N10-009 Question 185
Single answerPower: Uninterruptible power supply (UPS), Power distribution unit (PDU), Power load, VoltageA network administrator is adding two new PoE access switches to a small server room. The rack already contains a firewall, router, and several existing switches connected to a rack-mounted UPS and PDU. Shortly after the new switches are installed, the UPS begins reporting overload alarms during peak business hours, even though utility power is stable. The administrator needs to keep critical network devices protected by battery backup and avoid unexpected shutdowns. Which action is the BEST next step?
- A
Move some noncritical equipment off the UPS-backed PDU to a non-UPS power source after verifying the total UPS load and runtime requirements
- B
Increase the voltage supplied by the wall outlet so the UPS can provide more wattage to the rack
- C
Replace the PDU with another basic PDU because the overload alarm indicates the PDU has failed
- D
Disable the UPS alarm because the devices are functioning normally and the building power is stable
Show answer and explanation
Correct answer: A
Explanation
This scenario tests practical understanding of the relationship between a UPS, a PDU, power load, and voltage. A PDU primarily distributes electrical power to multiple rack devices, while the UPS provides conditioned power and battery backup for connected loads. When new switches are added, especially PoE switches that can draw significantly more power under client load, the total wattage or VA demand may exceed the UPS rating. The best practice is to perform a load assessment using the UPS nameplate/rated capacity and the actual device power requirements, then prioritize critical devices for battery-backed circuits. Vendor documentation from UPS manufacturers commonly recommends keeping UPS load below maximum capacity to maintain reasonable runtime and avoid overload conditions. In real environments, noncritical devices may be moved to utility-only power or the UPS may need to be upgraded if all connected equipment must remain protected.
- A. Correct.
Correct. A UPS overload alarm typically indicates the connected equipment is drawing more power than the UPS is rated to support, not that utility power is unstable. The best immediate action is to calculate the actual power load, identify which devices truly require battery backup, and move noncritical devices to non-UPS power if appropriate. This preserves protected runtime for critical network infrastructure and aligns with common power-planning best practices.
- B. Incorrect.
Incorrect. Administrators cannot simply 'increase the voltage' from a wall outlet to make a UPS support more load. Power capacity is determined by the electrical circuit, the UPS design, and the equipment ratings. Changing supply voltage without proper electrical design would be unsafe and is not a normal operational fix. This option reflects a misconception that voltage can be arbitrarily raised to solve a load problem.
- C. Incorrect.
Incorrect. A PDU distributes power to devices, but an overload alarm from the UPS usually means the UPS itself is over capacity due to total connected load. Replacing a basic PDU with another basic PDU would not reduce the wattage draw of the connected equipment or increase available battery capacity. Someone might choose this if they confuse power distribution with power protection.
- D. Incorrect.
Incorrect. Disabling the alarm does not address the underlying overload condition. Even if utility power is currently stable, an overloaded UPS may fail to provide sufficient backup runtime or may shut down under battery conditions. Ignoring the alarm increases the risk of an outage during a power event.