HVAC Electrical Calculators | Chiller Trend
Electrical Calculators
Electrical calculators for quick field checks.
Enter two values to calculate the other two.
Known Values
Advanced
Formula: V = I × R. P = V × I. Related forms are used depending on which two values are entered.
Assumptions: Ideal DC and simple resistive-circuit relationships.
Warnings: Measure resistance only on a de-energized circuit. Motors, coils, transformers, and drives require additional electrical relationships.
Estimate real power from voltage, current, and power factor.
Electrical Readings
Enter line voltage and line current. Replace the default power factor if measured.
Advanced
Formula: kW = volts × amps × 1.732 × power factor ÷ 1000.
Assumptions: Voltage and current are treated as balanced three-phase line values.
Warnings: If power factor is estimated instead of measured, calculated kW is also estimated.
Calculate current imbalance from three phase-current readings.
Phase Current
Enter L1, L2, and L3 current.
Advanced
Formula: % imbalance = maximum deviation from average ÷ average current × 100.
Assumptions: All three readings are taken under the same operating condition and are directly comparable.
Warnings: Verify readings with a calibrated meter and compare against equipment-manufacturer limits.
Calculate synchronous motor speed and nameplate slip.
Motor and VFD
Enter VFD frequency and motor poles. Add nameplate full-load RPM to calculate nameplate slip.
Advanced
Formula: Synchronous RPM = 120 × frequency ÷ poles. Base synchronous RPM = 120 × base frequency ÷ poles. Slip RPM = base synchronous RPM − nameplate full-load RPM. Slip % = slip RPM ÷ base synchronous RPM × 100.
Assumptions: Nameplate slip describes the rated full-load condition at the motor base frequency.
Warnings: Actual shaft RPM under load depends on operating load, motor characteristics, and VFD control behavior. This calculator does not predict actual loaded shaft RPM at arbitrary VFD frequencies.
Calculate required VA or available control current.
Transformer Inputs
Choose what to calculate, then enter the requested values.
Advanced
Formula: VA = volts × amps. Amps = VA ÷ volts.
Assumptions: This uses the basic single-phase volt-ampere relationship for transformer secondary loads.
Warnings: The result does not add sizing margin or account for inrush, duty cycle, simultaneous loads, fuse sizing, conductor sizing, or manufacturer requirements.