Sizing warnings and errors

The NEC sizing engine validates component data and displays warnings when sizing rules cannot be applied or results may be non-compliant.

Understanding sizing issues

Errors (blocking):

Prevent sizing calculation from running
Must be fixed before sizing completes
Indicate missing required data or invalid values
Shown in red with error icon

Warnings (non-blocking):

Sizing completes but results may need review
Indicate potential NEC violations or edge cases
Shown in yellow with warning icon
Results may require engineering judgment

Common sizing status messages

Some frequently seen sizing messages are status indicators rather than warnings or errors:

The last sizing result is historical evidence for a recommendation. A current selection status comes from Recheck, which reads the installed values and current project or scenario facts without writing them. Manual and locked components remain eligible for that check, and a recommendation difference alone is not a failure.

"Pending sizing suggestions":

Meaning: The editor has calculated proposed changes that have not been accepted yet
What to do: Review the green suggestions and accept or dismiss them

"No sizing results available.":

Meaning: No persisted sizing run has been stored for that component yet
What to do: Use Re-size system to generate detailed sizing results

"Sizing details are stale.":

Meaning: The saved sizing details no longer match the current live component values
What to do: Use Re-size system to refresh the stored sizing explanation

Accepted value changed but details still show old calculation:

Meaning: Most accepted bus, cable conductor, cable parallel-run, and protection-device rated-current suggestions refresh sizing details after writing the value. Transformer accepted values, or unexpected refresh failures, can still leave details stale.
What to do: Use Re-size system when you need the detailed card to match the accepted value.

Coordinated sizing group could not be applied:

Meaning: A linked main/aggregate breaker, protected bus, or protected-conductor group failed validation.
Cause: One linked member is stale, missing, not in Auto mode, topology-changed, or cannot map to an active cable variant.
Solution: Refresh sizing suggestions, set required members to Auto if appropriate, select a cable series if needed, then accept the group again.

Common sizing errors

Missing conductor data:

Error: "Cable variant not specified"
Cause: Cable component created without selecting cable type
Solution: Select cable series and variant from dropdown

Invalid current value:

Error: "Load current must be greater than zero"
Cause: Load power set to zero or negative
Solution: Enter valid load power (MW or MVAR)

Missing voltage:

Error: "Rated voltage required for sizing"
Cause: Component voltage field empty
Solution: Enter voltage rating in kV

Incompatible installation type:

Error: "Installation type not supported for this cable"
Cause: Selected installation method invalid for cable type
Solution: Choose compatible installation (underground, cable tray, etc.)

Conductor size below minimum:

Error: "Conductor cannot be smaller than #14 AWG"
Cause: Calculated ampacity requires conductor smaller than code minimum
Solution: Verify load current is realistic; minimum #14 for branch circuits

Required rating exceeds the available catalog:

Error: "Required rating exceeds the largest available standard rating"
Cause: The calculated bus, transformer, breaker, fuse, or switch requirement is larger than the active catalog supports
Solution: Add/select suitable equipment data or reduce the design load. Auto-sizing preserves the current value and does not silently select the largest undersized catalog item.

Feeder voltage mismatch:

Error: "Downstream load voltage is incompatible with the feeder voltage"
Cause: A reachable load is connected at a voltage that cannot be supplied directly or through a normal line-to-neutral/split-phase relationship
Solution: Correct the component voltage or add the required transformer. Auto-sizing blocks the affected feeder, bus, or aggregate protective-device proposal.

Protection constraint conflict:

Error: "Required OCPD rating exceeds cable ampacity" or a configured maximum
Cause: The true load requirement cannot be satisfied by the protected conductor or explicit device limit
Solution: Increase the conductor or allowed device rating, or reduce the load. Auto-sizing preserves the true requirement and blocks the proposal instead of rounding it down.

For motor branches, the short-circuit and ground-fault device is not capped at the NEC 430.22 conductor ampacity; NEC 240.4(G) routes that protection to Article 430. A user-entered maximum remains a hard constraint and blocks an incompatible proposal.

Common sizing warnings

High ambient temperature:

Warning: "Ambient temperature exceeds NEC table range"
Cause: Ambient temperature >50°C (122°F)
Impact: May require custom derating factors
Solution: Verify temperature is accurate; use custom reference tables if needed

High conductor count:

Warning: "More than 40 conductors in raceway"
Cause: Bundling adjustment factor table limit reached
Impact: 40% derating applied; may need larger conductor
Solution: Reduce conductors per raceway or use multiple raceways

Next size up applied:

Warning: "OCPD sized to next standard rating"
Cause: The conductor ampacity falls between standard ratings and all NEC 240.4(B) conditions are satisfied
Impact: Slightly oversized protection
Solution: Normal only when the load does not exceed conductor ampacity, the device is 800 A or less, and no lower explicit user maximum controls. Ordinary rounding that remains within conductor ampacity is a standard NEC 240.6(A) selection, not this exception.

Motor starting current high:

Warning: "Starting current exceeds OCPD rating"
Cause: Motor FLC × starting multiplier > OCPD
Impact: May nuisance trip on start
Solution: Use higher OCPD multiplier (within NEC limits) or soft start

Voltage drop exceeds recommendation:

Warning: "Voltage drop >3% (NEC recommendation)"
Cause: Long cable run or high current
Impact: May cause equipment performance issues
Solution: When length, voltage, power factor, and cable R/X data are available, auto-sizing can propose a larger conductor to satisfy the voltage-drop limit. Otherwise, add the missing cable data, increase conductor size manually, or reduce run length.

