Service Entrance Switchgear & Main Distribution

A commercial electrical service may follow a path such as:

Utility Source → Metering → Service Entrance Equipment → Main Distribution → Transformers / Panels / Equipment

The exact configuration depends on the project.

The service entrance may involve:

• Utility transformer

• Underground service conduits

• Metering equipment

• Service entrance switchgear

• Switchboard

• Main disconnect

• Distribution sections

• Main feeders

• Grounding and bonding

Every downstream electrical system depends on this infrastructure being installed correctly.

Service entrance switchgear can serve as the primary point of electrical protection and distribution for larger commercial buildings.

Depending on the engineered design, it may contain:

• Main breakers

• Feeder breakers

• Metering

• Distribution sections

• Protective devices

• Control equipment

The equipment configuration is selected around the building load, service voltage, available fault current, utility requirements, and engineered distribution design.

OTC installs the equipment according to the approved plans and manufacturer requirements.

Commercial switchboards may distribute power from the service entrance to:

• Transformers

• Distribution panels

• Mechanical equipment

• Tenant electrical systems

• Large equipment

• Exterior systems

• Additional buildings

The main distribution should reflect how power needs to move through the finished facility.

A well-planned system also makes future maintenance and expansion easier.

The main service should be based on the electrical requirements of the completed building.

Major loads may include:

• HVAC

• Lighting

• Commercial kitchens

• Warehouse equipment

• Manufacturing equipment

• Pumps

• Motors

• EV charging

• Tenant loads

• Exterior systems

• Future expansion

For new commercial services and major distribution systems, the service calculations and electrical design are performed by the project electrical engineer.

OTC works from that engineered design and coordinates the field installation required to bring the system online.

The utility is a major part of a new commercial electrical service.

Coordination may involve:

• Service voltage

• Service point

• Utility transformer

• Transformer location

• Metering requirements

• Underground conduit

• Utility pull sections

• Easements

• Equipment access

• Energization requirements

These items should be addressed early because utility requirements can affect the electrical room, site plan, underground routing, equipment procurement, and construction schedule.

Ground-up commercial projects often begin electrically before the building walls exist.

Service infrastructure may include:

• Utility conduits

• Service conduits

• Transformer pathways

• Pull boxes

• Equipment pads

• Grounding infrastructure

• Large parallel conduit banks

This work needs to be coordinated before concrete, paving, and site improvements make changes difficult.

OTC plans underground routing around both the electrical design and the physical site conditions.

Larger commercial services can require substantial electrical pathways.

That may include:

• Multiple parallel conduits

• Large conductors

• Parallel feeder sets

• Long underground runs

• Large pull boxes

• Multiple distribution sections

These installations require planning for:

• Pull lengths

• Conduit bends

• Equipment entry

• Conductor installation

• Future access

A poorly planned pathway can add significant material and labor cost to an otherwise straightforward distribution system.

Commercial metering requirements can vary significantly between projects and utility providers.

The electrical service may involve:

• Utility metering

• CT metering

• Meter sections

• Multiple tenant meters

• Main building metering

OTC coordinates the physical installation around the approved utility and engineered requirements.

Metering should be resolved early so the service equipment is ordered in the correct configuration.

The main service voltage is not always the voltage used by every load in the building.

For example, a facility may receive and distribute power at 480Y/277V while using transformers to provide 208Y/120V for other building loads.

A common distribution path may be:

Service Entrance Switchgear → 480V Distribution → Transformer → 208Y/120V Panel → Branch Circuits

OTC coordinates the switchgear, transformers, feeders, and downstream panels as one complete system.

Large service equipment requires significant physical space.

Electrical-room planning needs to consider:

• Equipment dimensions

• Working clearances

• Equipment doors

• Conduit entry

• Feeder routing

• Transformer locations

• Future maintenance

• Equipment replacement access

The electrical room should be coordinated before the building layout becomes fixed.

Trying to fit large switchgear into a room that was designed too small creates problems that affect the entire project.

Service entrance switchgear is often one of the most schedule-sensitive materials on a commercial project.

Major electrical gear may be built specifically for the project and can have substantial manufacturing lead times.

Depending on the equipment and market conditions, lead times can extend for many months, and highly customized equipment can sometimes approach or exceed a year.

That makes early:

• Engineering

• Equipment selection

• Submittals

• Approval

• Release for manufacture

critical to the construction schedule.

The electrical room can be finished and the building nearly complete, but permanent power still cannot be energized without the service equipment.

Major gear should be reviewed carefully before release.

Important considerations may include:

• Voltage

• Amperage

• Breaker configuration

• Service rating

• Fault-current rating

• Metering

• Physical dimensions

• Conduit entry

• Manufacturer

• Accessories

• Future sections or provisions

A mistake in major service equipment can be much more difficult to correct than a mistake on a small panelboard.

OTC coordinates procurement around the approved engineered design and project requirements.

When reasonable, the main distribution system should consider how the building may change.

Future requirements may include:

• Additional tenant loads

• New equipment

• Building expansion

• EV charging

• Additional HVAC

• Production growth

That may affect decisions involving:

• Distribution sections

• Breaker provisions

• Electrical-room space

• Conduit pathways

• Transformer capacity

The objective is not to unnecessarily oversize the service.

It is to avoid creating a new building with no practical path for future electrical growth.

The service entrance is also a critical part of the building's grounding and bonding system.

OTC installs the required grounding and bonding components according to the engineered design and applicable requirements.

Depending on the project, that may include:

• Grounding electrode system

• Grounding electrode conductors

• Service bonding

• Equipment grounding

• Transformer grounding

• Distribution grounding

These systems are coordinated as part of the overall electrical installation rather than added as an afterthought.

Before permanent power is placed into service, the installed equipment needs to be verified.

Depending on the project requirements, that may include:

• Visual inspection

• Connection verification

• Mechanical checks

• Insulation-resistance testing where appropriate

• Breaker testing where required

• Phase verification

• Voltage verification

• Control testing

• Equipment labeling

Specialized acceptance testing may also be performed by qualified testing agencies when required by the engineer, specifications, manufacturer, or AHJ.

OTC coordinates the installation and field requirements leading up to final energization.

A complete service entrance and main-distribution scope may include:

• Utility coordination

• Underground service conduit

• Transformer infrastructure

• Metering

• Service entrance equipment

• Switchgear

• Switchboards

• Main disconnects

• Distribution sections

• Transformers

• Main feeders

• Grounding and bonding

• Equipment testing

• Utility inspection coordination

• Final energization

OTC coordinates the electrical construction from the incoming utility infrastructure through the main distribution equipment serving the building.