An electrical shop drawing review is a formal engineering evaluation where a consulting engineer checks a manufacturer's detailed fabrication drawings against the approved contract documents. It confirms that switchgear, panels, lighting fixtures, and mechanical equipment hookups match the design intent, equipment ratings, and Canadian Electrical Code standards before fabrication begins. This quality gate prevents expensive site modifications, equipment rejections, and project delays.
What an Electrical Shop Drawing Review Entails
In commercial and institutional construction, design drawings show the functional layout and performance ratings of the building systems. They do not show factory-level assembly details. The contractor and their equipment vendors produce shop drawings to detail how equipment will be manufactured, wired, and assembled.
A shop drawing submittal package typically includes:
- Manufacturer specification sheets (cut sheets) highlighting model numbers, options, and finishes.
- Internal schematic and single-line wiring diagrams showing breaker frames, trip settings, and control relays.
- Physical dimensional outlines showing conduit entry zones, weights, and clearance working spaces.
- Testing certifications from accredited bodies such as CSA, cUL, or Intertek (ETL).
When the engineer receives these submittals, they review them for compliance with the contract specifications and design calculations. The review ends with a stamped disposition:
| Review Stamp Status | Meaning Under Contract | Contractor Action Permitted |
|---|---|---|
| Reviewed | No exceptions taken; submittal conforms to design intent. | Order materials and fabricate equipment immediately. |
| Reviewed as Noted | Minor revisions or clarifications noted directly on the drawing. | Proceed with fabrication while incorporating the marked changes. |
| Revise and Resubmit | Significant deviations or missing critical engineering parameters. | Do not fabricate. Correct marked items and submit a revised package. |
| Rejected | The submittal does not meet contract requirements or specified equipment type. | Do not fabricate. Provide an alternative product that complies with specifications. |
Engineering Standards and Code Governance
In Alberta, the practice of reviewing shop drawings falls under the professional obligations established by the Association of Professional Engineers and Geoscientists of Alberta (APEGA). APEGA's practice standards dictate that an authenticating Professional Engineer remains responsible for ensuring that the constructed facility meets safety, health, and building regulations.
Under the Canadian Electrical Code (CEC 2024, CSA C22.1:24), several core principles guide every equipment review:
- Equipment Certification (Section 2): Electrical equipment installed in Alberta must bear acceptable Canadian certification marks recognized by the Standards Council of Canada and Alberta Municipal Affairs. Non-certified equipment requires special field evaluation before site energization.
- Electrical Load and System Sizing (Section 8): Submittals must align with the engineer's electrical load analysis. If an installed mechanical unit has a higher minimum circuit ampacity (MCA) than what was calculated in the original design, the upstream breaker and conductors must be recalculated.
- Overcurrent and Fault Interruption (Section 14): Equipment interrupting ratings must withstand or safely interrupt the available short-circuit current delivered by the utility service.
Shop drawing review is not a substitute for field supervision. The engineer confirms the equipment concept matches the contract design. The electrical contractor remains legally responsible for jobsite dimensions, rough-in coordination, and installation workmanship.
Application to Distribution Equipment: Worked Example
To understand how this functions on a real project, consider a commercial electrical design in Alberta for a multi-tenant commercial bay in Edmonton. The contract documents specify a main secondary distribution panelboard fed at 120/208 V, 3-phase, 4-wire.
Defining the Parameters
Before reviewing the equipment submittal, the engineer reviews the electrical load calculation. To define electrical load in practical terms: an electrical load is the total amount of electrical power consumed by all connected equipment on a circuit, measured in kilowatts (kW) or kilovolt-amperes (kVA).
What parameter indicates the electrical demand on a system? The peak electrical demand load indicates system demand. It represents the maximum rate of energy consumption observed over a set monitoring period (typically 15 minutes), expressed in amperes (A) or kVA. It is rarely the sum of all connected nameplates because not all devices run simultaneously.
