AVR Trimming is a transformer-based function in the UPS and does not use the battery at all. The battery is only used when mains power fails completely.

What is the difference between AVR Trimming and AVR Boosting?

AVR Trimming reduces voltage that is too high. AVR Boosting raises voltage that is too low. Both are normal UPS functions that protect equipment from voltage fluctuations without switching to battery.