Industry — Commercial Facilities
Service entrance, tenant distribution and retrofits engineered for occupied buildings
Commercial buildings need distribution that meets code, meters tenants accurately and can be modified while the building stays open. Apex engineers service-entrance switchboards, distribution and metering for new construction, and plans retrofits of aging equipment in occupied buildings where an outage means lost rent and unhappy tenants.
Operating realities
What makes commercial facilities distribution its own discipline
Service-entrance ratings and utility coordination
The service switchboard has to match the utility's available fault current, metering requirements and service conductor arrangement, all of which vary by utility and by service size. Ground-fault protection on services 1,000 A and larger, surge protection and the location of the service disconnects are decided with the utility and the authority having jurisdiction. Getting the utility's fault current letter early avoids under-rated equipment.
Tenant metering and distribution changes
Tenant spaces change hands and change shape, so distribution has to accommodate new feeders, submetering and load additions without disturbing neighboring tenants. Metering accuracy and the ability to report consumption by tenant matter for billing and for energy programs. Spare breaker positions and a documented panel schedule save considerable trouble over the life of the building.
Retrofit and replacement in an occupied building
Replacing a 40-year-old switchboard in a building that stays open requires temporary power, phased cutovers, tight outage windows and coordination with tenants, the utility and the fire alarm and elevator contractors. Breaker retrofills and section-by-section replacement are options when the bus and enclosure are sound. The sequence of work is engineered as carefully as the equipment.
Standby power for life safety and business continuity
Egress lighting, fire pumps, elevators and smoke control rely on emergency power that must be separated from the normal system and transferred within the time the code requires. Tenants may also want optional standby power for their operations. Transfer switches, generator sizing and the separation of emergency and standby distribution follow from the load classification.
How Apex fits
LV, MV, automation and monitoring for commercial facilities
Low-voltage equipment
Service-entrance switchboards and tenant distribution
Apex engineers UL 891 service-entrance and distribution switchboards with utility metering sections, ground-fault protection where required and tenant metering, sized for the building's growth. Breaker retrofills and section replacements are engineered for existing lineups where the bus and enclosure justify keeping them.
Learn moreMedium-voltage equipment
Medium-voltage service for large properties
Large campuses, high-rise buildings and mixed-use developments that take service at 15 kV class use metal-enclosed fused load-interrupter switchgear or metal-clad switchgear feeding unit substations and vault transformers. The choice between them follows the owner's reliability needs, maintenance approach and budget.
Learn moreAutomation & controls
Transfer switches and generator control
Automatic transfer switches for emergency and optional standby loads, generator controls and any main-tie-main arrangement are engineered and documented against the sequence of operations the design engineer specifies. Interfaces to the building automation system report status without giving it control of protective functions.
Learn moreMonitoring & analytics
Tenant metering, demand and equipment condition
Tenant submeters, main metering and breaker status are collected into a building energy management or monitoring platform over Modbus TCP or BACnet gateways where applicable. Demand trends, power-quality events and breaker condition indicators help property engineers plan maintenance and answer tenant questions with data.
Learn moreTypical equipment
What a commercial facilities one-line usually contains
- 480 V UL 891 service-entrance switchboards, 1,600 A to 4,000 A, with utility metering sections
- Ground-fault protection on service disconnects 1,000 A and larger where required
- Tenant distribution switchboards and submetering
- 15 kV class metal-enclosed fused load-interrupter switchgear for large-property service
- Automatic transfer switches for emergency, legally required and optional standby loads
- Breaker retrofill and section replacement for aging switchboards
- Surge protective devices at the service entrance
- Building energy monitoring gateways (Modbus TCP, BACnet where applicable)
Codes and standards that commonly apply
Specifications govern
- Switchboards are typically listed to UL 891; where a project specifies low-voltage power switchgear, it is typically listed to UL 1558. The equipment class the design engineer specifies governs.
- Service equipment, ground-fault protection and working clearances commonly follow NEC Articles 230, 240 and 110 as adopted by the jurisdiction; emergency and standby systems commonly follow Articles 700, 701 and 702. The authority having jurisdiction and project specifications govern.
- Maintenance on existing equipment commonly follows NFPA 70E for electrical safety and NFPA 70B for maintenance programs; the owner's procedures govern how work is performed in an occupied building.
Questions we hear
Frequently asked
+Can our switchboard be replaced without shutting the building down?
Usually the work is phased: temporary power or a temporary service carries critical loads, sections are replaced or retrofilled in planned outage windows, and life safety systems are kept on a defined source throughout. The feasibility depends on the utility's ability to provide a temporary service, the condition of the existing bus and how the building's loads can be grouped. A survey and a written cutover plan come before any equipment order.
+When is a breaker retrofill preferable to a new switchboard?
When the existing bus, enclosure and cable terminations are in good condition and the short-circuit rating still exceeds the utility's available fault current. Retrofilling replaces the breakers and often adds electronic trip units and communications while keeping the structure and conduits in place, which shortens outages. If the bus is degraded or ratings are exceeded, replacement is the sound choice.
+What does tenant metering require from the switchboard?
Metering-grade current transformers and voltage connections at each tenant feeder, meters with the accuracy class the billing program requires, and a communications path to the energy management platform. Where revenue billing is involved, local utility and weights-and-measures rules on meter accuracy and certification apply, and the property owner should confirm them before selecting meters.
Related engineering resources
Read next
Standards & Codes
UL 891 Switchboards: Scope, Construction and Application
UL 891 is the listing standard for deadfront switchboards, the workhorse of service entrance and low-voltage distribution at 600 V and below. This article explains its scope, the construction and ratings behind the nameplate, how it relates to the NEC and NEMA PB 2, and the limits that push a project toward UL 1558 switchgear instead.
8 min read · Updated 2026-09
Equipment
Switchboard vs. Switchgear: What Actually Differs
Switchboards and low-voltage power switchgear both distribute power at 600 V and below, but they are built to different standards and behave differently under fault, during maintenance and across a service life. This article lays out the concrete differences and the conditions under which each is the right specification.
7 min read · Updated 2026-09
Standards & Codes
NEC Requirements for Switchgear and Switchboards
The National Electrical Code (NFPA 70) sets installation requirements that shape how switchgear and switchboards are specified, laid out and labeled. This article walks through the articles an engineer meets on nearly every project, from Article 408 and working space to fault current marking, arc energy reduction and standby systems, with the reminder that the authority having jurisdiction and the adopted edition govern.
8 min read · Updated 2026-09
Equipment
Automatic Transfer Switches: Types, Transitions and Application
An automatic transfer switch moves a load between a normal source and an alternate source, usually a generator, and the way it makes that move decides what the load experiences. This article covers ATS construction and ratings, the three transition types, bypass-isolation and service-entrance variants, and the timing and code context that govern application.
7 min read · Updated 2026-09
Apex Power Distribution · ApexPower.ai
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