To calculate this, the engineer applies a demand factor in electrical design. The demand factor is the ratio of the maximum demand of a system to the total connected load. For example, if a kitchen has 50 kVA of total connected small appliances, CEC Section 8 rules allow an engineer to apply specific demand percentages rather than sizing the service conductors for 100 percent continuous duty.
The Review Checklist
In our Edmonton commercial project, the calculated peak demand load is 310 A. The engineer specified a 400 A main breaker panelboard with a minimum short-circuit interrupting capacity (AIC) of 25,000 A (25 kA) symmetrical, based on EPCOR utility supply data. You can verify fault withstand requirements using a voltage drop and SCCR calculator during the design stage.
When the vendor submits the 400 A panelboard submittal, the engineer checks five specific items:
- Main Bus Rating: The shop drawing specifies a copper bus rated for 400 A continuous duty. This satisfies the 310 A demand calculation with appropriate margin.
- Interrupting Rating: The submittal specifies branch and main breakers rated at 22 kA. The engineer rejects this line item, noting that the contract requires a minimum of 25 kA symmetrical interrupting rating to withstand local utility fault levels.
- Certification: The submittal cut sheet clearly indicates a cULus listing mark suitable for installation in Canada.
- Physical Dimensions and Enclosure: The submittal calls for a Type 1 (NEMA 1) general-purpose indoor enclosure. The electrical room architectural layouts show sufficient front working clearance meeting CEC Section 2 requirements.
- Sub-feed Breakers: The submittal includes the specific breaker frame and trip sizes specified for the downstream tenant subpanels.
Because the interrupting rating failed to meet the specified 25 kA threshold, the engineer stamps the drawing Revise and Resubmit. Catching this mismatch at the drawing stage prevents the vendor from building a switchboard that an Alberta safety codes officer would fail during final inspection.
Common Misconceptions in Submittal Reviews
Project teams often stumble over procedural details during construction administration. The four most common misconceptions include:
- "Reviewed" means field approval: An engineer's stamp does not confirm that the unit fits physically into a mechanical alcove. Field measurements remain the sole responsibility of the trade contractor.
- Substitutions are automatically accepted through submittals: Contractors sometimes submit an alternate manufacturer's cut sheet without filing a formal Substitution Request. Engineers can reject unapproved substitutions without a technical review, as standard contracts require prior approval for voluntary alternates.
- Shop drawings replace permit support: Having reviewed shop drawings does not grant permission to begin work on site. A valid commercial electrical permit issued by the municipal authority having jurisdiction (such as the City of Edmonton or City of Calgary) is mandatory before installing wiring.
- Only switchboards require review: Specialized systems like fire alarm components, variable frequency drives, emergency battery units, and lighting controls require equal technical scrutiny. Overlooking lighting control submittals can lead to violations of the National Energy Code of Canada for Buildings (NECB 2020).
Related Requirements: Permits, Fees, and Field Reviews
In institutional electrical design, such as healthcare spaces or secondary schools, submittals require coordination with specialized standards, including CSA Z32 for patient care areas. Coordination studies and arc flash analysis submittals must also be verified alongside the distribution gear.
Commercial electrical permit applications require engineered drawings authenticated with an APEGA professional seal. During design development, engineering fees depend on project size, system complexity, submittal turnaround speed, and scope. To obtain specific engineering pricing for your project, contact our team directly at 825-438-1945 for a formal proposal.
Permit fees collected by municipalities are separate from engineering costs. In Alberta, municipal commercial electrical permit fees are established by municipal bylaws and typically scale based on the total installation value of the electrical work, alongside a mandatory Safety Codes Council surcharge. Current fee schedules are publicly available through your local municipality (such as the City of Edmonton Planning and Development Services or City of Calgary Building Services).
Once shop drawings are reviewed and equipment arrives on the jobsite, the design team performs scheduled general reviews. The engineer compares the installed equipment against the approved submittal package. Any deviations are logged directly onto an engineering deficiency punch list. For field checklists and resolution protocols, read our guide on Deficiency List Electrical: Field Review Checklist, or explore our complete suite of electrical engineering services in Alberta.
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