CompTIA Server+ (SK0-005)Server Hardware Installation and ManagementMedium
A technician is sizing a UPS for a rack containing three identical servers, each drawing 400W under normal load. The UPS operates the connected load at a power factor of 0.9. Which of the following standard UPS VA ratings should the technician select to safely support this load?
- A1000VA
- B1500VA
- C2000VA
- D1200VA
Show answer & explanationAnswer & explanation
Correct answer: B. 1500VA
Total wattage is 3 x 400W = 1200W. VA = Watts / Power Factor = 1200 / 0.9 = 1333.3VA. The smallest standard UPS rating that exceeds this requirement is 1500VA; a 1200VA unit would be undersized.
Why the other options are wrong
- A. Far below the calculated requirement of about 1333VA.
- C. Oversized; unnecessarily exceeds the requirement and increases cost.
- D. Equal to the wattage but below the required VA after dividing by the power factor.
UPS VA Sizing
UPS capacity is rated in VA (volt-amps); actual wattage divided by the power factor gives the required VA rating needed to support a load.
- VA = Watts / Power Factor
- Power factor for IT loads is often around 0.9
- Always round up to the next standard UPS VA rating
Memory trick: Divide watts by the power factor to reveal the true VA giant hiding underneath.