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NFPA 70 workflowNo automatic breaker selection

OCPD Load-Basis
Comparison Worksheet

Calculate a load basis from user-classified loads and a verified multiplier. Optionally compare a selected OCPD rating with that basis and an entered equipment/conductor maximum.

Who it's for: electrical engineers and contractors reconciling a load basis at construction documents, after loads are classified and any multiplier is verified.

The former automatic selection was removed
The prior page universally rounded to an embedded standard-size list and suggested conductor size. Those steps require conditions the form did not collect.
Entered load basis
A

How to use this calculator

1
Classify the loads outside this worksheet
Confirm circuit or feeder scope, what is continuous, simultaneous operation, and every equipment-specific rule in the adopted edition.
2
Enter the verified factor
Use the multiplier established by the applicable provision. Do not assume 1.25 when a listed 100%-rated assembly or another article changes the treatment.
3
Enter selection and maximum only when verified
The selected rating and conductor/equipment maximum are optional comparisons; the worksheet does not select either value.

The formula

Arithmetic load basis = noncontinuous load + continuous load × entered verified factor.
No standard-size rounding, next-size allowance, conductor lookup, or equipment rule is embedded.

Worked example

Example
For 32 A continuous, 8 A noncontinuous, and a verified factor of 1.25, the arithmetic basis is 48 A. An entered 50 A device is above that basis, but is acceptable only if all conductor, equipment, listing, standard-rating, and specific-article conditions independently permit it.

When this estimate will be off

  • Does not determine whether a load is continuous, which factor applies, or whether a 100%-rated exception is satisfied.
  • Does not apply standard OCPD ratings or the conditional next-higher-size rule.
  • Does not determine conductor ampacity, terminal temperature limits, small-conductor rules, motor/HVAC/EV or other equipment protection, fault duty, selective coordination, or local amendments.
  • A numerical comparison is not a design, approval, or installation instruction.

Frequently asked questions

A common mistake: Does not determine whether a load is continuous, which factor applies, or whether a 100%-rated exception is satisfied.

Standard-rating and next-size provisions are conditional, and equipment, conductor, circuit type, listing, and specific articles can control. The worksheet compares only values you verified.

No. Verify the applicable adopted provision and exceptions. The editable field prevents the worksheet from silently deciding that question.

No. It addresses only the entered arithmetic basis and optional entered cap; all other design and code checks remain outside scope.

Sources

This free Circuit Breaker Size Calculator is built and maintained by DataDrivenAEC, using the relevant codes and standards. It does not substitute for professional judgment.