8.2 Service Disconnects, the 2020 Rule Change, SPDs and Service GFPE

Location of the Service Disconnect — 230.70

230.70(A)(1) Readily Accessible Location. The service disconnecting means shall 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 Code does not define "nearest the point of entrance" numerically. Local practice and AHJ interpretation typically limit unfused service conductors inside a building to a few feet. The reason is direct: service-entrance conductors have no overcurrent protection ahead of them, so a fault along their length inside a building burns until the utility transformer fuse operates or the conductors clear themselves.

230.70(A)(2) Bathrooms. Service disconnecting means shall not be installed in bathrooms.

230.70(A)(3) Remote Control. Where a remote-control device is used to actuate the service disconnecting means, the service disconnecting means shall be located in accordance with 230.70(A)(1).

230.70(B) Marking. Each service disconnect shall be permanently marked to identify it as a service disconnect.

230.70(C) Suitable for Use. Each service disconnecting means shall be suitable for the prevailing conditions. Service equipment installed in hazardous (classified) locations shall comply with the requirements of Articles 500 through 517.

The 2020 Change to 230.71

Through the 2017 edition, the service disconnecting means could consist of up to six switches or circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard — the familiar "six-handle rule." A six-space main-lug panel with six breakers and no main was a compliant service.

The 2020 edition rewrote the section:

230.71(A) General. The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception No. 1, 3, 4, or 5, shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard or in switchgear. There shall be no more than six sets of disconnects per service grouped in any one location. Each service disconnecting means shall be permanently marked to identify it as a service disconnect.

... For the purpose of this section, disconnecting means used solely for power monitoring equipment, transient voltage surge suppressors, the control circuit of the ground-fault protection system, or power-operable service disconnecting means, installed as part of the listed equipment, shall not be considered a service disconnecting means.

The important 2020 restructuring is that two to six service disconnecting means are permitted only where each is in its own enclosure or compartment. The permitted arrangements are:

1. Separate enclosures with a main service disconnecting means in each enclosure;
2. Panelboards with a main service disconnecting means in each panelboard enclosure;
3. Switchboard(s) where there is only one common busbar;
4. Service disconnects in switchgear or metering centers where each disconnect is located in a separate compartment.

What is no longer permitted is six branch-type breakers in a single main-lug panelboard acting as the service disconnecting means. The safety rationale is straightforward: with six handles in one enclosure, an electrician who opens all six still faces an energized bus, and there is no way to de-energize the enclosure from within it.

Because the wording and subsection lettering of 230.71 differ noticeably between the 2017 and 2020 editions, this is one to read directly out of the 2020 book on exam day.

Emergency Disconnects for Dwellings — 230.85

New in the 2020 edition and heavily tested:

For one- and two-family dwelling units, all service conductors shall terminate in disconnecting means having a short-circuit current rating equal to or greater than the available fault current, installed in a readily accessible outdoor location. If more than one disconnect is provided, they shall be grouped. Each disconnect shall be marked as follows:

1. EMERGENCY DISCONNECT, SERVICE DISCONNECT
2. EMERGENCY DISCONNECT, METER DISCONNECT, NOT SERVICE EQUIPMENT
3. EMERGENCY DISCONNECT, NOT SERVICE EQUIPMENT

Markings shall comply with 110.21(B).

The purpose is fire-service access: first responders need to kill power from outside without entering the structure. This is a new outdoor disconnect requirement for dwellings, distinct from the service disconnect location rule in 230.70.

Surge Protection — 230.67

Also new in 2020:

• 230.67(A) Surge-Protective Device. All services supplying dwelling units shall be provided with a surge-protective device (SPD).
• 230.67(B) Location. The SPD shall be an integral part of the service equipment or shall be located immediately adjacent thereto. An exception permits the SPD to be located at the next level of distribution downstream toward the load where it is not located in the service equipment.
• 230.67(C) Type. The SPD shall be a Type 1 or Type 2 SPD.
• 230.67(D) Replacement. Where service equipment is replaced, all of the requirements of this section shall apply.

