MEP Calculator

1. Power Triangle & Current

S = √3·V·I · P = S·cosφ · Q = S·sinφ · S = √(P²+Q²)

Fill in known values only. At least 2 values required.

Voltage (V)

Current (A)

Active Power (kW)

Apparent Power (kVA)

cos φ

Phase

Result

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2. Breaker & Cable Sizing

In = P/(√3·V·cosφ) → ×125% → select breaker & cable ampacity

Power (kW)

Voltage (V)

cos φ

Phase

Installation safety (%)

Result

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3. Voltage Drop

3φ: ΔU = √3 · I · (R cosφ + X sinφ) · L/1000

Phase

Voltage (V)

Current (A)

Length (m)

R (Ω/km)

X (Ω/km)

cos φ

Result

—

Max limit: Lighting 3% | Other loads 5% | General 4%

4. Capacitor Bank

Qc = P × (tan φ₁ − tan φ₂)

Power (kW)

Initial cos φ

Target cos φ

Result

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5. Cable Resistance

R = ρ / S × L/1000

Cross-section (mm²)

Length (m)

Material

Result

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6. Transformer & Genset Sizing

S trafo = ΣP × 1.2 · P genset = ΣP × DF / cosφ × 1.2

Total Power (kW)

Demand Factor

cos φ

Result

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7. Number of Light Fixtures

N = (E × A) / (η × Q × d) · Q = lm/W × Watt

Lux (E)

Area (m²)

η (efficiency)

d (depreciation)

lm/W

Watt/fixture

Result

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8. Short Circuit Current (Isc)

Isc ≈ (S × 1000) / (√3 × V × uk/100)

Transformer Capacity (kVA)

Voltage (V)

uk (%)

Result

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1. Room AC Capacity

Q = 0.59 × W × L × H × I × E (Btu/h)

Width (m)

Length (m)

Height (m)

Insulation Factor (I)

Orientation Factor (E)

Safety factor (%)

Result

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I: 10 (insulated) / 18 (not insulated). E: 16 north, 17 east, 18 south, 20 west.

2. AC Power Consumption

P = (Btu/h / 9000) × 746 × 1.3

Capacity (Btu/h)

Result

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3. Refrigerant Pipe Size

Lookup based on capacity (PK)

Capacity (PK)

Result

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Gas pipe is always larger than liquid. For VRF / length > 15m check manufacturer manual.

4. Duct Sizing

A = Q / v

Air flow

Unit

Velocity (m/s)

Result

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5. Number of Diffusers / Grilles

S = (Q × 472) / (p × l × v)

Air flow (CFM)

Diffuser width (mm)

Diffuser length (mm)

Velocity (m/s)

Result

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6. AHU / FCU Fan Power

P = Q × 1.7 × (ΔP + v²×0.6) / (η × 3600)

Air flow (CFM)

Pressure Drop (Pa)

Outlet velocity (m/s)

Fan efficiency

Result

—

AHU typically 375 Pa (1.5 inWg), FCU 250 Pa.

7. CHWS/R Pump Capacity

Q = X × QAC (TR)

Chiller Capacity (TR)

Chiller Type

Pump safety (%)

Result

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1. Plumbing Pipe Diameter

d = √( (200 × Q) / (3 × π × v) )

Flow rate (LPM)

Velocity (m/s)

Result

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Typical velocity: distribution 1–2 m/s · suction 0.6–1.2 m/s · discharge 1.5–3 m/s

2. Plumbing Pump Head

H = Lv + (Lt × f) + Pf + safety%

Vertical Height Lv (m)

Total Pipe Length Lt (m)

Friction factor f (m/m)

Fixture Pressure Pf (m)

Safety (%)

Result

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Typical Pf: faucet 3–5 m · shower 7–10 m · flush valve 10–15 m

3. Plumbing Pump Power

P = (0.163 × H × Q × f) / η

Head (m)

Flow rate (LPM)

Efficiency η

Motor factor

Power safety (%)

Result

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4. Ground Tank Capacity

Estimate volume based on daily demand

Water demand (liters/day)

Operating hours

Storage safety (%)

Result

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1. Fire Pump Capacity

Sprinkler 80 LPM/point · IHB 400 LPM · Pillar 1000 LPM

Number of Sprinkler Points

Number of IHB

Number of Hydrant Pillars

Jockey (%)

Design margin (%)

Result

—

2. Fire Pump Head

H = Lvert + Ljauh×f + (Phyd + Pspr)×10

Vertical Height (m)

Farthest Distance (m)

Friction factor f

Hydrant Pressure (bar)

Sprinkler Pressure (bar)

Result

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3. Fire Pump Power

P = 0.163 × H × Q(LPS) × SF / η

Head (m)

Flow rate (LPM)

Efficiency η

Safety Factor (multiplier)

Result

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4. Fire Tank Capacity

V = Q × t × conversion

Pump Flow Rate

Unit

Duration (minutes)

Result

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5. Fire Pipe Diameter

d = √(200 × Q / (3 × π × v))

Flow rate (LPM)

Velocity (m/s)

Result

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Typical fire pipe velocity: 3.0 – 4.5 m/s

6. Sprinkler Pipe Size

Recommended pipe based on sprinkler points

Sprinkler points

Flow per point (LPM)

Result

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Example: 1 sprinkler point typically uses Ø25 mm.

1. Speaker SPL & Count

SPL = Sensitivity + 10·log₁₀(Power) - 20·log₁₀(Distance) + 10·log₁₀(Count)

Speaker sensitivity (dB @ 1W/1m)

Power per speaker (W)

Distance to listener (m)

Number of speakers

Desired SPL target (optional dB)

Required margin (dB)

Result

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The calculator estimates SPL from speaker sensitivity, power, distance, and speaker count.

BTU/h → PK / TR

BTU/h

Result

—

PK → Watt

PK

Result

—

m³/h → CFM

m³/h

Result

—

CFM → L/s

CFM

Result

—

Watt → Ampere

Watt

Voltage (V)

Phase

Result

—

Length Converter (mm ↔ cm ↔ m ↔ in)

Value

Unit

Result

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1. Power Triangle & Current

Result

2. Breaker & Cable Sizing

Result

3. Voltage Drop

Result

4. Capacitor Bank

Result

5. Cable Resistance

Result

6. Transformer & Genset Sizing

Result

7. Number of Light Fixtures

Result

8. Short Circuit Current (Isc)

Result

1. Room AC Capacity

Result

2. AC Power Consumption

Result

3. Refrigerant Pipe Size

Result

4. Duct Sizing

Result

5. Number of Diffusers / Grilles

Result

6. AHU / FCU Fan Power

Result

7. CHWS/R Pump Capacity

Result

1. Plumbing Pipe Diameter

Result

2. Plumbing Pump Head

Result

3. Plumbing Pump Power

Result

4. Ground Tank Capacity

Result

1. Fire Pump Capacity

Result

2. Fire Pump Head

Result

3. Fire Pump Power

Result

4. Fire Tank Capacity

Result

5. Fire Pipe Diameter

Result

6. Sprinkler Pipe Size

Result

1. Speaker SPL & Count

Result

BTU/h → PK / TR

Result

PK → Watt

Result

m³/h → CFM

Result

CFM → L/s

Result

Watt → Ampere

Result

Length Converter (mm ↔ cm ↔ m ↔ in)

Result

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