Continuous Load Calculator

A continuous load calculator determines the adjusted current created when a defined portion of an electrical load receives a continuous-load multiplier. The adjusted current is the load value used when reviewing conductor ampacity, branch-circuit or feeder loading, overcurrent-device selection, voltage-drop calculations, and related load documentation.

The calculation separates the entered load into its continuous and noncontinuous portions. It applies the Continuous multiplier only to the percentage identified in Continuous portion, then combines both portions into one adjusted current.

This prevents a common load-calculation error: applying the multiplier to the entire load when only part of the load is continuous.

Adjusted Current

Enter Load current as the actual operating current before any continuous-load treatment. Enter Continuous portion to identify what percentage of that current receives the Continuous multiplier.

The calculator returns:

Result	Electrical meaning
Continuous current	The portion of Load current identified as continuous
Noncontinuous current	The remaining portion of Load current not multiplied
Adjusted current	Continuous current after the multiplier, plus noncontinuous current
Connected load	Apparent power represented by the original Load current
Adjusted load	Apparent power represented by the Adjusted current
Entered ampacity margin	Entered ampacity minus Adjusted current

For conductor sizing, the Adjusted current is the key result. It is not automatically a final conductor ampacity selection. The selected conductor still has to be evaluated for its allowable ampacity after applicable terminal limitations, insulation temperature rating, ambient-temperature correction, current-carrying-conductor adjustment factors, and installation conditions.

Calculation Method

The calculator uses the following arithmetic:

\(\text{Continuous current} = \text{Load current} \times \left(\frac{\text{Continuous portion}}{100}\right)\)

\(\text{Noncontinuous current} = \text{Load current} - \text{Continuous current}\)

\(\text{Adjusted current} = \left(\text{Continuous current} \times \left(\frac{\text{Continuous multiplier}}{100}\right) \right) + \text{Noncontinuous current}\)

For apparent power, the calculator uses System voltage and the selected Phase:

\(\text{Single-phase VA} = V \times I\)

\(\text{Balanced three-phase VA} = \sqrt{3} \times V \times I\)

The calculator applies the applicable VA equation twice:

• Connected load uses Load current.
• Adjusted load uses Adjusted current.

If Entered ampacity is provided, the available margin is:

\(\text{Entered ampacity margin} = \text{Entered ampacity} - \text{Adjusted current}\)

A positive margin indicates that the entered ampacity exceeds the calculated adjusted current. A zero or negative margin indicates that the entered ampacity does not exceed it.

Calculation Example

For a single-phase load with the following values:

Input	Value
Load current	32 A
Continuous portion	100%
Continuous multiplier	125%
System voltage	240 V
Phase	Single-phase
Entered ampacity	50 A

All 32 A is identified as continuous:

\(32\text{ A} \times 100\% = 32\text{ A continuous current}\)

There is no noncontinuous portion:

\(32\text{ A} - 32\text{ A} = 0\text{ A noncontinuous current}\)

Apply the 125% multiplier:

\(32\text{ A} \times 125\% = 40\text{ A adjusted current}\)

Calculate apparent power:

\(240\text{ V} \times 32\text{ A} = 7{,}680\text{ VA connected load}\)

\(240\text{ V} \times 40\text{ A} = 9{,}600\text{ VA adjusted load}\)

The entered ampacity margin is:

\(50\text{ A} - 40\text{ A} = 10\text{ A}\)

The resulting values are:

• Continuous current: 32 A
• Noncontinuous current: 0 A
• Adjusted current: 40 A
• Connected load: 7,680 VA
• Adjusted load: 9,600 VA
• Entered ampacity margin: 10 A

Conductor and Raceway Review

Use the adjusted current as a load input when evaluating a branch circuit or feeder. For example, it can be compared with the allowable ampacity of a proposed AWG or kcmil conductor after the installation-specific ampacity review is complete.

The same adjusted current can support related electrical calculations:

• Conductor ampacity comparison after applying the required correction factor and adjustment factor
• Feeder and branch-circuit load schedules
• Voltage-drop calculations using the actual conductor material, conductor size, circuit length, and load current
• Raceway-fill planning after conductor quantity and conductor sizes are selected
• Equipment loading review when the available ampacity is known
• Load comparison for single-phase or balanced three-phase systems

System voltage and Phase affect the VA results, not the adjusted-current arithmetic. A 32 A load with a 100% continuous portion and 125% multiplier produces 40 A adjusted current regardless of whether the VA conversion is single-phase or balanced three-phase.

Field Verification

The calculator performs transparent continuous-load arithmetic from the values entered. Final electrical design and installation decisions require separate verification of the actual load characteristics and applicable requirements.

Confirm the continuous portion from the equipment duty cycle and intended operation. Then verify the conductor’s allowable ampacity using the applicable conductor insulation temperature rating, terminal rating, ambient conditions, number of current-carrying conductors, raceway or cable installation method, and any required correction or adjustment factors.

For three-phase input, select Balanced three-phase only when the VA conversion is appropriate for a balanced line-to-line load. Unbalanced loads, nonlinear loading, neutral loading, motor starting conditions, and equipment-specific instructions require separate engineering or field evaluation. Coordinate the final conductor, overcurrent protection, disconnecting means, and equipment ratings with the adopted electrical code and the AHJ.