Each of the four subsections is exam material. The type requirement — Type 1 or Type 2, not Type 3 — is the most commonly missed.

Service Overcurrent Protection — Part VII

230.90(A) Ungrounded Conductor. Each ungrounded service conductor shall have overload protection. Such protection shall be provided by an overcurrent device in series with each ungrounded service conductor that has a rating or setting not higher than the allowable ampacity of the conductor.

There are exceptions. Exception No. 1 permits, for motor-starting currents, ratings that conform to 430.52, 430.62, and 430.63. Exception No. 2 permits the next higher standard rating where the conductor ampacity does not correspond to a standard rating, up to 800 amperes — the same logic as 240.4(B). Exception No. 3 covers two to six circuit breakers or sets of fuses as the overcurrent device, where the sum of the ratings may exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors.

Exception No. 3 is the reason a residential service with 200-ampere conductors may legally feed a panel whose breaker ratings sum to far more than 200 amperes: the calculated load is what must fit, not the sum of the breakers.

230.91 Location. The service overcurrent device shall be an integral part of the service disconnecting means or shall be located immediately adjacent thereto.

230.94 permits the service overcurrent device to be located on the supply side of the service disconnect in specified cases.

Ground-Fault Protection of Equipment — 230.95

Ground-fault protection of equipment shall be provided for solidly grounded wye electrical services of more than 150 volts to ground but not exceeding 1000 volts phase-to-phase for each service disconnect rated 1000 amperes or more.

230.95(A) Setting. The ground-fault protection system shall operate to cause the service disconnect to open all ungrounded conductors of the faulted circuit. The maximum setting of the ground-fault protection shall be 1200 amperes, and the maximum time delay shall be one second for ground-fault currents equal to or greater than 3000 amperes.

230.95(B) Fuses. If a switch and fuse combination is used, the fuses employed shall be capable of interrupting any current higher than the interrupting capacity of the switch during a time that the ground-fault protective system will not cause the switch to open.

230.95(C) Performance Testing. The ground-fault protection system shall be performance tested when first installed on site. This test shall be conducted in accordance with instructions provided with the equipment. A written record of this test shall be made and shall be available to the authority having jurisdiction.

The covered system is essentially 480Y/277 V at 1000 A or more. A 208Y/120 V service is only 120 volts to ground and is excluded no matter how large it is. An ungrounded or impedance-grounded system is not solidly grounded and is likewise excluded.

Exception: the ground-fault protection provisions of this section shall not apply to a service disconnect for a continuous industrial process where a non-orderly shutdown will introduce additional or increased hazards. Fire pumps are exempted by 695.6.

Do not confuse this with the parallel feeder rule in 215.10, which applies the same thresholds to feeder disconnects, or with 240.13, which applies them to building or structure disconnecting means.

Equipment Permitted on the Supply Side — 230.82

Only the following equipment shall be permitted to be connected to the supply side of the service disconnecting means:

1. Cable limiters or other current-limiting devices;
2. Meters and meter sockets nominally rated not in excess of 1000 volts, provided all metal housings and service enclosures are grounded;
3. Meter disconnect switches nominally rated not in excess of 1000 volts that have a short-circuit current rating equal to or greater than the available fault current;
4. Instrument transformers, impedance shunts, load management devices, arresters, and Type 1 SPDs;
5. Taps used only to supply load management devices, circuits for standby power, fire pump equipment, fire and sprinkler alarms, and load management devices;
6. Solar photovoltaic systems, fuel cell systems, wind electric systems, energy storage systems, or interconnected electric power production sources;
7. Control circuits for power-operable service disconnecting means, if suitable overcurrent protection and disconnecting means are provided;
8. Ground-fault protection systems or Type 2 SPDs, where installed as part of listed equipment, if suitable overcurrent protection and disconnecting means are provided;
9. Connections used only to supply listed communications equipment under the exclusive control of the serving electric utility, if suitable overcurrent protection and disconnecting means are provided;
10. Meter-mounted transfer switches nominally rated not in excess of 1000 volts that have a short-circuit current rating equal to or greater than the available fault current.

That list is closed. Anything not on it must be on the load side of the service disconnect.