Understanding what a “Service” is when it comes to electrical applications is very important to determine what part of the code you need to run to for requirements.
The electrical code makes it clear that a service includes the conductors and equipment that connect the serving utility to the wiring system of the premises that is being served by this connection.
In the history of this term, the electrical code didn’t come right out and include the direct association with a utility. Then again, as you walk through the history of service applications, what we think of as a service today is arguably different than what it was many years ago. There were a few key times in history where changes were made either directly to the definition of this term or in related areas of the code that are quite significant and influenced the application. Through understanding those changes, you will help in your understanding of the service and applications around this equipment.
Let’s look at the history of this defined term and related terminology to better understand the electrical service.
1923 edition
We’ll start our journey in the 1923 edition of the electrical code. You’ll note that in this language, the defined term addressed only the physical nature of the equipment and not the power flow from one location to another. the definition in this edition of the code reads as follows:
That portion of the supply conductors which extends from the street main to the service switch of the building supplied.
This language only addressed the equipment which extend from the street main to the service switch and does not address a flow of power from one location to another.
1940 edition
The language found in the 1940 edition of the electrical code is different than the 1923 edition bringing more words to the table. This definition is very inclusive of many different possible sources and speaks to the direction of the flow of energy.
A service is the conductors and equipment for delivering electric energy from the secondary distribution or street main, or from a distribution feeder, or from the transformer, to the wiring system of the premises served.
As you can see in this definition, the language now included the direction of power flow. the terms feeder and transformer are used but one could argue that this equipment is still the utility as in 1940 alternative energy solutions like PV, Wind, and energy storage did not have a market presence as they do today. is from the street main, distribution feeder, or transformer to the wiring system of the premises served.
1947 – 1990 electrical code
Moving forward to the 1947 edition through the 1990 edition of the code, we see a simplified and arguably a streamlined version of the definition. This definition would not change until the 1999 edition of the code. In this definition, the flow of energy is still present
The conductors and equipment for delivering energy from the electricity supply system to the wiring system of the premises served.
This definition uses the term “electricity supply system” which is not defined in the NEC. It appears to replace “secondary distribution or street main, or from a distribution feeder, or from the transformer” with “electricity supply system”. Not having a record of the substantiation for a change, we can only assume that the intent is to maintain the original intent but simplify and streamline the language. Keep in mind too that in the 1940’s the source of power was prominently from a utility.
1993 edition
The 1993 cycle played an important role in the future of the the defined term Service. This edition introduced changes that influenced a future change of the definition of service. It was during this edition of the electrical code that the term “Service Point” entered the electrical code. This term was added to the definition of premises wiring such that the definition for premises wiring read as:
Premises Wiring (System): That interior and exterior wiring, including power, lighting, control, and signal circuit wiring together with all of their associated hardware, fittings, and wiring devices, both permanently and temporarily installed, that extends from the service point of utility conductors or source of a separately derived system to the outlet(s). Such wiring does not include wiring internal to appliances, fixtures, motors, controllers, motor control centers, and similar equipment.
Service point was also added to section 230-10 Service Conductors. In 230-10, the revised language read as “The conductors from the service point to the service disconnecting means shall be considered service conductors.” Service point appears in 6 locations in the 1993 edition of the electrical code.
The definition of service for NEC 1993 did not change but the influence of the addition of “Service Point” will to be seen until later. the 1993 edition of the electrical code defines service as follows:
The conductors and equipment for delivering energy from the electricity supply system to the wiring system of the premises served.
1999 edition
The change during the 1999 cycle began the association of service with the utility through changing the language “from the electricity supply system” to “from the serving utility”. The submitter during the public comment phase of the electrical code when suggesting this change, noted the following:
“This comment correlates this definition with Panel actions on related definitions of service conductors and service equipment (Proposals 1-134, 1-135). Non-utility electric supply systems are normally separately derived systems and covered elsewhere. This comment incorporates the thinking in the affirmative comment on vote.”
The definition of service conductors had seen changes during the 1996 edition and 1999 edition. Prior to the 1996 edition, the 1993 edition included a definition of service conductors that read as follows:
The supply conductors that extend from the street main or from transformers to the service equipment of the premises supplied
During the 1996 edition, this definition was modified to include the term “service point” removing the language “from the street main or from transformers”. it also included “or other source of power” bringing in to this term the possibility that alternative energy power sources are now service conductors. The definition of service conductors as founding the 1996 edition of the electrical code reads as follows:
The conductors from the service point or other source of power to the service disconnect means.
During the 1999 edition, the debate revolved around the inclusion of “or other source of power” as a service conductor. Based on the language of the 1996 edition of the code, a conductor that originates from a generator and supplies a structure, even if there is no utility in the picture, are service conductors and not a feeder. The submitter noted that removal of the words “or other source of power” is necessary to avoid confusion. the definition of service conductors in the 1999 edition of the code reads as follows:
The conductors from the service point to the service disconnecting means.
The result of these debates and changes resulted in the definition of service as found in the 1999 code to read as follows:
The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.
This language would persist until the 2020 edition of the Code.
2020 edition
The 2020 edition of the electrical code introduced yet another significant change to the definition of service. This edition of the code modified the words “from the serving utility to the wiring system of the premises served” and changed it to “connecting the servicing utility to the wiring system of the premises served.” The debate at this point surrounded the interconnected systems on the line-side of the service disconnecting means. It was in this same cycle that a new term was introduced into Article 705. The term that caused confusion and some would argue conflict was the term “Power Source Output Circuit”. This term is defined as follows in the 2020 edition:
Power Source Output Circuit. The conductors between power production equipment and the service or distribution equipment.
This defined term left the electrical industry struggling with how to address the conductors that connect to the line-side of the service disconnect. The question in the minds of many was “Are these conductors service conductors or are they power source output conductors?” This distinction is critical because if you call them service conductors, then the disconnect is a service disconnect and that means grounding and bonding rules must be followed and much more.
The 2020 edition of the code defines service as follows:
The conductors and equipment connecting the serving utility to the wiring system of the premises served. (CMP-10)
The journey of interconnected systems when connecting to the line-side of the service disconnecting means formally began during this code cycle. Various sections of the electrical code began to adjust to address the conflicts created by new terms and new requirements for this area of the code.
2023 edition
The definition of Service as found in the 2023 edition did not see change from the language of the 2020 edition of the code. It reads as follow
The conductors and equipment connecting the serving utility to the wiring system of the premises served. (CMP-10)
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