The last section of Article 250 Part III — and the one that finishes the on-disk Part III build. The previous articles picked the electrodes (250.50/250.52/250.53), sized the GEC (250.66 table + caps), and ran it (250.64). 250.68 said where the GEC lands on the electrode. 250.70 says how it physically lands: exothermic welding, listed lugs, listed pressure connectors, listed clamps, or other listed means — never solder — plus the ground-clamp listing rules, the one-conductor-per-clamp limit, and (in the 2017 edition) a four-methods hardware list that the 2023 reorganization removed.
Part III (Grounding Electrode Systems) is a sequence, and 250.70 is the last step. The prior articles each own one link in the chain, and 250.70 closes it:
Two adjacent sections that 250.70 leans on and that do not yet have their own page: 250.8 (Connection of Grounding and Bonding Equipment — the general permitted-methods list for EGCs, GECs, and bonding jumpers) and 250.10 (Protection of Ground Clamps and Fittings). Both are quoted below; 250.8 is where the "what counts as a listed connection" vocabulary comes from, and 250.10 is the physical-damage protection rule for the clamps 250.70 requires.
250.70 is electrode-specific. The general connection rules live in 250.8, and 250.70's clamps are the ones 250.10 protects. Both are word-identical 2017 → 2023 (verified against the on-disk 2023 CSV).
250.70 is one of the few Part III sections that genuinely changed structure between editions. The story is a 2023 reorganization — and it's a removal, not an addition.
The 2020 text of 250.70 is word-identical to 2017 — same single flat paragraph, same "where used on pipe, rod, or other buried electrodes" phrasing, same four-methods list (1)–(4). Source: ELR sectionID 1005.0 "2020 Code Language" (fetched 2026-09-15). No 2017→2020 change to record.
Per the 2023 NEC change summary (Mike Holt 2023 Code Change Summaries, Article 250): "250.70 … This section was reorganized into two first level subdivisions and editorially revised for clarity. An Informational Note providing helpful information was also added." Concretely, the on-disk 2023 text (2023 NEC CSV, rows 250.70(A)/250.70(B), cross-checked against the ELR 2023 "Code Language" block) shows exactly what that means:
What did NOT change: the (A) opening — "exothermic welding, listed lugs, listed pressure connectors, listed clamps, or other listed means" — is word-identical 2017→2023, as is the no-solder sentence and the one-conductor-per-clamp sentence. So the core rule (the methods + the no-solder + the clamp listing + the one-conductor limit) is stable across all three editions; only the enumerated hardware list and the subdivision structure moved.
250.70 is about the method of connection, not a size — so the "numbers" here are the GEC sizes 250.70 is landing, computed by the shipped cores (Table 250.66 + the caps), paired with the 250.70 connection that applies to each electrode type. Every ampacity / cmil / pick is from the real cores under node (compute_art48.js → art48_numbers.json); zero hand math.
| Item | Value (core) |
|---|---|
| Service | 200 A (75 °C column, 110.14(C)(1)(b) >100 A) |
| Required ampacity (125% × 200 A, 230.42(A)(1)) | 250 A |
| Ungrounded pick (310.16 @ 75 °C) | pickConductor31016(250, cu, 75) → 250 kcmil Cu (255 A; 250,000 cmil) |
| Table 250.66 row (250,000 cmil → "Over 3/0 through 350") | table GEC = 2 AWG Cu |
| Electrode: driven rod only (250.52(A)(5)); GEC does not extend on | 250.66(A) applies |
| GEC | 6 AWG Cu — cap (A) shrinks 2 AWG → 6 AWG (250.66(A)) |
| 250.70 connection | 2017 (2) listed bolted clamp of cast bronze or brass / plain or malleable iron, listed for the electrode + GEC materials and for direct soil burial → 2023 (A) "listed clamps" with the same soil-burial listing |
A buried rod is exactly the case where the 2017 "shall also be listed for direct soil burial" clause bites: the clamp is buried with the rod, so its listing must cover direct soil burial — not just the two metal materials it clamps.
