Numeric UPS (by Legrand) — VA Rating Sizing Guide + Hyderabad Dealer Guide

Quick Answer

To size a Numeric (Legrand) UPS correctly: add up the running wattage of everything you want protected, divide by an assumed power-factor of 0.7–0.8 for mixed electronic loads to get VA, then apply a 20–25% headroom margin for inrush current and future growth. The resulting VA figure — not the wattage figure — is what you match against a UPS model’s rated VA. Backup runtime is a separate calculation driven by battery voltage and Ah, not by the UPS’s VA rating alone.

Step 1 — Add Up Your Connected Load

List every device that must stay powered and note its running wattage (from the nameplate or datasheet, not a guess):

Example load	Typical running wattage
Desktop PC + monitor	150–300 W
Wi-Fi router / modem	10–20 W
Small office (a few PCs + lights)	500–1,000 W
Home essentials (fans, lights, TV, router)	300–600 W
Server / small rack	500 W+ (check nameplate)

Add every device you actually want on backup power — don’t size for the whole building unless that is genuinely the intent.

Step 2 — Convert Watts to VA Using Power Factor

UPS units are rated in VA (apparent power), but your devices are usually labelled in watts (real power). The two are related by power factor (PF):

VA = Watts ÷ Power Factor

• Modern electronics (LED-lit laptops, most modern PSUs) run around PF 0.9–1.0.
• Mixed office/computer loads with older switch-mode supplies commonly run PF 0.7–0.8 — use 0.7–0.8 if you are not certain, as it is the more conservative (safer) assumption and avoids undersizing.

Worked example — small office: A small office draws 800 W of connected load at an assumed PF of 0.7. VA required = 800 ÷ 0.7 = 1,143 VA

Step 3 — Add Headroom for Inrush and Growth

Add roughly 20–25% margin on top of the calculated VA to account for the inrush current devices draw at power-on (motors, PSUs, monitors) and for any load you expect to add later. Continuing the small-office example:

1,143 VA × 1.25 = ~1,430 VA → round up to the next standard UPS rating.

Worked Sizing Examples

The single-load table above is a starting point; real sizing decisions are made per-room and per-application. Three worked examples below cover the load profiles eNarayan customers most commonly ask about — a small clinic, a retail store, and a server room. Each follows the same four-step method: list load → convert to VA → add headroom → round up to a model.

Example A — Small Clinic / Diagnostic Room

A typical small clinic wants backup for diagnostic and reception equipment during a power cut, not the whole premises (air conditioning and general lighting are usually excluded from UPS backup and left on a DG or grid-only circuit).

Equipment	Running wattage
Diagnostic equipment (ECG/small analyser, load-dependent)	150–300 W
Reception PC + monitor + billing printer	250–350 W
Networking (router, switch, Wi-Fi AP)	30–50 W
Emergency/task lighting (LED)	40–80 W
Total connected load	~470–780 W

Taking the higher end (780 W) at PF 0.7: VA required = 780 ÷ 0.7 = 1,114 VA. Add 25% headroom: 1,114 × 1.25 ≈ 1,393 VA, rounding up to a 2,000 VA class UPS for margin, or a 1,000–1,500 VA unit if the clinic is comfortable sizing tighter to the lower end of the load range. Because clinical settings often value the cleaner output and zero transfer time of online double-conversion technology for sensitive diagnostic electronics, an entry single-phase online model is worth discussing even at this load size, not just a line-interactive residential unit — this is a specification decision, not a wattage one, and should be confirmed with the dealer against the specific diagnostic equipment’s sensitivity requirements.

Example B — Retail Store (POS + Lighting + Security)

Equipment	Running wattage
POS terminal + billing printer + barcode scanner	150–250 W
Networking equipment	30–50 W
CCTV/DVR + monitor	80–150 W
Display/task lighting on backup (partial, LED)	100–200 W
Total connected load	~360–650 W

Taking 650 W at PF 0.7: VA required = 650 ÷ 0.7 = 929 VA. Add 25%: 929 × 1.25 ≈ 1,161 VA, rounding up to a 1,500–2,000 VA residential/plug-and-play class model. A retail store’s main sizing risk is under-scoping “which lights count” — confirm with the store owner exactly which circuits are expected to stay lit during a cut before finalising the wattage list, since that is the single biggest swing factor in this example.