Parallel conductor required:

Warning: "Single conductor insufficient, parallel runs required"
Cause: Load exceeds largest single conductor ampacity
Impact: Need multiple conductors per phase
Solution: System automatically calculates parallel runs when auto-parallel is enabled; verify acceptable

Auto-parallel applied:

Not a warning. Auto-parallel is a successful sizing decision.
Cause: Auto-parallel sizing determined that multiple parallel runs are needed to keep conductor size at or below the configured threshold.
Impact: Cable parallel runs have been updated automatically.
Review: Check the selected configuration in the cable sizing details. Adjust auto-parallel settings in Sizing Defaults if the result is undesirable. See Auto-parallel sizing.

Cable series not selected:

Warning: "Cable has no series selected. Select a cable series to enable auto-sizing."
Cause: The cable has no cable series assigned, so auto-sizing cannot apply a cable variant
Impact: Conductor size is calculated but no cable variant is applied to the cable
Solution: Select the cable on the canvas and choose a cable series from the dropdown in the edit panel

Motor sizing warnings

FLC not in table:

Warning: "Motor HP not in NEC table, interpolated value used"
Cause: Non-standard motor size (e.g., 7.5 HP at 460V)
Solution: Verify motor nameplate FLA; may need to enter custom value

High OCPD multiplier:

Warning: "Motor OCPD at maximum NEC multiplier"
Cause: 2.5× FLC for inverse time breaker or 1.75× for fuse
Impact: May not protect motor adequately
Solution: Verify motor starting characteristics; consider soft start

Service factor mismatch:

Warning: "Motor service factor >1.15"
Cause: Nameplate service factor allows higher continuous current
Impact: Sizing based on NEC FLC, not nameplate
Solution: If using higher service factor, size conductors manually

Cable sizing warnings

Temperature termination limit:

Warning: "Conductor derated to 75°C termination temperature"
Cause: Using 90°C conductor on 75°C rated terminal
Impact: Cannot use full 90°C ampacity
Solution: Normal per NEC 110.14(C); already applied correctly

Derating below 50%:

Warning: "Combined derating factors <0.50"
Cause: High ambient temperature + many conductors
Impact: Need significantly larger conductor
Solution: Reduce ambient exposure or bundled conductors; verify necessary

Continuous load factor:

Warning: "125% continuous load factor applied"
Cause: Load marked as continuous (operates 3+ hours)
Impact: Conductor and OCPD sized at 125% of load
Solution: Normal for continuous loads; verify load actually continuous

OCPD sizing warnings

Exceeds conductor ampacity:

Error: "OCPD rating exceeds conductor ampacity"
Cause: Next standard OCPD size larger than conductor ampacity
Impact: The proposal is blocked unless the NEC 240.4(B) next-size-up conditions are satisfied
Solution: Increase conductor size or reduce the load/device constraint; auto-sizing does not hide the conflict by selecting a device below the required load current

Fuse class mismatch:

Warning: "Fuse class may not provide adequate protection"
Cause: Using Class J fuse where Class RK1 or CC recommended
Solution: Verify fuse class appropriate for application

Breaker interrupting capacity:

Warning: "Verify AIC rating adequate for fault current"
Cause: Sizing doesn't check short-circuit level
Impact: Breaker may fail to interrupt fault safely
Solution: Run short-circuit analysis and verify AIC ≥ fault current

Resolving sizing issues

For errors:

Note the specific error message.
Identify the component with issue (highlighted in editor).
Open component properties panel.
Fill in missing data or correct invalid values.
Try sizing again.

For warnings:

Read warning message carefully.
Determine if issue is acceptable for your application.
If acceptable: Document reason for deviation in project notes.
If not acceptable: Adjust component properties or use custom values.

Custom overrides

When warnings are acceptable:

Engineering judgment applied
Specific application knowledge
Equipment manufacturer requirements
Local code amendments

Documenting overrides:

Note warning in project documentation.
Explain reason for accepting.
Get PE review and stamp.
Include in calculation report.

When not to override:

Code violation (errors, not warnings)
Safety concern
Without engineering review
Customer requirements prohibit

NEC rule violations

Code violation indicators:

Shown as errors, not warnings
Prevent sizing completion
Must be addressed

Common violations:

Conductor below minimum size (#14 for branch circuit)
OCPD exceeds the applicable device-specific motor limit
Voltage rating mismatch
Termination temperature exceeded

Resolution:

Cannot override code violations
Must fix component data or system configuration
Contact support if you believe rule misapplied

Sizing result validation

After sizing completes:

Review sizing results panel
Check for any warnings
Verify sizes are reasonable
Compare to hand calculations if critical

Red flags requiring review:

Conductor much larger than expected
OCPD very high relative to load
Excessive voltage drop
Parallel conductors when not expected

Custom reference tables

Overriding NEC tables:

Use organization or user reference tables
Implement local amendments
Review the custom-data provenance recorded in sizing evidence

Custom overrides do not provide a CEC or IEC rules implementation and cannot change the project's selected code profile.

Warning changes:

Custom tables may eliminate warnings
Or create new warnings
Verify custom table correctness

See Customizing tables.

When to contact support

Contact support if:

Error message unclear
Sizing calculation hangs or crashes
Results appear incorrect despite valid data
Code rule seems misapplied

Use the feedback button (bug icon, bottom right of the editor) to send a report. It attaches the current page's diagnostics and, when available, a project export.

Include in the report:

Expected vs actual results
NEC article you believe applies

Cable sizing - NEC ampacity calculation details
OCPD sizing - Protection device sizing rules
Customizing tables - Override NEC values
Debug panel - Data inspection