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The Electrical Power Service Entrance (ESE) is installed specifically to bring electrical power into the facility from an outside source.
- Electrical power utility service drop
- Solar power panels
- Wind-powered generator
- Gasoline-powered generator
There can be only one ESE at a facility, but special exceptions have been made for additional ESEs to power fire safety equipment and fire fighting at large facilities. Ideally, multiple ESEs at any one facility should share the same GES and be bonded together through one or more ISBPs.
- Grounding Electrode Conductor (GEC).
- Water Main.
- Ground Rod.
- Main Bonding Jumper. This jumper brings three separate conductors together in the ESE at a single point designed for high ampacity and low resistance:
- Equipment grounding conductor from the facility interior.
- Isolated neutral conductor from the facility interior.
- Service drop neutral conductor from the facility exterior.
The ESE shares some traits with ISBPs that make it tempting for people to interpret the two as one and the same. However, it is inappropriate to describe the ESE as an ISBP because of one important difference -- the presence of a bonding connection between isolated neutral and ground at the supply side of the ESE.
The ESE cannot handle all incoming services because it is sized for electrical power service. There is no room for bonding all the systems of nonelectrical services. But, the ideal ISBP is constructed just for this purpose, and should have plenty of room.
Anyway, other incoming services are hardly obligated to use the ESE as they pass into the facility. This widens the insulation gap and offers new in-routes for current flow that bypass the ESE entirely. It is this dangerous problem that the ideal ISBP is supposed to solve. The balanced current through the ESE is never the same as the current coming in from the other services. Outdoor or indoor ISBPs easily handle all incoming services with independent grounding systems.
There is a National Electric Code requirement to separate the enclosures for adjacent services wiring, whether electrical or not. This complicates and rules out the use of the ESE for sponsoring many services. Thus, the ideal ISBP can never include the ESE, and the ESE can never contain an ISBP suite. The ESE therefore stands alone.
Circuit branches extend into the interior of the facility from the ESE and from sub-panels, which are all grounded back to the ESE. This is "supposed" to happen, but when evaluating a facility, do not assume that it "has" happened. See Missing Ground.
The ESE has only one GEC (or two paralleled for high ampacity) routed to ground at the GES. The GEC may serve a multi-point GES; it forces all current to balance before arriving inside the ESE.
The ESE takes current from the GEC and from the electrical service drop neutral conductor, and combines them through bonding. A special bonding jumper performs this function. It is called the main bonding jumper, and is considered to be a part of the line, or supply side of the ESE.
This main bonding jumper is also the sole connection to ground for the isolated neutral conductor, which crosses over from the load side of the ESE into the supply side of the ESE. See The Isolated Neutral.
Summary
Grounding connections between the electrical supply and the served facility are to be permitted only through the ESE and an outdoor ISBP, which prevents most hazards. The ESE alone is not an ISBP.
Electrical grounding and bonding are critical at the ESE, and the greatest available ampacity between the GES and ESE via the GEC is preferred.