Example C — Small Server Room / Server Rack

Equipment	Running wattage
1U/2U server(s), typical small rack	500–800 W (check nameplate per unit — this varies widely)
Network switch/router/firewall	50–100 W
Rack-mount monitor/KVM (if present)	30–50 W
Total connected load	~580–950 W

Taking the higher figure (950 W) at PF 0.8 (server PSUs typically run a better power factor than mixed office loads, but confirm from the nameplate rather than assuming): VA required = 950 ÷ 0.8 = 1,188 VA. Add 25% headroom for inrush and near-term growth: 1,188 × 1.25 ≈ 1,485 VA. For a server room, the recommendation shifts from “round up to the nearest residential model” to “specify an online double-conversion unit” almost by default — server hardware is exactly the sensitive-load category double-conversion technology is designed to protect, and even a small server room commonly moves to the single-phase online tier (Valura or entry Onfiniti⁺) rather than a line-interactive Digital-series unit, specifically for the zero-transfer-time and cleaner output characteristics described in the Line-Interactive vs Online section below.

A note on all three examples: these are illustrative wattage ranges to demonstrate the sizing method, not a substitute for reading actual nameplate wattage off the specific equipment being protected. Real installed loads vary by brand/model of the equipment in question — always total the real nameplate figures for the actual site before finalising an order.

Step 4 — Match to a Numeric UPS Model

Numeric (Legrand) sells across residential/plug-and-play, single-phase online, and three-phase/modular tiers. Match your calculated VA requirement — do not buy the nearest model down; round up.

Residential / Plug-and-Play (line-interactive):

• Digital 600 EX — 600 VA
• Digital 1000 PLUS V — 1,000 VA
• Digital 1000 HR-V IBB — 1,000 VA
• Digital 2000 Plus — 2,000 VA
• Digital 2000 HR-V IBB — 2,000 VA
• Keor SP (line-interactive) — spans a 600–2,000 VA range across its variants

Single-Phase Online (higher-reliability double-conversion, small office / server):

• Valura / Valura IBB — 1–3 kVA (1, 2 and 3 kVA variants; IBB variants carry inbuilt batteries)
• Onfiniti⁺ — 1–10 kVA (1, 2, 3, 6 and 10 kVA variants)
• Premius Edge / Premius Edge Rack — 1–10 kVA
• Premius RT — 7.5–20 kVA (7.5, 10, 15 and 20 kVA variants)

Three-Phase / Modular (larger commercial and industrial installations):

• HPi 33 EVO — 10–40 kW
• Keor T EVO — 15–60 kVA
• Keor MP — 60–200 kW
• Keor HPE — 60–600 kW
• Trimod HE (modular) — 10–80 kW
• Keor MOD / Keor MOD+ (modular) — up to 1,800 kW at the top of the range

For the small-office worked example above (~1,430 VA target), a Digital 2000 Plus (2,000 VA) or, for higher reliability on a small office/server load, an entry-tier Onfiniti⁺ would both clear the requirement with headroom.

Exact current-model availability and pricing should always be confirmed against eNarayan Elex’s live stock at the time of order — the model list above reflects the published Numeric UPS product range and is not a live stock feed.

Step 5 — Backup Time Is a Separate Question From VA Rating

VA rating tells you the maximum load the UPS can carry — it does not tell you how long the battery lasts. Backup runtime depends on:

Runtime (hours) ≈ (Battery Voltage × Battery Ah × Efficiency) ÷ Load in Watts

A higher-VA UPS running a light load will hold backup far longer than the same UPS near its rated capacity. If your priority is runtime (e.g., a 2–3 hour power cut is common in your area), size the battery bank Ah for that target runtime at your actual load wattage — this is a conversation to have with the dealer at order time, since Ah/battery-bank sizing is project-specific and not printed on a standard sizing chart.

