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NEC Article 250.66 & Table 250.66Worked ExampleElectrical

Grounding Electrode Conductor (GEC) Sizing for 200A Service

Size the Grounding Electrode Conductor for a 200A residential service with 2/0 copper service conductors using NEC Table 250.66.

Direct Answer
4 AWG Copper GEC (6 AWG max for ground rods, 4 AWG for Ufer ground)

Calculated strictly in accordance with NEC Article 250.66 & Table 250.66.

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Given Scenario Parameters

wattage48000
voltage240
continuousNon-continuous

Interactive Calculator (Pre-filled)

Adjust inputs to evaluate variations of this NEC code scenario.

Interactive Electric Load Calculator

Pre-loaded with NEC 220.51 & 424.3(B) parameters

Nameplate wattage of the heating unit or load

Line-to-line or line-to-neutral

NEC 424.3(B) mandates that fixed electric space heating equipment branch circuits must be sized at 125% of the total load current.

Calculated OutputLive Recalculation
Base Running Current200 A48000W ÷ 240V
Required Ampacity (125%)200 A200A × 1
Minimum Circuit Breaker:200 Ampere
Recommended Conductor (75°C Cu):1 AWG Copper
Overcurrent Protection Rule:NEC 240.4 & 424.3(B)
Adjust wattage or voltage on the left to recalculate continuous service loads instantly.

Step-by-Step Solution

Formal engineering derivation citing applicable National Electrical Code articles.

Governing Code Equation
GEC Size = Lookup(Service Conductor Size in Table 250.66)
Citing NEC Article 250.66 & Table 250.66
1

Identify service entrance conductor gauge: 2/0 AWG Copper.

2

Consult NEC Table 250.66 under '2/0 or 3/0 AWG Copper'.

3

Read required GEC size: 4 AWG Copper (or 2 AWG Aluminum).

4

Special electrode exceptions: Ground rods require maximum 6 AWG copper (NEC 250.66(A)); concrete-encased electrodes require maximum 4 AWG copper (NEC 250.66(B)).

Conclusion: 4 AWG Copper GEC (6 AWG max for ground rods, 4 AWG for Ufer ground)
NEC Article 250.66 & Table 250.66