Motor Disconnect Size Calculator
Use this motor disconnect workflow for early current-rating comparison when motor FLA, multiplier, entered disconnect rating, voltage, and phase are known.
- Required disconnect current
- A
- Entered disconnect margin
- A
- Motor load
- kVA
- Rating status
Calculation details
- Calculation basis
- Selection boundary
Recent results
Formulas
- Required disconnect current = motor FLA x disconnect multiplier percent / 100
- Entered disconnect margin = entered disconnect rating amps - required disconnect current amps
- Motor load kVA = motor FLA x voltage x phase multiplier / 1000
Use this calculator
Estimate required disconnect current, entered disconnect margin, motor load kVA, and rating status from entered motor and disconnect assumptions.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This motor disconnect estimate uses user-entered comparison values. It does not apply horsepower tables, select disconnects, verify enclosure or SCCR, or prove code compliance.
FAQs
Does this choose a disconnect switch?
No. It only compares current values. Final disconnect selection needs horsepower rating, enclosure, SCCR, listing, and code review.
Where should the multiplier come from?
Use the project, manufacturer, or reviewer basis. The calculator does not choose a code multiplier.
Can this approve a motor disconnect?
No. It is an arithmetic screen, not equipment selection or approval.