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:

"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 to generate detailed sizing results

"Sizing details are stale. Re-size to refresh.":

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

Accepted value changed but details still show old calculation:

Meaning: Cable, transformer, and protection-device suggestions write the reviewed component value before they refresh the

stored calculation card

What to do: Use Re-size on that component when you need the detailed card to match the accepted value

Bus amperage suggestions are the exception: accepting them refreshes the bus sizing details immediately.

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

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: Calculated value falls between standard sizes
Impact: Slightly oversized protection
Solution: Normal per NEC 240.4(B); verify acceptable

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: Increase conductor size 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:

Warning: "Auto-parallel: X runs of [size] selected (max single conductor: [threshold] kcmil). Per NEC 310.4."
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
Solution: Informational warning. Review the selected configuration. 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:

Warning: "OCPD rating exceeds conductor ampacity"
Cause: Next standard OCPD size larger than conductor ampacity
Impact: Conductor may not be protected
Solution: Increase conductor size to match OCPD or use next size down OCPD

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 code maximum (e.g., motor >250% FLC)
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
Apply alternative code book (CEC, IEC)
Implement local amendments

Warning changes:

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

See Customizing tables.

Debug export for sizing issues

Export sizing debug data:

Run sizing calculation.
Open debug panel.
Click Export Sizing Debug.
Review debug-exports/sizing-debug-[timestamp].md.

Debug file includes:

All component properties used in sizing
Applied derating factors
NEC table lookups
Calculation steps
Final results and warnings

Use for:

Troubleshooting unexpected results
Support tickets
Verifying calculations
Documentation

Preventing sizing issues

Before running sizing:

Complete all component required properties
Use realistic voltage levels (standard values)
Verify load powers are reasonable
Check cable installation types match actual

Good data hygiene:

Use component defaults appropriately
Validate data before sizing
Review sizing results critically
Don't blindly accept warnings

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

Include in support request:

Sizing debug export
Component properties (copy JSON from debug panel)
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