Avoid UPS Overload: 5 Things You Should Never Plug Into a UPS

A UPS protects your critical equipment, but only when used correctly. Here are five things you should never plug into a UPS if you want to avoid UPS overload.

What is UPS Overload?

A UPS overload happens when the total power draw of everything connected to the unit exceeds its rated capacity. Every UPS is built to handle a specific amount of load, measured in watts (and sometimes VA, or volt-amps) — and when the equipment plugged into it asks for more power than that, the UPS can't safely deliver it.

When this happens, most UPS units will respond in one of a few ways: sound an audible alarm, display an overload warning, switch to bypass mode (which removes battery protection entirely), or shut down outright to protect itself from damage. In any of these cases, the equipment that was supposed to be protected is now running unprotected — which defeats the purpose of having a UPS in the first place.

What Causes a UPS to Overload?

UPS overloads typically come down to one of a few root causes:

• Too much equipment connected. Over time, it's common for additional devices to get added to a UPS without anyone recalculating the total load. What started as a reasonably loaded unit slowly creeps towards or past its limit.

• High-draw devices plugged in. Certain equipment (laser printers, space heaters, devices with motors) pulls dramatically more power than their steady-state rating suggests, especially during startup. A device that seems minor on paper can spike well past what the UPS can absorb.

• Confusing VA and watts. UPS units are often rated in both VA and watts, and the two numbers aren't the same. Sizing a load based on VA alone can make a UPS look like it has more headroom than it actually does, leading to accidental overloads.

• Daisy-chained or add-on equipment. Connecting a second UPS, an unaccounted-for power strip, or additional PDUs downstream can quietly add load that isn't factored into the original capacity planning.

• Aging or under-sized battery/UPS setups. As a facility grows, the equipment load often grows with it, but the UPS doesn't always get resized to match. A unit that was correctly sized five years ago may be undersized for today's setup.

5 Things to Never Plug Into a UPS

1. Laser Printers

Laser printers draw a massive power spike every time the fuser activates, often 3 to 10 times their rated wattage. That's enough to trigger an overload, drain the battery, or trip the internal breaker.

Bottom line: Plug your laser printer into a wall outlet or surge protector. If the power goes out mid-print, no data is lost. Your servers and workstations are what need protecting.

2. Space Heaters and High-Wattage Appliances

Heaters, coffeemakers, mini-fridges, and similar devices draw far more continuous power than a UPS is built to handle. They can cause the unit to overheat, trigger alarms, or permanently damage internal components.

Bottom line: If it generates heat or has a motor, it doesn't belong on a UPS. Reserve those outlets for IT equipment and network gear.

3. Another UPS (Daisy Chaining)

Connecting one UPS to the output of another seems like a way to extend runtime, but it actually increases failure risk for both units and can cause the upstream UPS to cycle constantly between battery and normal operation.

Bottom line: If you need more runtime, look for a model that supports extended battery modules. If you need redundancy, use isolated dual UPS systems, not daisy chains. If you need more outlets, consider adding a PDU to your set up.

4. A Surge Protector

A quality UPS already has surge protection built in. Stacking a surge protector on top of it can cause the two devices to interfere with each other and reduce protection quality.

Bottom line: If you need more outlets, use a basic power strip with no surge protection and stay within your UPS's rated watt capacity.

5. More Equipment Than the UPS Can Handle

Every UPS has a rated watt capacity. Exceed it and the UPS will alarm, switch to bypass, or shut down, leaving your equipment completely unprotected.

Bottom line: Add up the wattage of everything connected to your UPS and stay at 80% of the rated capacity or below. Note that VA ratings can be misleading, always check the watt rating as that's the true power capacity of the UPS.

Not Sure If Your UPS Setup Is Right to Avoid UPS Overload?

If your facility's UPS configuration has grown over the years without a formal review, it's worth having a technician take a look. ORE Power can assess your connected load and make sure you're protected the right way.

📞 24/7 Emergency Line: 888-709-2338 📧 Non-urgent: Request a quote online

Related reading:

• UPS Beeping? Here's What Each Alarm Means

• What to Do When Your UPS Is in Alarm