Engineering Derivation Engine

Interactive MEP Sizing Calculators

Accurate engineering calculations conforming to ASHRAE, ISHRAE, NFPA 13, and IEEE standards.

ASHRAE Standard 90.1 / CLTD Method

Space Cooling Load & Chiller Tonnage

Computes thermal heat gain across envelope, occupants, plug loads, and fresh air supply.

Quick Presets:

Floor Area (sq. ft.)

Occupancy Type

Peak Occupant Count

Equipment Load (Watts)

📐 Show Engineering Formula & Math Derivation

• Total Heat Gain (Q) = Q_area + Q_occupants + Q_equipment

• Q_area = Area × Base_BTU/sq.ft

• Q_occupants = Occupants × 450 BTU/person (Sensible + Latent)

• Q_equipment = Watts × 3.412 BTU/Watt

• Tonnage (TR) = Q_total / 12,000 BTU/h • Airflow = TR × 400 CFM

Calculation Results ASHRAE 90.1

Estimated Cooling Capacity

12.5 TR

(43.9 kW Cooling)

Supply Airflow

5,000 CFM

Total Heat Gain

149,930 BTU/h

SMACNA HVAC Duct Construction Standards

Equal Velocity Air Duct Sizing (Rectangular & Round)

Converts airflow volume into cross-sectional duct dimensions and equivalent diameter.

Airflow Volume (CFM)

Target Velocity (FPM)

Aspect Ratio (Width : Height)

📐 Show SMACNA Duct Formula Derivation

• Duct Area (sq. ft) = CFM / Velocity (FPM)

• Duct Area (sq. in) = Duct Area (sq. ft) × 144

• Height (in) = √(Area_sq_in / Aspect_Ratio) • Width = Height × Aspect_Ratio

• Round Equivalent Diameter = √[(4 × Area_sq_in) / π]

Duct Dimensions SMACNA

Rectangular Duct Size (W × H)

24" × 16"

(384 sq. inches / 2.67 sq. ft)

Equivalent Round Duct Diameter

22.1" Ø

Hydraulic Institute (HI) & Darcy-Weisbach

Pump Total Dynamic Head (TDH) & Motor Power

Calculates static lift, friction head loss, and hydraulic brake horsepower.

Flow Rate (GPM)

Static Elevation Head (Feet)

Total Pipe Run (Feet)

Friction Loss (Ft / 100ft)

Residual Terminal Pressure (PSI)

Hydraulic Efficiency (%)

📐 Show Hydraulic TDH Formula Derivation

• TDH = Static_Head + Pipe_Friction_Head + Residual_Head

• Friction_Head = (Length / 100) × Friction_rate • Residual_Head = PSI × 2.31 Ft

• Water Horsepower (WHP) = (GPM × TDH) / 3,960

• Brake Horsepower (BHP) = WHP / (η / 100) • Motor kW = BHP × 0.7457

Hydraulic Sizing Hydraulic Inst

Total Dynamic Head (TDH)

86.7 Ft

(26.4 meters / 2.59 bar)

Brake Horsepower

9.83 HP

Motor Power (kW)

7.33 kW

IEC 60364 / IEEE 141 / IS 732 Standards

3-Phase Cable Sizing & Voltage Drop Calculator

Computes full load current, voltage drop percentage, and conductor compliance.

Connected Load (kW)

System Line Voltage (V)

Power Factor (cos φ)

Run Length (Meters)

Conductor Material

📐 Show 3-Phase Cable Math & Voltage Drop Formula

• Full Load Current (I) = (kW × 1,000) / [√3 × V × cos(φ)]

• Voltage Drop (V_drop) = [√3 × I × L × ρ × cos(φ)] / Area_sq_mm

• % Voltage Drop = (V_drop / V_nominal) × 100% (Must be ≤ 3.0% per NEC/IS 732)

Electrical Compliance IEC 60364

Recommended Cable Cross-Section

70 sq.mm

Full Load Current: 122.8 Amps

Voltage Drop

3.83 Volts

% Voltage Drop

0.92% (Pass)

AHRI Standard 550/590 & ASHRAE 90.1

Chiller Efficiency, COP & kW/TR Benchmarking

Evaluates specific power consumption against international green building standards.

Rated Tonnage (TR)

Electrical Input (kW)

📐 Show Chiller COP & kW/TR Formula Derivations

• kW/TR = Measured_kW / Rated_TR

• Coefficient of Performance (COP) = 3.51685 / (kW/TR)

• Energy Efficiency Ratio (EER) = 12 / (kW/TR) = COP × 3.412

• ASHRAE 90.1 Path B Limit: kW/TR ≤ 0.58 at Full Load AHRI Conditions

Chiller Performance AHRI 550/590

Specific Power Consumption

0.600 kW/TR

✓ Compliant with ASHRAE 90.1 Path B

Coefficient of Perf. (COP)

5.86

Energy Efficiency Ratio

20.00 EER

NFPA 13 Density / Area Hydraulic Method

NFPA 13 Fire Sprinkler & Hose Stream Demand

Sizes municipal fire pump head flow and 60-minute static reservoir water storage.

Hazard Classification

Hydraulic Remote Area (sq. ft.)

Hose Stream Demand (GPM)

📐 Show NFPA 13 Fire Flow Derivation

• Sprinkler Demand = Remote_Area × Density × 1.15 (Over-discharge allowance)

• Total Fire Demand = Sprinkler_Demand + Hose_Stream_Allowance

• 60-Minute Water Storage Tank = Total_GPM × 60 mins × 0.003785 m³/gal

Fire Water Demand NFPA 13

Total Fire Pump Flow Demand

595 GPM

(135.1 m³/hr / 2,252 LPM)

Sprinkler Demand

345 GPM

60-Min Tank Volume

135 m³

MEP Engineering Sizing Calculators & Sizing Sheets