How to Install Electrical Wiring in a Commercial Building

Installing electrical wiring in a commercial building is a complex process that requires expertise, planning, and adherence to electrical codes and regulations. As a licensed electrician, I will walk you through the key steps I follow when taking on commercial wiring projects.

Getting the Required Permits and Documentation

The first step is acquiring the necessary permits and paperwork. This ensures the project follows safety protocols and gets inspected properly.

• I file electrical permit applications with the local building department. This covers things like wiring methods, circuit loads, and required inspections.

• For large commercial buildings, I may need additional permits like plumbing, mechanical, and fire alarm. Each has its own requirements.

• I review the building plans carefully. This helps me fully understand the scope of work and begin planning the wiring layout.

• If it's a retrofit project, I survey the existing electrical system to see what needs upgrading. Older buildings can contain obsolete or insufficient wiring.

Planning the Electrical Load Requirements

Next, I calculate the electrical load needs for the building. This determines the required transformer and panel capacity, wire sizes, and circuit layouts.

• I account for all lighting, receptacles, HVAC systems, kitchen equipment, signage, fire alarms, etc. The equipment nameplate ratings provide load information.

• I consider future expansion plans and potential changes in use. Commercial buildings can change over time. Planning for extra capacity now prevents issues later.

• I use the National Electrical Code (NEC) requirements to size conductors based on voltage drop and ampacity. For complicated loads I may perform thorough load calculations.

• I determine if any special equipment requires three-phase power. The utility company must be contacted early on about providing adequate electrical service.

Developing the Wiring Diagram

With the electrical loads defined, I can draft detailed wiring diagrams to plan out the circuiting.

• Separate branch circuits are created for lighting, receptacles, equipment, etc. I avoid overloading circuits.

• I indicate the wire sizes, overcurrent protection, and any special wiring methods needed.

• Key components like the service panel, subpanels, conduit runs, and junction boxes are located on the diagram.

• I coordinate with other trades to avoid conflicts and ensure sufficient space is allotted for the electrical components.

• For renovations, I carefully mark any circuits being reused versus new wiring to be installed. This helps avoid confusion during construction.

Pulling Permits and Scheduling Inspections

Now I submit the final plans to apply for the required permits and schedule inspections.

• The permit office reviews the plans to verify they meet code requirements. I answer any questions they have.

• Once approved, I pay the permit fees and receive the permit documents. These must be posted visibly onsite.

• I contact the building department to schedule key inspections like the rough-in, final, and service inspections. Inspectors ensure work complies with the approved plans.

• Passing these inspections is required before concealing any wiring or completing the electrical service. The final inspection occurs once all work is finished.

• I keep the marked up permit documents and inspection records on file. They document the project was done properly.

Installing the Electrical Components Safely

With all the prep work done, I start the actual installation process. Safety is my top priority.

• I wear insulated gloves, eye protection, and other PPE when handling live wires. Commercial systems carry dangerous voltage and current levels.

• I keep the work area clean and organized. Tripping hazards and clutter can cause accidents.

• My team and I stay constantly aware of our surroundings onsite. We look out for safety hazards like energized circuits or excavations.

• We use GFCI protection, guard rails, safety ropes/cones, and proper lockout/tagout procedures as needed.

• We review daily tasks together and identify any unique safety considerations before starting work.

Running the Electrical Conduit

Conduit installation comes first since it houses all the wiring through the building.

• The approved wiring method dictates what type of conduit to use - electrical metallic tubing (EMT), rigid metal, PVC, etc.

• I measure and cut conduit to required lengths using appropriate tools like tubing benders and PVC cutters.

• Conduit gets secured with straps or hangers at regular intervals per NEC. I avoid excessive bends or crushed conduit.

• Firestop materials must seal conduit penetrations through fire-rated walls and floors to contain fires.

• Conduit runs to electrical equipment get labeled for easy identification. Spare conduits also get installed for future use.

Pulling and Securing the Wires

Now conductors can be pulled through the conduit system.

• I select the approved wire types sized for each circuit based on the plans. Common options are THHN/THWN-2 or XHHW-2.

• Large wire pulls may require a mechanical puller or lubricant to reduce friction in the conduit.

• I pull neutral and ground wires first, then live wires. Careful coordination ensures wires are not damaged during pulling.

• Cables and conductors get neatly organized and labeled at junction boxes for the different circuits.

• The wires get securely stapled/strapped within 12 inches of junction boxes and at regular intervals per NEC 300.4. This prevents tension or damage.

Installing Receptacles, Lighting, Equipment

With the structure wiring complete, I shift focus to installing receptacles, switches, lighting, equipment, and other devices.

• Receptacles get wired appropriately for single or multi-phase circuits. I verify grounding and polarity at each one.

• Lighting fixtures get mounted and wired per manufacturer instructions and lighting plans.

• HVAC, kitchen equipment, signage, fire alarms, etc. must be wired according to each device's specifications.

• All splices are made with approved connectors like wire nuts or crimp connectors. No loose connections or wires.

• Wires get neatly bundled and labeled at connection points. Excess wire lengths get trimmed off.

Completing the Electrical Service

Finally, I coordinate with the utility company to complete the electrical service installation. This energizes the entire system.

• The service feeders get securely terminated at the service panel based on the wiring diagrams.

• Metering equipment, disconnects, and any other components supplied by the utility get properly installed and connected.

• I obtain the final inspection to ensure all work passed before concealing it in walls or ceilings.

• Once approved, I contact the utility to schedule the service connection. This completes the project!

• I walk the owner through disconnecting power during emergencies. I also provide them documentation of the completed work and inspections.

Following meticulous planning, high safety standards, and electrical codes ensures a successful commercial wiring installation. Let me know if you need help on your next commercial electrical project!