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A switch that stays lit while the router goes dark usually means the two were not on the same protected power path, or that the router failed or lost power for its own reason. A UPS (uninterruptible power supply) protects only the equipment plugged into its battery-backed outlets. A powered switch therefore proves very little about whether the router, the modem or fiber terminal, or the provider’s network stayed available.
This account is the author’s own report. No outage log, equipment inventory, UPS configuration, battery test record, or provider status history is available, so the exact cause at this depot is not established. What follows explains how to narrow it down, how to size a UPS for a network closet, and how to read runtime figures without assuming more than the manufacturer states.
What a UPS actually protects
Schneider Electric’s UPS buying guide defines the device this way: “A UPS (Uninterruptible Power Supply) is a battery backup system that provides instant emergency power during outages and protects connected devices from power spikes and failures.” The key phrase for a network closet is connected devices. The battery only helps the units plugged into outlets the UPS actually feeds from its battery.
Many UPS models have two kinds of outlets: battery-backed outlets and outlets that offer surge protection only. The labels are usually on the rear panel. If the switch was on a battery-backed outlet and the router was on a surge-only outlet, a wall outlet, or a separate power strip, the router would lose power while the switch kept running. Check the labels on the actual unit before assuming how the closet was wired.
#1 Best Overall
- 425VA/260W Standby Uninterruptible Power Supply (UPS): Uses simulated sine wave output to provide battery backup power and to safeguard home office, home entertainment including computers, gaming consoles, and broadband routers
- 8 NEMA 5-15R OUTLETS: Four battery backup & surge protected outlets; Four surge protected outlets; INPUT: NEMA 5-15P right angle, 45 degree offset plug with five foot power cord
- ADDITIONAL FEATURES: LED status light indicates Power-On and Wiring Fault, transformer-spaced outlets
- GREENPOWER UPS HIGH EFFICIENCY DESIGN: Reduces power consumption by utilizing a compact charger and power inverter to create an ultra-efficient backup power system for home and office use
- 3-YEAR WARRANTY – INCLUDING THE BATTERY; 75K USD Connected Equipment Guarantee; UL SAFETY CERTIFIED: Product has been tested in a UL certified lab and listed with UL as meeting or exceeding safety standards
Why the switch can stay on while the router does not
The table below lists the common explanations, the pattern each one produces, and what to check. These are hypotheses to test, not conclusions drawn from this incident.
| Observed pattern | What it suggests | What to check |
|---|---|---|
| Switch on, router off, router cord not plugged into a battery-backed outlet | The two devices were on different power paths | Trace the router’s power cord to its outlet. Compare that outlet’s label with the switch’s outlet on the UPS rear panel. |
| Both devices on the UPS, UPS shut down or alarmed during the outage | Overload or a depleted battery. Eaton cautions that exceeding UPS capacity can cause it to drop the load during an outage. | Read the load display and alarm history. Check the battery’s age and the result of its last self-test. |
| Router unpowered while the UPS was still running | The router lost power for its own reason, such as a failed power adapter or internal supply | Check the router’s power indicator and its adapter. Check the building breaker for the circuit that serves the closet. |
| Router powered, but no internet service | Local equipment stayed powered while the upstream network or provider did not | Check the modem or fiber terminal (ONT) status lights and the provider’s outage notices. |
Local power is not internet service
Internet access depends on a chain: the switch, the router, the modem or ONT, and the provider’s network beyond the building. A UPS can keep any link in that chain powered only if the link is connected to it. It cannot keep the provider’s network up. A UPS therefore cannot guarantee internet service during an outage, even when every device in the closet is protected. A lit switch should be read as evidence that one device had power, nothing more.
Rank #2
- 1500VA/1000W PFC Sinewave Uninterruptible Power Supply (UPS): Uses sine wave output to provide battery backup power for Active PFC & conventional power supplies; Safeguards computers, workstations, network devices, and telecom equipment
- 12 NEMA 5-15R OUTLETS: 6 battery backup & surge protected outlets, 6 surge protected outlets; INPUT: NEMA 5-15P right angle, 45 degree offset plug with 5 foot power cord; 2 USB charge ports (1 Type-A, 1 Type-C) quickly charge phones and tablets
- MULTIFUNCTION, COLOR LCD PANEL: Displays immediate, detailed information on battery and power conditions; Color display alerts users to potential issues before they can affect critical equipment and cause downtime; Screen tilts up to 22 degrees
- AUTOMATIC VOLTAGE REGULATION (AVR): Corrects minor power fluctuations without switching to battery power; UL SAFETY CERTIFIED: Product has been tested in a UL certified lab and listed with UL as meeting or exceeding safety standards
- 3-YEAR WARRANTY – INCLUDING THE BATTERY; $500,000 Connected Equipment Guarantee; FREE PowerPanel Management Software (Download)
How to size a UPS for a network closet
Eaton’s network and server UPS guidance recommends choosing a UPS whose watt capacity exceeds the connected load, and confirming compatibility before buying. Follow these steps:
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- Find each device’s power requirement. Use the manufacturer documentation or the nameplate. If the nameplate gives only amps, multiply amps by the AC voltage to estimate watts, as Eaton describes.
- Total the wattage. Use the sum of the devices, not a guess based on the switch alone.
- Compare watts with the UPS’s watt rating, not only its VA rating. VA and watts are not interchangeable selection figures. Keep the connected load within the manufacturer’s stated limit.
- Check the runtime chart at your real load. Do not infer runtime from VA alone. Runtime varies with load and with the specific UPS and battery.
