Service Disconnect Rules (NEC 230 Part VI)
Why this matters
A failed inspection on a service-disconnect placement issue costs the contractor a full re-trip, sometimes weeks of utility-coordination delay, and customer relationship damage that is hard to recover. The disconnect rules in NEC 230 Part VI changed materially in 2020 and again in 2023; a contractor whose mental model is the 2014 cycle is making decisions that no longer pass. The "six-throws rule" was eliminated. Emergency-disconnect requirements for one- and two-family dwellings are now mandatory. Knowing the current rules - especially the differences between dwelling and non-dwelling and between the 2020 and 2023 cycles - is what separates the inspector-passing install from the one that comes back with a red tag.
Where the disconnect goes
NEC 230.70(A)(1) requires service disconnects to be:
Installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors.
The key phrases:
- Readily accessible: no ladders, no tools, no doors with locks the customer cannot operate
- Outside the building: legal anywhere on the exterior, no proximity rule
- Inside, nearest the point of entrance: typically interpreted as within 5 to 10 feet of where the service conductors enter the building (specific limit varies by AHJ; some jurisdictions interpret "nearest" strictly)
The contractor's safest play: install outside whenever possible. An outside-mounted disconnect satisfies the rule without the "nearest the point of entrance" debate.
The 2020 emergency-disconnect rule for one- and two-family dwellings
NEC 2020 added 230.85: every one- and two-family dwelling shall have an emergency disconnect located outside, accessible to first responders.
The 2023 NEC retained and clarified this. Three permitted configurations:
- Service disconnect outside (the disconnect itself satisfies the rule)
- Service disconnect inside, with emergency disconnect outside (the emergency disconnect ahead of the service disconnect)
- Meter disconnect outside, with service disconnect inside (the meter combination ahead of inside service disconnect)
Marking required: "EMERGENCY DISCONNECT" (or similar specific language per 230.85). The intent is that a first responder arriving at the scene of a fire can de-energize the home from outside before entering.
This rule is among the most-missed in residential work. A 2020 or later home with no outside disconnect fails inspection.
The 2023 NEC retired the "six-throws" rule
Under NEC 2017 and earlier, a single service could feed up to six disconnects in one location ("six throws of the hand" rule). NEC 2020 and 2023 require a single main disconnect per service. The "two to six" service configuration is gone for new install (existing remains grandfathered).
Single service, single main disconnect, then distribution from the main. Multiple panelboards downstream is fine; multiple service disconnects ahead of the panels is no longer.
Exception: NEC 230.71(B) permits multiple disconnects if each is in a separate enclosure (so they cannot be simultaneously operated) with specific permanent identification.
Maximum number of disconnect throws
For a single service:
- New installation post-2020: one main disconnect
- Multi-tenant building (apartment, mixed-use): each tenant unit can have its own service disconnect, but the building has one service-entrance combination per service entering the building
For services with multiple service-entrance taps, each tap requires its own disconnect ahead of branch distribution.
Accessibility requirements
NEC 110.26 working space rules apply to service disconnects:
| Voltage | Working space depth (Condition 1) | Working space depth (Condition 2) | Working space depth (Condition 3) |
|---|---|---|---|
| 0 to 150 V | 3 ft | 3 ft | 3 ft |
| 151 to 600 V | 3 ft | 3 ft 6 in | 4 ft |
Condition 1: exposed live parts on one side, no other live parts on the other side
Condition 2: exposed live parts on one side, grounded parts on the other side
Condition 3: exposed live parts on both sides
Additionally:
- 6 ft 6 inch headroom minimum
- 30 inch width minimum (or width of equipment, whichever is greater)
- Dedicated equipment space above the disconnect (6 ft high, equipment-width) free of foreign systems
A service disconnect in a closet jammed full of household storage violates 110.26. A disconnect behind a furnace where the working space overlaps the furnace clearance violates. Document the access at inspection.
Identification of disconnects
NEC 230.66 requires each service disconnect to be marked indicating its purpose. Engraved phenolic plate, embossed metal tag, or other permanent marking. Sharpie on the cover is not compliant.
For multiple disconnects (legacy installs with the six-throw rule pre-2020), each disconnect must be marked with its specific function.
For multi-tenant buildings, the disconnect marking should identify the unit it serves ("Disconnect for Apt 3B").
Disconnect overcurrent rating
Per NEC 230.90, each ungrounded conductor must have overcurrent protection rated no greater than its ampacity. For service-entrance conductors:
| Service rating | Typical SE conductor | Typical OCPD |
|---|---|---|
| 100A residential | 4 AWG copper SE-U cable | 100A main breaker or 100A fused disconnect |
| 200A residential | 2/0 AWG copper SE-U or aluminum | 200A main breaker |
| 400A residential | 500 kcmil aluminum SE-U | 400A main breaker (typically in panelboard or fused disconnect) |
| Commercial 600A+ | Per design | Per design, often fused switch |
The OCPD must also satisfy the available fault current (AIC rating) per the utility-supplied figure.
Ground-fault protection (commercial)
NEC 230.95 requires ground-fault protection on services 1000A or greater at 150 to 1000V. The ground-fault sensor and relay are installed at the service-entrance equipment. Residential below 1000A is not covered by this rule.
For services that include it, the GFP must be tested by an independent firm at commissioning and annually thereafter per NEC 230.95(C).
Disconnect for one- and two-family dwellings: practical examples
Standard install: outside service disconnect
References
- NFPA 70 (NEC) 2023, Article 230, Part VI (Service Equipment Disconnecting Means).
- NFPA 70 (NEC) 2023, Section 230.66 (Marking).
- NFPA 70 (NEC) 2023, Section 230.70 (Disconnecting Means location and accessibility).
- NFPA 70 (NEC) 2023, Section 230.85 (Emergency Disconnects).
- NFPA 70 (NEC) 2023, Section 230.95 (Ground-Fault Protection of Equipment for Services).
- NFPA 70 (NEC) 2023, Article 110.26 (Spaces about Electrical Equipment).
- NFPA 70 (NEC) 2023, Article 225 (Outside Branch Circuits and Feeders).
- UL 67 (Panelboards) and UL 50 (Enclosures).
- Local jurisdiction amendments to NEC (varies; check with AHJ).
- Manuall internal: Electrical Service Entrance Meter Base, Electrical Service Panel Upgrade, Electrical Commercial Three-Phase Service Entrance.