Electrical Load Calculator

Electrical Load Calculator

Gross Built-Up Floor Area (sq.m):

Covered Parking / Basement Area (sq.m):

Estimated Air Conditioning Capacity (Tons):

Number of Passenger Lifts (15kW each):

Substation Demand Diversity Factor: 50% Diversity (Standard Residential) 70% Diversity (Mixed Occupancy) 80% Diversity (Standard Office) 100% Diversity (Industrial / Continuous Load)

Load Analysis Results

Total Connected Load

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Calculated Maximum Demand

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Note:

• Lighting & Fan Loads: Calculated at 13 W/sq.m of all built-up floors.
• General Power Sockets: Sized at 55 W/sq.m for general-use power requirements.
• Basement/Parking: Calculated at a reduced energy envelope of 3.23 W/sq.m.
• HVAC Power Draw: Calculated at 1.25 kW/TR (incorporating both high-side chillers and low-side condenser pumps/AHUs).
• Lifts: Standard municipal traction passenger lifts are rated at 15 kW per lift.

⚡ Substation & Load Sizing Calculator

Perform advanced electrical load schedule calculations with APFC power factor correction, Single & N+1 transformer sizing, and dual DG backup sizing.

3-Phase System Voltage (V):

Uncorrected Raw PF:

Target APFC Corrected PF: 0.95 Lagging (Standard) 0.98 Lagging (Optimal Efficiency) 0.99 Lagging (Maximum Power Factor) No APFC (Uncorrected 0.88 PF)

Expansion Margin (%):

Area / Location	Equipment Description	Load Category	Qty	Watts (W)	Diversity %	Connected Load (kW)	Demand Load (kW)	Act
		General Utility Emergency Life-Safety				5.40	4.86
		General Utility Emergency Life-Safety				20.00	13.00
		General Utility Emergency Life-Safety				45.00	45.00
		General Utility Emergency Life-Safety				15.00	15.00

📊 Sizing Results & Infrastructure Recommendations

TOTAL CONNECTED LOAD

85.40 kW

97.05 kVA

MAX DEMAND LOAD (APFC 0.95 PF)

77.86 kW

81.96 kVA Corrected

REQUIRED APFC PANEL RATING

35 kVAR

Power Factor Correction (0.88 → 0.95)

1. SINGLE TRANSFORMER SIZING (1 x TF)

160 kVA

Single Unit (Loading: 58.9%)

2. N+1 REDUNDANT SCHEME (2 x TF)

2 x 160 kVA

N+1 Redundant Scheme (Loading: 29.5%)

OPERATIONAL BACKUP DG SET

125 kVA

Full Building Facility Backup

EMERGENCY BACKUP DG SET

62.5 kVA

Emergency Facility Backup

MAIN INCOMER BREAKER & BUSBAR

250 Amps

FLA: 131.2A | Busbar: 313 sq.mm Al / 209 sq.mm Cu

📘 Exhaustive Technical Engineering Reference Guide

1. Standard Equipment Power Ratings & Diversity Factors

Point / Equipment	Standard Wattage	Diversity Factor
LED Light Fixtures / Panels	36 W – 40 W per fixture (Downlights: 18W–20W)	0.80 – 0.90 (80% – 90%)
Ceiling Fans & Exhaust Fans	60 W – 75 W per point	0.70 – 0.80 (70% – 80%)
5A / 6A Power Sockets	100 W per point (Workstations: 250 W per PC)	0.60 – 0.65 (60% – 65%)
16A Power Socket Outlets	1000 W – 2000 W per point	0.50 – 0.65 (50% – 65%)
Air Conditioning (per TR / Ton)	1200 W – 1500 W / TR (Comfort AC baseline)	0.85 (Comfort) / 1.00 (Precision Data Center)
3-Phase Motors (per HP Rating)	746 W Mech. / ~850 W Elec. Input (~88% Eff.)	0.70 – 0.85 (Water Pumps) / 1.00 (Fire Pumps)

2. Power Factor Correction & APFC Sizing Mathematics

Uncorrected building inductive loads (motors, HVAC compressors, fluorescent ballasts) typically operate at a low power factor of 0.80 to 0.88 lagging. Installing Automatic Power Factor Correction (APFC) capacitor banks raises the operating power factor to 0.95+ lagging, reducing total apparent current (kVA) drawn from DISCOM utility lines and eliminating low PF penalty surcharges.

Required APFC Rating (kVAR) = Peak Active kW × [tan(arccos(PF_raw)) - tan(arccos(PF_target))]

• Active Demand (kW): P = Total Sum of (Quantity × Watts × Diversity %) / 1000
• Uncorrected kVA Demand: S_raw = P / PF_raw
• Corrected kVA Demand: S_corrected = P / PF_target

3. Transformer Sizing Methodology (Single Unit vs. N+1 Redundant Scheme)

In accordance with Substation Specifications, transformers should operate between 50% and 75% nominal rating under full design load to maximize operating efficiency and reduce thermal aging of winding insulation.

• Option A: Single Transformer (1 x TF): Selected such that Transformer Rating ≥ Peak Design kVA. Under full peak demand, the unit handles 100% of the building load.
• Option B: N+1 Redundant Scheme (2 x TF in Parallel): Two identical transformers are installed where each transformer is sized to handle at least 85% to 100% of the peak load independently:
  Required Unit Rating (kVA) = Peak Design kVA / 1.15
  During normal operation, both units share the building load at a safe 30% to 40% loading level. If one unit fails or undergoes scheduled maintenance, the remaining transformer sustains the full facility without blackout.

4. Emergency Diesel Generator (DG Set) Sizing Guidelines

NBC 2016 Part 4 & 8 mandates the segregation of operational facility backup loads from essential life-safety emergency infrastructure:

• Operational Facility Backup DG: Sized to support full building operational demand. DG set kVA is rated at maximum 80% prime running capacity:
  Main DG Rating (kVA) = Peak Design kVA / 0.80
• Emergency Life-Safety AMF DG: Dedicated exclusively to critical life-safety systems (Fire Main Hydrant Pumps, Sprinkler Jockey Pumps, Smoke Extraction Blowers, Fire Lifts, and Emergency Evacuation Lighting). Its automatic mains failure (AMF) transfer within 10 to 15 seconds.

5. Switchgear, Main Breaker & Busbar Sizing

The 3-phase full load current (FLA) determines the main incomer Air Circuit Breaker (ACB) or Molded Case Circuit Breaker (MCCB) rating and LT Panel busbar cross-sectional area:

Full Load Current (FLA Amperes) = (Peak Design kVA × 1000) / (1.73205 × Voltage)

• Incomer Breaker Multiplier: Main breaker is rated at 1.15 × FLA using standard frame sizes (250A, 400A, 630A, 800A, 1000A, 1250A, 1600A, 2000A, 2500A, 3200A).
• Aluminum Busbar Density : Maximum allowable current density is 0.8 Amps / sq.mm (Area_Al = Breaker Rating / 0.8).
• Copper Busbar Density : Maximum allowable current density is 1.2 Amps / sq.mm (Area_Cu = Breaker Rating / 1.2).