Reference tables overview

Reference tables contain electrical data used by the sizing engine to calculate conductor ampacity, derating factors, and OCPD sizes according to NEC 2026.

What reference tables are

Reference tables store code-required data:

NEC ampacity tables (310.16, 310.17)
Temperature correction factors (310.15(B)(1))
Conductor adjustment factors (310.15(C)(1))
Motor full-load current tables (430.248, 430.250)
Standard OCPD sizes (240.6)
Motor conductor and protection multipliers (430.22, 430.52)

The sizing engine queries these tables during cable and OCPD sizing calculations.

NEC 2026 default tables

ekx includes NEC 2026 tables as system defaults:

Table Key	NEC Article	Content
nec_310_16_cu_60	310.16	Copper ampacity at 60°C
nec_310_16_cu_75	310.16	Copper ampacity at 75°C
nec_310_16_cu_90	310.16	Copper ampacity at 90°C
nec_310_16_al_60	310.16	Aluminum ampacity at 60°C
nec_310_16_al_75	310.16	Aluminum ampacity at 75°C
nec_310_16_al_90	310.16	Aluminum ampacity at 90°C
nec_310_15_b_1_ambient_correction	310.15(B)(1)	Temperature derating factors
nec_310_15_c_1_adjustment_factors	310.15(C)(1)	Bundling adjustment factors
nec_240_6_standard_ocpd_sizes	240.6	Standard breaker/fuse ratings
nec_430_248_motor_flc_1ph	430.248	Single-phase motor FLC
nec_430_250_motor_flc_3ph	430.250	Three-phase motor FLC
nec_430_22_motor_conductor_multiplier	430.22	Motor conductor sizing (1.25×)
nec_430_52_motor_ocpd_multipliers	430.52	Motor OCPD sizing by type

These tables cannot be modified at system level but can be overridden at org or user level.

Scope-based customization

Reference tables use the same hierarchy as component defaults:

System (built-in):

NEC 2026 tables
Cannot be modified
Base for all customization

Organization:

Company-wide table overrides
Alternative standards or local amendments
Applies to all org members

User:

Personal table customization
Testing alternative values
Applies only to you

Organization tables override system tables. User tables override both.

How tables are used in sizing

Cable sizing:

Lookup ambient temperature factor from nec_310_15_b_1_ambient_correction.
Lookup conductor adjustment factor from nec_310_15_c_1_adjustment_factors.
Calculate required base ampacity.
Lookup conductor size from nec_310_16_cu_XX based on material and termination temp.
Return selected conductor size and adjusted ampacity.

OCPD sizing:

Calculate required OCPD current (load × continuous factor).
Lookup next standard size from nec_240_6_standard_ocpd_sizes.
For motors, lookup FLC from nec_430_248 or nec_430_250.
Apply multiplier from nec_430_52_motor_ocpd_multipliers based on device type.
Return selected OCPD size.

Tables provide the code-mandated values for these calculations.

Table data format

Tables are stored as JSON with structure specific to each table:

Ampacity table example:

{
  "14": 20,
  "12": 25,
  "10": 35,
  "8": 50,
  ...
}

Motor FLC table example:

{
  "voltage": {
    "460": {
      "1": 1.1,
      "2": 2.1,
      "3": 3.0,
      ...
    }
  }
}

Multiplier table example:

{
  "multiplier": 1.25
}

Format varies by table type but all tables are queryable by the sizing engine.

When to customize tables

Use system tables when:

Designing to NEC 2026
Standard US projects
No special requirements

Customize organization tables when:

Company standards differ from NEC
Local code amendments apply
Alternative code book (CEC, IEC)
Internal design standards

Customize user tables when:

Testing alternative values
Research or comparison studies
Personal preference for calculations

Most users never need to customize tables - system defaults handle typical NEC 2026 projects.

Customizing tables - How to create custom reference tables
Cable sizing - How sizing uses ampacity tables
OCPD sizing - How sizing uses OCPD and motor tables