How Battery Configuration Changes the Runtime Answer

Three practical levers change the runtime a given UPS delivers, and it’s worth understanding all three before assuming “bigger VA = longer backup”:

1. Load vs rated capacity. Running a UPS at 30% of its rated VA gives materially longer backup than running it near 90% of rated VA — even though both scenarios use “the same UPS.” This is why the worked examples above intentionally add headroom: a UPS with margin above the actual load also runs cooler and holds backup longer at the real (lower) load, not just for safety against inrush spikes.
2. Internal vs external battery. Standard/IBB (inbuilt-battery) models carry a fixed internal battery sized for a baseline runtime — commonly in the tens-of-minutes range at full load, longer at partial load. External-battery (EBM/extended-battery module) variants let the battery bank be sized independently of the UPS’s power rating, which is the correct approach whenever the requirement is measured in hours rather than minutes.
3. Battery age and depth of discharge. A battery bank’s usable runtime degrades over its service life and is affected by how deeply it’s discharged on each cycle — this is a maintenance/replacement planning topic, not a one-time sizing topic, and worth raising with the dealer as an ongoing consideration rather than a single order-time decision.

Line-Interactive vs Online (Double-Conversion) — Which One Do You Need?

This is the single most consequential specification decision after VA sizing, and it’s frequently skipped in favour of just picking a VA number. The two technologies solve different problems.

Factor	Line-Interactive (Digital / Keor SP series)	Online / Double-Conversion (Valura, Onfiniti⁺, Premius, Keor ranges)
How it works	Regulates incoming voltage (AVR) and stays on mains most of the time; switches to battery/inverter only on an actual outage	Continuously converts incoming AC to DC then back to AC through the inverter — the load is never directly on raw mains
Transfer time on outage	Small but non-zero transfer time as it switches to battery	Zero transfer time — the inverter is already powering the load, so there’s no switchover gap
Output waveform/quality	Generally good, but not continuously conditioned the way online output is	Continuously conditioned, clean sine-wave output regardless of incoming mains quality
Best suited for	Home use, general office PCs, retail POS — loads that tolerate a brief transfer and don’t need continuous conditioning	Servers, medical/diagnostic equipment, networking core equipment, and any load sensitive to even momentary transfer gaps or dirty incoming power
Typical Numeric product line	Digital series, Keor SP	Valura, Onfiniti⁺, Premius Edge/RT, and the three-phase Keor range
Relative cost	Lower cost per VA	Higher cost per VA, justified by the reliability/output-quality improvement for sensitive loads

Rule of thumb: if the load is a server, a piece of diagnostic/medical electronics, a networking core switch, or anything where even a fraction-of-a-second interruption is unacceptable, specify online/double-conversion regardless of how small the VA requirement is. If the load is general office or home equipment that tolerates a brief transfer, line-interactive is the cost-appropriate choice.

Buying Numeric UPS in Hyderabad — eNarayan Elex, Rasoolpura

eNarayan Elex stocks the Numeric (by Legrand) UPS range from Rasoolpura, Hyderabad (GST 36AACCE0195K1ZK) and supplies across Telangana and Andhra Pradesh for both residential and commercial/industrial orders. For a sizing recommendation specific to your load, share:

1. The list of devices/equipment to be backed up, with running wattage
2. Whether the requirement is residential (plug-and-play), a small office/server (online single-phase), or a larger commercial/industrial installation (three-phase/modular)
3. The target backup runtime in minutes/hours
4. Whether any of the load is sensitive/critical (servers, diagnostics) — this determines line-interactive vs online, not just the VA number

…and the correct VA rating and model can be confirmed against current stock — send an enquiry and eNarayan Elex’s technical sales team will size it with you.

Already sorted on UPS sizing? eNarayan Elex also supplies the switchgear (MCB/MCCB/RCCB/ACB) that protects the same circuits — see our switchgear buyer’s guide.

Frequently Asked Questions