| Item | Value (core) |
|---|---|
| Service | 100 A (60 °C column, 110.14(C)(1)(a) ≤100 A) |
| Required ampacity (125% × 100 A, 230.42(A)(1)) | 125 A |
| Ungrounded pick (310.16 @ 60 °C) | pickConductor31016(125, cu, 60) → 1/0 Cu (125 A; 105,600 cmil) |
| Table 250.66 row (105,600 cmil → "1 AWG or 1/0") | table GEC = 6 AWG Cu |
| Electrode: water pipe (250.52(A)(1)); no cap — table governs | no 250.66 cap |
| GEC | 6 AWG Cu — the table size (water pipe has no cap) |
| 250.70 connection | 2017 (1) "a pipe fitting, pipe plug, or other approved device screwed into a pipe or pipe fitting" → 2023 (A) listed lugs / listed pressure connectors / other listed means (the 2017 (1) pipe-plug method is no longer enumerated after the 2023 reorganization, but is still a permitted listed means) |
The water-pipe electrode is the clearest demonstration of the 2023 removal: the 2017 code named the pipe plug by name in 250.70(1); the 2023 code dropped that line, and the same pipe plug now fits under the (A) General "listed lugs / listed pressure connectors / other listed means" umbrella. Same hardware, different citation.
| Item | Value (core) |
|---|---|
| Service | 1000 A on two parallel sets (75 °C column) |
| Per-set required ampacity (125% × 500 A per set) | 625 A per set |
| Per-set ungrounded pick (310.16 @ 75 °C) | pickConductor31016(625, cu, 75) → 1500 kcmil Cu (625 A; 1,500,000 cmil per set) |
| Note 1 equivalent area (largest sum of corresponding conductor areas) | 2 × 1,500,000 = 3,000,000 cmil |
| Table 250.66 row (3,000,000 cmil → "Over 1100") | table GEC = 3/0 Cu — the CAPPED row |
| Electrode: ground ring only (250.52(A)(4)), 2 AWG Cu ring; GEC does not extend on | 250.66(C) applies |
| GEC | 2 AWG Cu — cap (C): need not be larger than the ring conductor |
| 250.70 connection | (A) General: a listed clamp / exothermic welding / listed lug to the 2 AWG Cu ring — the ring is a buried conductor, so any clamp is listed for direct soil burial / concrete encasement |
A ground ring is a continuous buried copper loop, so the 250.70 clamp-listing rule (direct soil burial / concrete encasement) is the relevant listing. Exothermic welding is a common way to tie the GEC to the ring — and it is explicitly in (A) General across all three editions.
| Item | Value (core) |
|---|---|
| Service | 500 A (75 °C column, 110.14(C)(1)(b) >100 A) |
| Required ampacity (125% × 500 A, 230.42(A)(1)) | 625 A |
| Ungrounded pick (310.16 @ 75 °C) | pickConductor31016(625, cu, 75) → 1500 kcmil Cu (625 A; 1,500,000 cmil) |
| Table 250.66 row (1,500,000 cmil → "Over 1100") | table GEC = 3/0 Cu |
| Electrode: concrete-encased (Ufer) only (250.52(A)(3)); rebar stubbed up per 250.68(C)(3); GEC does not extend on | 250.66(B) applies |
| GEC | 4 AWG Cu — cap (B) shrinks 3/0 → 4 AWG (250.66(B)) |
| 250.70 connection | (A) General: exothermic welding, listed lugs, listed pressure connectors, listed clamps, or other listed means — the rebar stub-up is a listed clamp / "other listed means"; solder is NOT permitted (250.70(A)) |
The Ufer stub-up is the textbook case for exothermic welding: you're bonding a 4 AWG GEC to a chunk of rebar, and welding is the cleanest "effective grounding path" (250.68(B)) you can make. Note the 2023 Informational Note's payoff here — a Ufer is concrete-encased, and the Note says a clamp identified for direct burial is also suitable for concrete encasement, so one listing covers the buried and concrete-encased cases.
