AHU Psychrometric & KPI Calculator | TheHVACLab Technologies

TheHVACLab Technologies

AHU Psychrometric & KPI Calculator

ASHRAE Compliant SI Units Field-Ready

ℹ Enter DB + RH (or DB + WB) for each state point. The calculator computes enthalpy, humidity ratio, ADP, BPF, SHR, and coil capacity. Minimum required: State Points 3 (Mixed Air) and 5 (Supply Air) for coil analysis.

State Point Inputs

Point	DB (°C)	RH (%)	WB (°C)

Airflow (CMH) m³/hour — used for capacity calculations

Altitude / Site Elevation (m) Affects atmospheric pressure & psychrometrics

Computed State Points

Enter values and click Calculate

Coil & System Analysis

ℹ TheHVACLab™ AEI Framework — 4 proprietary KPIs measurable with basic field instruments. Each KPI includes a benchmark range and RAG status.

KPI-1: AHU Efficiency Index (AEI)

Coil Cooling Capacity Q_coil (kW)

Supply Fan Power (kW)

CHW Pump Power (attributed, kW)

AEI = Q_coil / (Fan kW + Pump kW)

KPI-2: Coil Performance Index (CPI)

Entering Air DB (T_EAT °C)

Leaving Air DB (T_LAT °C)

Apparatus Dew Point (T_ADP °C)

CPI = (T_EAT – T_LAT) / (T_EAT – T_ADP) × 100%

KPI-3: Airflow Effectiveness Score (AES)

Actual Airflow Q_actual (CMH)

Design Airflow Q_design (CMH)

Filter ΔP — Clean Baseline (Pa)

Filter ΔP — Current (Pa)

AES = (Q_act/Q_des) × (ΔP_clean/ΔP_curr) × 100%

KPI-4: System Energy Intensity (SEI)

Total AHU kW Input (Fan + Pump + Aux)

Conditioned Floor Area (m²)

SEI = Total kW / Floor Area (m²) → W/m²

KPI Dashboard

ℹ Calculate Specific Fan Power (SFP), fan efficiency, VFD savings potential, and motor power from field measurements. ECBC / ASHRAE 90.1 benchmarks applied automatically.

Fan Power Inputs

Measured Voltage (V, line-line)

Measured Current (A, avg 3-phase)

Power Factor (PF)

Supply Airflow (CMH)

External Static Pressure — Design (Pa)

External Static Pressure — Measured (Pa)

Operating Hours / Year

Electricity Tariff (₹/kWh)

VFD Savings Estimator

Current Speed (% of design)

Target Speed after VFD (% of design)

Fan Power ∝ Speed³ (Affinity Law)
Savings % = 1 – (n_target/n_current)³

Fan Performance Results

ℹ Quantify energy penalties from 5 common AHU faults. Enter measured vs. design values — the calculator outputs kW penalty, annual kWh loss, and ₹ cost per fault.

Dirty Filter Penalty

Airflow (m³/s)

Clean Filter ΔP (Pa)

Current Filter ΔP (Pa)

Fan Efficiency η (0–1)

Motor Efficiency η (0–1)

Penalty = Q × ΔΔP / (η_fan × η_motor × 1000)

Over-Ventilation Penalty

Excess OA Flow (m³/s)

Outdoor Air Enthalpy h_OA (kJ/kg)

Return Air Enthalpy h_RA (kJ/kg)

Chiller COP

Penalty = ṁ_OA × (h_OA – h_RA) / COP
ṁ = Q × 1.2 kg/m³

Low ΔT CHW Syndrome Penalty

Design CHW ΔT (°C)

Actual CHW ΔT (°C)

Pump Design Power (kW)

Flow ratio = ΔT_des / ΔT_act
Extra pump kW ≈ Pump kW × (ratio² – 1) × 0.5

Excess SFP Penalty

Actual SFP (W/L/s)

Target SFP (W/L/s) [ECBC = 1.5]

System Airflow (L/s)

Penalty = (SFP_act – SFP_target) × Airflow (L/s) / 1000

Common Parameters

Annual Operating Hours

Electricity Tariff (₹/kWh)

Energy Penalty Summary

ℹ Enter live field measurements and the FDD engine will auto-flag faults against 20 diagnostic rules. Rules are prioritized by energy impact.

Airflow & Pressure

Actual Airflow (% of design)

ESP Measured (Pa)

ESP Design (Pa)

Filter ΔP Actual / Clean ratio

SFP (W/L/s)

3-phase Current Imbalance (%)

Temperature & Coil

SAT vs Setpoint offset (°C)

Bypass Factor (BPF)

CHW ΔT Actual (°C)

CHW ΔT Design (°C)

Valve downstream temp — closed (°C above ambient)

Motor surface temp rise (°C)

Ventilation & Controls

CO₂ in Return Air (ppm)

Space RH (%)

Mixed Air Temp deviation (°C)

SAT oscillation amplitude (°C)

Is heating coil active while cooling? (1=yes)

Diagnostic Results

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