3.2 Service Equipment, Disconnecting Means & Massachusetts Dwelling Rules
Key Takeaways
- Service disconnects must be readily accessible and located outside or inside nearest the point of entrance of service conductors; they are not permitted in bathrooms.
- The service disconnect rating is based on the calculated load and the applicable minimums; a one-family dwelling service disconnect is generally at least 100 amperes, 3-wire, while other installations generally have a 60-ampere minimum unless a specific smaller-load rule applies.
- Where the six-disconnect rule is used, the permitted disconnects must be grouped and installed in separate enclosures, separate vertical sections, or other arrangements allowed by the governing NEC edition.
- Massachusetts modified the dwelling exterior-disconnect rules in both the 2023 and 2026 code cycles, so candidates must answer from the edition named in the examination materials.
- The current 2026 Massachusetts amendment locates the dwelling requirement in 230.70(A)(1) and contains a remote-control option for certain underground-supplied dwellings.
3.2 Service Equipment, Disconnecting Means & Massachusetts Dwelling Rules
Quick Answer: Size a service disconnect for the calculated load and applicable NEC minimum, place it in a readily accessible location outside or inside nearest the service-conductor entrance, and never place it in a bathroom. The NEC permits up to six service disconnects only when the applicable grouping and enclosure rules are satisfied. For dwelling exterior disconnection, use the exact code edition named in the PSI materials: the 2023 Massachusetts amendment modified NEC 230.85, while the current 2026 Massachusetts amendment places its rule in 230.70(A)(1).
1. Location and Accessibility
The service disconnecting means is the point at which the premises wiring can be disconnected from the service conductors. NEC 230.70 requires it to be readily accessible and located either outside or inside nearest the point where service conductors enter the building. “Nearest” is not a universal number of feet. The authority having jurisdiction evaluates the actual route, building construction, and local amendment.
Do not route unfused service conductors deep into a building merely because a convenient panel location exists. Common solutions are an exterior service disconnect, a disconnect immediately inside the point of entrance, or service conductors encased in the construction method the governing rule recognizes as outside the building.
The disconnect cannot be installed in a bathroom. It must also satisfy working-space, illumination, guarding, and dedicated-space provisions that apply to the equipment. Readily accessible means the operator does not need a portable ladder, tools, or removal of obstacles.
2. Number and Grouping of Disconnects
The traditional “rule of six” does not mean six breakers anywhere in a building. NEC 230.71 permits not more than six service disconnects for each service or for each set of service-entrance conductors permitted by the Code. NEC 230.72 requires grouping at one location, subject to its stated exceptions.
Modern editions restrict how multiple disconnects share equipment. The 2023 NEC generally requires each service disconnect in a separate enclosure or separate compartment of switchgear or switchboards, or in another expressly permitted arrangement. This avoids exposing a worker to energized service bus while servicing a neighboring disconnect. When an exam gives a specific edition, check the exact list rather than applying an older “six handles in one panelboard” memory rule.
A disconnect must plainly indicate open or closed position and be suitable for use as service equipment where that identification is required. The service equipment must be listed, have a short-circuit current rating adequate for the available fault current, and be installed so the overcurrent device interrupting rating is not exceeded.
3. Rating the Service Disconnect
NEC 230.79 ties the disconnect rating to the load and establishes minimum ratings. Key exam anchors include:
- for a one-family dwelling, the service disconnect is normally at least 100 amperes, 3-wire;
- for installations consisting of two 2-wire branch circuits, the rule provides a 30-ampere minimum;
- for a one-family dwelling with a limited calculated load under the specific provision, and for certain other installations, additional stated minimums apply;
- in the general case not covered by a smaller specific provision, the minimum is 60 amperes.
Do not select a disconnect from the minimum alone. If the Article 220 calculation is 137 amperes, a 100-ampere dwelling minimum does not make a 100-ampere service acceptable. Select a permitted standard rating at least large enough for the calculated load and coordinate conductors, service equipment, and overcurrent protection.
For multiple-occupancy buildings, occupants generally need access to their disconnects unless building management and electrical maintenance arrangements satisfy an exception. Service equipment must also be marked to identify the load served when needed to avoid confusion.
4. Grounded Conductor and Bonding at Service Equipment
At service equipment, the grounded service conductor is bonded to the service enclosure through the main bonding jumper. The grounding electrode conductor connects the grounded service conductor or permitted service point to the grounding electrode system. On the load side of the service disconnect, grounded conductors and equipment grounding conductors are kept separate except where another Code rule specifically establishes a separately derived system or other connection.
This service-versus-feeder boundary matters in questions showing a meter-main outside and a distribution panel inside. Once the exterior disconnect is service equipment, the interior panel is supplied as a feeder: run an equipment grounding conductor with the feeder, isolate the neutral bar, bond the equipment grounding bar to the enclosure, and do not install a second neutral-to-case bond.
5. Massachusetts Dwelling Exterior-Disconnect Changes
The unamended 2023 NEC text in 230.85 addresses an emergency disconnect at one- and two-family dwellings. Massachusetts did not simply adopt that sentence unchanged.
Under the 2023 Massachusetts amendment, 230.85 applied to new one- and two-family dwellings, new double-occupancy buildings with at least one dwelling unit, and certain two-family or double-occupancy buildings newly created by subdividing an existing one-family dwelling. It also applied when a one- or two-family service was entirely replaced or increased in ampere capacity. Replacement limited to listed components—meter sockets, service-entrance conductors, related raceways and fittings, or the main overcurrent device—was excluded. The amendment also allowed remote control of an indoor service disconnect for certain underground supplies with the specified exterior marking and raceway-protected control wiring.
The current 2026 Massachusetts Electrical Code, effective April 24, 2026, reorganizes the requirement under 230.70(A)(1). It calls for the service disconnect for the described one- and two-family/double-occupancy applications to be in a readily accessible outdoor location. Its underground-supply exception permits remote control of an indoor service disconnect from a readily accessible outdoor location and specifies the marking EMERGENCY ELECTRICAL DISCONNECT AND NOT SERVICE EQUIPMENT with control wiring in a raceway. A separate exception addresses limited component replacement.
The exam bulletin says new items may be added seven months after a newly enforced code, and the Board's May 18, 2026 minutes state that exam changes should be reflected by November. Therefore, do not answer a transition-period question from memory. Check the code edition printed in the question or authorization.
6. Labels Are Exact-Code Questions
Do not invent color, letter-height, or material requirements. Use the wording and durability requirements in the tested edition, plus any equipment listing and local utility specification. Utility meter height, hot-sequence or cold-sequence arrangements, and meter-socket details are utility requirements, not universal text of NEC 230.85 or 230.70.
An exam-ready method is:
- identify the tested code edition;
- decide whether the project is new construction, full service replacement, capacity increase, or limited repair;
- apply the Massachusetts parent language and exceptions;
- determine whether the exterior device is service equipment or only remote control;
- select the exact marking from the governing text.
Where must a service disconnect generally be located?
Under the 2023 Massachusetts amendment, which project generally triggered the amended dwelling emergency-disconnect rule?
A calculated one-family dwelling load is 137 amperes. What controls selection of the service disconnect?