- Check the outlets and electrical fit. Confirm that the required outlets are battery-backed, and that the plug type, voltage, and circuit suit the unit.
- If you need longer runtime, evaluate the options. These include a compatible external battery module, a generator plan, or load shedding. Load shedding means turning off nonessential equipment during an outage so critical devices last longer.
Reading a runtime figure
Eaton gives an illustrative example for a 2,200 VA UPS. Its scenario has ten nonessential devices and four essential devices, each drawing 100 watts. Eaton says runtime can rise from six minutes to more than half an hour by turning off the nonessential devices during an outage. The page reviewed does not show a publication date. Treat the figures as one manufacturer’s example, not a guarantee for any other setup.
Rank #3
- 1500VA / 900W RELIABLE BACKUP POWER: The highest VA capacity available for home use; delivers short-term battery power to keep essential devices powered during blackouts, surges, and unexpected power interruptions
- TEN PROTECTED OUTLETS: Power your entire setup with 5 battery backup outlets for essential devices, and 5 surge-only outlets for peripherals. Plus built-in coaxial and Ethernet surge protection for added peace of mind
- AUTOMATIC VOLTAGE REGULATION (AVR): Corrects low voltage brownouts (88V+) and surges (+/-13%) without draining battery. Boosts or trims to stable 120V. Extends runtime for blackouts; Active PFC compatible for gaming PCs
- REPLACEABLE BATTERY & ENERGY STAR UPS: User-replaceable battery (APCRBC124, sold separately) for zero-downtime swaps. ENERGY STAR certified for 92%+ efficiency, cutting energy costs vs standard UPS units
- LCD DISPLAY PANEL: Features an intuitive LCD screen that displays real-time status information including battery charge level, estimated runtime, load capacity, and input voltage for easy monitoring of your power protection system
Eaton’s guidance on load shedding puts the principle this way: “Load shedding allows you to prioritize the battery backup runtime of your critical equipment by automatically turning off nonessential equipment during longer outages.”
Choosing equipment for a closet
Schneider Electric’s guide separates basic home and office units from business and enterprise models. It notes that business models may offer network management and extended runtime options. When comparing units, check these items against the devices you have measured:
Rank #4
- 1500VA/900W Intelligent LCD Uninterruptible Power Supply (UPS): Uses simulated sine wave technology to provide battery backup power to safeguard workstations, networking devices, and home entertainment equipment
- 12 NEMA 5-15R OUTLETS: Six battery backup & surge protected outlets; six surge protected outlets; INPUT: NEMA 5-15P plug with 6-foot power cord; USB charge ports (1 Type-A, 1 Type-C) quickly charge mobile phones and tablets
- MULTIFUNCTION, COLOR LCD PANEL: Displays immediate, detailed information on battery and power conditions; Color display alerts users to potential issues before they can affect critical equipment and cause downtime
- AUTOMATIC VOLTAGE REGULATION (AVR): Corrects minor power fluctuations without switching to battery power; UL SAFETY CERTIFIED: Product has been tested in a UL certified lab and listed with UL as meeting or exceeding safety standards
- 3-YEAR WARRANTY – INCLUDING THE BATTERY; 500,000 Connected Equipment Guarantee; FREE PowerPanel Personal Software (Download)
- Total measured watt load and watt headroom above it
- Runtime at the expected load, taken from the manufacturer’s chart
- Battery age, and whether the battery can be replaced
- Number and type of battery-backed outlets
- Plug, voltage, and circuit compatibility
- Rack or desktop form factor
- Waveform requirements for the connected equipment
- Remote monitoring and support for external batteries or load management
Eaton adds that network and server UPS selection should account for mission-critical use, load, rack installation, pure sine-wave needs, remote management, and extended-runtime needs.
A listed example: the Eaton-cited SMART1500SLT
Eaton lists the Tripp Lite SmartPro SMART1500SLT as a line-interactive UPS suitable for network devices. The manufacturer’s product page reports the following. These are manufacturer-listed specifications, not a recommendation for any particular closet. Confirm them on the current product page before buying.
Best Value
- 12 NEMA 5-15R OUTLETS: Six battery backup & surge protected outlets; Six surge protected outlets (Three ECO controlled); INPUT: NEMA 5-15P right angle, 45 degree offset plug with five foot power cord
- MULTIFUNCTION LCD PANEL: Displays immediate, detailed information on battery and power conditions
- ECO MODE: When the UPS detects a computer is off or in sleep mode, it will automatically turn off power to computer peripherals connected to ECO mode outlets, reducing power usage and lowering energy costs
- 3-YEAR WARRANTY – INCLUDING THE BATTERY; $100,000 Connected Equipment Guarantee and FREE PowerPanel Personal Edition Management Software (Download)
| Specification | Manufacturer-listed value |
|---|---|
| Output capacity | 900 W |
| Runtime at full load (900 W) | 8 minutes |
| Runtime at half load | 20 minutes |
| Replacement battery | RBC36-SLT |
The listed runtimes apply only at the stated loads. A closet with a different total draw, an older battery, or a different installation will not reproduce them.
Quick Recap
If the router goes dark during the next outage
- Check which outlet the router is plugged into. If it is not a battery-backed outlet, move it to one, and confirm the label on the UPS.
- Read the UPS display or indicator lights for an overload, a battery fault, or a shutdown alarm.
- Check the battery age and run the unit’s self-test if it has one. Replace the battery if it is old or fails the test.
- Check the router’s own power indicator and its adapter. If the router is powered but offline, check the modem or ONT status lights.
- Check the provider’s outage notices. If the upstream network is down, no local change will restore service.
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