Industrial Connected Load Calculator

An industrial connected load calculation establishes the installed electrical load represented by a process-equipment inventory. The calculator totals connected real power in kW, converts each row to apparent power in kVA using its power factor, and calculates the current associated with the selected system voltage and phase basis.

The resulting Connected load, Connected apparent load, and Connected current screen provide an electrical starting point for preliminary feeder review, transformer load review, service load inventory, raceway planning, voltage-drop evaluation, and equipment scheduling. The result is based on installed connected equipment—not an operating-demand calculation, motor branch-circuit calculation, or overcurrent protective-device selection.

Use the inventory screen before a separate demand, feeder, transformer, or protection review.

Equipment Inventory Inputs

Each entry under Industrial equipment rows represents one equipment type or process load. Connected power should come from a manufacturer nameplate, equipment schedule, approved submittal, motor data, heater rating, or other documented source.

Field	Electrical use
Equipment label	Identifies the process load or equipment group, such as a motor, heater bank, compressor, conveyor, or controls cabinet.
Quantity (units)	Multiplies the connected power for identical installed units.
Connected power per unit (kW)	Real power rating assigned to one unit of equipment.
Power factor (%)	Converts real power to apparent power. Resistive heating is commonly entered as 100% when its documented power factor is unity.
System voltage (V)	Supplies the voltage basis for the current calculation.
Phase	Sets the current-arithmetic basis. The example uses Balanced three-phase.
Inventory note	Records manufacturer, model, source, duty, and process group separately from the electrical arithmetic.

A process motor should not be entered from an assumed horsepower-to-kW conversion when documented electrical input data is available. The connected-power value should represent the actual basis used by the project electrical design.

kW, kVA, and Connected Current

Connected load is the sum of all installed real-power entries:

\(\displaystyle \text{Connected load (kW)}=\sum(\text{Quantity}\times\text{Connected power per unit}\)

Connected apparent load accounts for power factor on each equipment row:

\(\displaystyle \text{Row apparent load (kVA)}= \frac{\text{Quantity}\times\text{Connected power per unit (kW)}}{\text{Power factor}/100}\)

\(\displaystyle \text{Connected apparent load (kVA)}=\sum\text{Row apparent load (kVA)}\)

For the Balanced three-phase selection, the calculator derives current from total apparent load:

\(\displaystyle \text{Connected current screen (A)}= \frac{\text{Connected apparent load (kVA)}\times1{,}000} {\sqrt{3}\times\text{System voltage (V)}}\)

kW represents the real power consumed or converted to work and heat. kVA represents the apparent power that drives source, transformer, feeder, and current calculations. A lower power factor increases kVA and current for the same connected kW.

The calculation applies power factor row by row rather than applying a single blended value to the total connected kW. That approach preserves the electrical effect of mixed loads such as motors, heating, drives, and controls.

Calculation Example

For a 480 V balanced three-phase process inventory:

Equipment label	Quantity	Connected power per unit	Power factor	Extended load	Apparent load
Process motor	2	15 kW	85%	30 kW	35.2941 kVA
Heater bank	1	20 kW	100%	20 kW	20.0000 kVA
Controls	1	2 kW	95%	2 kW	2.1053 kVA
Total				52 kW	57.3994 kVA

The connected current for the 480 V balanced three-phase inventory is:

\(\displaystyle I=\frac{57.3994\times1{,}000}{\sqrt{3}\times480}\)

\(\displaystyle \mathbf{I=69.0407\ A}\)

The calculator therefore reports:

• Connected load: 52 kW
• Connected apparent load: 57.3994 kVA
• Connected current screen: 69.0407 A
• Largest row load: 30 kW
• Counted equipment rows: 3 rows

The Largest row load identifies the largest quantity-extended real-power row in the inventory. In this example, two 15 kW Process motor units produce a 30 kW row load. It is useful for identifying a major process group for later motor, feeder, voltage-drop, or startup review, but it does not identify the largest individual motor or establish a motor-feeder sizing rule.

Design and Field Boundaries

The connected-current result is an inventory current at the entered voltage and selected phase basis. It does not establish final conductor size in AWG or kcmil, raceway fill, breaker or fuse size, transformer rating, or generator capacity.

Final installation design requires a separate review of the applicable conditions, including:

• Equipment duty, simultaneous operation, process sequence, and demand treatment.
• Motor full-load current, starting method, largest-motor treatment, and branch-circuit requirements.
• Continuous-load treatment where applicable.
• Conductor ampacity after insulation temperature rating, terminal rating, ambient-temperature correction factor, and adjustment factor for current-carrying conductors.
• Feeder and branch-circuit voltage drop at actual conductor length, conductor material, conductor size, and load characteristics.
• Raceway fill, conductor bending space, pulling conditions, termination space, and physical layout.
• Available fault current, short-circuit current rating, overcurrent protection, disconnecting means, and equipment SCCR.
• Project drawings, manufacturer instructions, utility requirements, and the requirements enforced by the local AHJ.

For unbalanced three-phase systems, substantial nonlinear loads, variable-frequency drives, intermittent loads, or equipment with uncertain power factor, the installation should be evaluated from actual equipment electrical data and the applicable design method rather than treating the balanced connected-current value as a phase-by-phase field measurement.