The right UPS capacity begins with your load

How to choose the right UPS capacity

UPS selection starts with the equipment it must support. A rating alone does not tell you the available backup time, the required input supply or whether the installation fits your site. RAPSTECH supplies online, rack, tower, three-phase and modular UPS ranges. Use this checklist to prepare a useful sizing enquiry.

1. List the protected equipment

Record each device, quantity and actual operating power where available. Separate essential equipment from loads that can shut down during an outage. For servers and network equipment, distinguish measured demand from the maximum rating printed on a power supply. Include planned additions and any starting or transient loads that need review.

2. Check both kW and kVA

The selected UPS must accommodate the real power in kW and apparent power in kVA, within the manufacturer’s stated limits. Load power factor affects the relationship between them. Avoid selecting a model from a kVA number alone. Share equipment specifications or site measurements so the power requirement can be assessed.

3. Define what backup time must achieve

Do you need time for an orderly shutdown, a short interruption, or generator changeover? Battery runtime depends on the connected load, battery configuration, condition and operating environment. Request a runtime assessment for the proposed configuration; do not assume that two systems with the same kVA rating will run for the same duration.

4. Confirm the electrical supply and location

Provide input and output phase requirements, available supply details, installation location and cable-route constraints. Check access, ventilation, heat removal, floor or rack space and battery accommodation. Electrical protection, cabling and earthing should be reviewed by qualified personnel before installation.

5. Choose the format and growth approach

• Tower: consider available floor space and battery placement.
• Rack: review cabinet depth, rail compatibility, weight, ventilation and cable access.
• Three-phase: review supply arrangement, load distribution and installation requirements.
• Modular: review the actual expansion and redundancy options of the proposed system; the word modular alone does not establish redundancy.

What to send for a UPS sizing review

Send an equipment list, measured or documented load, desired backup duration, input/output phase, site location, existing UPS details and expansion plans. Include rack or room dimensions where relevant. RAPSTECH can discuss the suitable product range and the information needed for a proposal.

Frequently asked questions

Does a larger UPS always give longer backup?

No. Power capacity and battery energy are different considerations. Runtime must be reviewed for the connected load and battery configuration.

Can the same model suit every site?

No. Supply, load characteristics, environment and service access can change the selection. Confirm suitability for the specific application.

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