Both 250.8(B) and 250.70 ban connections that depend solely on solder, and both have carried that ban across all three editions. The reason is practical: a solder joint at an electrode is a ground-fault-current path, not a normal current path. On a fault, the heat of the fault current can melt a eutectic joint exactly when you need the path to hold. Exothermic welding (a metallurgical bond, not a filler-metal joint), listed lugs, and listed pressure connectors survive that event; a solder fillet is a gamble. This is why 250.70's opening leads with "exothermic welding" and the 2023 (B) Informational Note exists to tell you a direct-burial-listed clamp also covers concrete — the code is telling you which listed means actually hold up in the ground.
Open the free PanelWright calculator — size the panel, the service, the neutral, the derating, and the voltage drop in your browserFree, in-browser, zero tracking. Data never leaves your browser. Design aid only — verify against the adopted NEC edition.
2026 edition (out of scope, flagged honestly): the only 2026 renumber confirmed by on-disk sources is Article 220 → 120. No on-disk source confirms the Article 250 section numbers moved, so this page assumes 250.70 numbering is stable across 2017–2023 and cites it as-is; verify section numbers against the NEC edition adopted in your jurisdiction.
Section text. Verbatim NEC 2017 (official NFPA text on disk, nec2017_full.txt): 250.70 (the single flat paragraph + the four-methods list (1)–(4)), 250.8 (A)/(B), and 250.10. OCR line-wrap reflow normalized; the 2017 scan's "conduc-tors" hyphen split at a line break is rejoined to "conductors" (line-wrap artifact, disclosed). No other wording altered.
Edition history. 2020 — ELR sectionID 1005.0 "2020 Code Language" (fetched 2026-09-15): word-identical to 2017. 2023 — on-disk 2023 CSV (rows 250.70(A)/250.70(B)), cross-checked against ELR sectionID 1607 "2023 Code Language" and the Mike Holt 2023 Code Change Summaries (Article 250, p.17: "reorganized into two first level subdivisions and editorially revised for clarity. An Informational Note … was also added"). The 2023 deltas are all four verified: (A)+(B) structure, the four-methods list removed, "where"→"if" editorial, and the new (B) Informational Note. The (A) opening + no-solder + one-conductor sentences are word-identical 2017→2023.
250.8 / 250.10. Quoted verbatim from the 2017 on-disk text; the 2023 CSV rows 250.8(A)/(B) and 250.10 are word-identical (verified cell-for-cell).
Worked numbers. Every ampacity / cmil / conductor pick computed by the shipped cores under node (compute_art48.js → art48_numbers.json): service sizing at 125% continuous (230.42(A)(1)) in the 110.14(C)(1) column (60 °C ≤100 A per (C)(1)(a); 75 °C >100 A per (C)(1)(b)); pickConductor31016 for the ungrounded pick; ch9Row/CH9_T8 for cmil; Table 250.66 rows + the three caps applied by the cap clauses. Zero hand math; the test suite re-runs the picks and asserts they match the page. The 2017 four-methods-list presence (pipe plug / bolted clamp / strap / equally substantial) and the "where" phrasing are asserted by the same script reading the on-disk 2017 text, so the removal claim is machine-checked, not from memory.
Source boundaries (stated, not asserted): the 2023 four-methods-list removal is established by the on-disk 2023 CSV (which prints only (A) General + (B)) + the Mike Holt 2023 change summary; a single on-disk 2020 full-code scan ending before Article 250 means the 2017→2020 word-identity rests on the ELR 1005.0 record (not a full on-disk 2020 code body). The ELR 2023 "Code Language" block for 250.70 previews (A) General only (its (B) + Informational Note are confirmed by the on-disk 2023 CSV, not by a second independent 2023 full-text source) — the (B) text therefore rests on the 2023 CSV + the change summary.
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