UPS usage best practices: Which device should not be plugged into a standard uninterruptible power supply (UPS)?

Introduction / Context:
Uninterruptible power supplies provide battery-backed power and filtering for critical electronics. However, certain peripherals draw large inrush and sustained currents that can overload or rapidly deplete a standard UPS, compromising protection for truly critical devices.

Given Data / Assumptions:

• Typical office UPS units are sized for PCs, monitors, networking gear, and external modems.
• Laser printers have fusers that heat up and draw high peak currents.
• The question refers to a standard (not high-capacity) UPS.

Concept / Approach:
Laser printers' fuser assemblies consume significant power and can cause UPS overloads, voltage dips, or frequent battery drain. Best practice is to plug laser printers directly into a surge protector (not the battery-backed outlets) unless a UPS is explicitly rated for such loads. Monitors, modems, and ink-jet printers typically fall within UPS capacity and do not cause large inrush spikes like a fuser does.

Step-by-Step Solution:

Verification / Alternative check:
UPS vendor manuals warn against connecting laser printers to battery-backed outlets. Nameplate ratings for fusers confirm high VA draw compared to PCs or monitors.

Why Other Options Are Wrong:
Monitor, ink-jet printer, and external modem normally operate within UPS limits and benefit from backup and filtering.

Common Pitfalls:
Plugging a laser printer into battery-backed outlets causes nuisance trips and reduces runtime for critical equipment.

Final Answer:
laser printer