A significant share of Ontario’s manufacturing and industrial facilities were built and electrically commissioned in the 1960s, 1970s, and 1980s. These buildings have served their owners for decades, have typically been modified incrementally as production requirements changed, and in many cases have never had a formal engineering review of their electrical distribution systems. When these facilities commission their first arc flash study, the process — and the findings — often differ substantially from what a newer or better-documented facility experiences.
Understanding what to expect when an older Ontario facility goes through an arc flash study for the first time helps EHS managers and plant engineers prepare realistically and budget accurately.
What Makes Older Facilities Different for Arc Flash Studies
Missing or Inaccurate Single-Line Diagrams
The most common challenge at older Ontario facilities is the absence of current, accurate single-line diagrams (SLDs). Many buildings constructed before the 1990s had SLDs produced at initial commissioning — paper drawings that have not been updated to reflect four decades of electrical system modifications, panel additions, transformer replacements, and service entrance changes. Some facilities have no surviving SLDs at all.
Without accurate SLDs, an arc flash study provider must document the electrical system from scratch during the site visit — tracing cables, photographing nameplates, mapping connections, and building the SLD from field observations. This process adds significantly to field time (typically two to four additional days for a 50-node facility) and to study cost (typically 25–30% above the standard rate for facilities with current SLDs). The resulting SLD, however, becomes a valuable permanent record that the facility did not previously have.
Preparation: Before engaging a provider, search for any surviving drawings — commissioning drawings, as-built markups, panel schedules, utility company records. Even partial or inaccurate drawings give the provider a starting framework that reduces field documentation time. Ask your facilities maintenance team what documentation exists and where it is stored.
Undocumented System Modifications
Older facilities carry decades of undocumented electrical system changes. A panel added to support a new production line in 1992. A transformer replaced after a failure in 2001 with a unit of slightly different impedance. An MCC expansion in 2008. A contractor-installed relay setting change in 2015 that nobody recorded. Each of these changes affects the power system model and, potentially, the arc flash calculations.
The arc flash study site visit for an older facility typically uncovers several discrepancies between the building’s nominal electrical configuration and its actual as-found condition. An experienced provider treats this as expected — their field data collection process is specifically designed to capture what is actually installed, not what the facility thinks is installed. Less experienced providers who rely on facility-provided information without thorough independent verification produce models that reflect what the facility believes about its system rather than what the system actually is.
Preparation: Ask your electrical maintenance team to document as many known system changes as possible before the provider’s site visit. Even an informal list — “we replaced the main transformer in 2018,” “we added three panels in the east wing in 2021” — significantly improves field efficiency. Also gather any equipment documentation you do have: current transformer nameplates, recent contractor invoices for electrical work, relay setting documentation from any recent relay work.
Aging Protective Devices With Uncertain Settings
Older circuit breakers — thermal-magnetic frame breakers installed in the 1970s and 1980s — have time-current characteristics that can drift over decades of operation. The published curves for these devices, used in coordination studies, assume the device is performing as designed. A 40-year-old breaker that has been operated many times, has been exposed to fault currents, and has never been maintained may not actually perform according to its published curves.
More significantly, older electromechanical protective relays — common at larger industrial facilities and utilities from this era — often have settings that are: inconsistently documented, set to values that made sense for the original system configuration but are no longer appropriate, or simply unknown because the original commissioning documentation has been lost.
For Peterborough’s older manufacturing facilities and Niagara Falls’ legacy industrial operations — many of which have electrical systems with equipment originating in the 1970s and 1980s — the coordination study at the time of first arc flash study commissioning frequently reveals protection settings that are significantly different from what would be specified if the system were designed today. These findings produce setting recommendations that, when implemented, can substantially reduce arc flash incident energy at affected locations — but may also reveal equipment that needs to be inspected, tested, or replaced before it can be relied upon to clear faults as the study assumes.
Preparation: Collect whatever relay setting documentation exists. If you have recently had any electrical work performed by an outside contractor, ask whether they recorded the settings they found or any they changed. Be prepared for the possibility that the coordination study recommends maintenance on aging protective devices — this is valuable information, not an unexpected complication.
Higher-Than-Expected Incident Energy Levels
A common experience at older Ontario facilities receiving their first arc flash study is that incident energy values at some locations are significantly higher than informally expected. There are two primary reasons:
Outdated protection settings. As described above, protection devices in older systems often have slow time-delay settings that were appropriate for the system as originally configured but have not been revisited as the system evolved. Slow clearing times mean higher incident energy.
Larger utility service transformers. Many Ontario facilities upgraded their utility service capacity over the years — from the 500 kVA transformer that served a smaller original operation to a 1,500 or 2,000 kVA transformer that serves current production demands. The higher-capacity transformer supplies significantly higher fault current at the service entrance switchgear, which increases incident energy at main switchgear bus locations. An older facility with a historically modest electrical system that has received transformer upgrades may discover that its main switchgear has Category 3 or 4 incident energy levels that no one had anticipated.
The first arc flash study at such a facility produces findings that require action: PPE procurement at higher categories than currently stocked, potential protection setting changes to reduce clearing times, and possibly engineering evaluation of whether arc flash mitigation measures (current-limiting fuses, zone-selective interlocking) would bring high-energy locations to more manageable levels.
What the Study Delivers — Beyond Compliance
For older Ontario facilities, the first arc flash study produces value beyond CSA Z462 compliance documentation. The study’s byproducts include:
A current, accurate single-line diagram. For many older facilities, the SLD produced by the arc flash study is the first accurate electrical system documentation the facility has had in years. This document is valuable for maintenance planning, emergency response, expansion planning, and future contractor work.
A verified equipment inventory. The field data collection process produces a current inventory of every panel, MCC, and transformer in scope — with nameplate data, location, and rating. This inventory is often more accurate than whatever equipment records the facility maintains internally.
Coordination findings and setting recommendations. The coordination study typically produces actionable recommendations for protection setting changes that reduce clearing times, improve fault coordination, and directly reduce arc flash incident energy levels at multiple locations. Implementing these recommendations often reduces the required PPE category at high-energy locations — sometimes enough to eliminate the need for Category 3 or 4 PPE at some MCC buses.
A baseline for future updates. The power system model built during the first study becomes the foundation for all future five-year updates. Once the model exists, updates are significantly faster and less expensive than the initial study — the investment in thorough initial documentation pays dividends for the full lifecycle of the electrical system.
Budgeting for an Older Facility Study
Ontario EHS managers budgeting for a first arc flash study at an older facility should plan for the upper end of the cost range for their facility size. The combination of missing SLDs, undocumented system modifications, and potentially aging protective devices means older facilities almost always require more field time and more engineering time than equivalently sized modern facilities with complete documentation.
Practical budget guidance:
- Add 25–30% to the standard cost estimate if SLDs are absent or significantly outdated
- Budget for the coordination study as a required component, not an optional add-on — for older facilities with uncertain protection settings, the coordination analysis is where the most actionable value is produced
- Allow for the possibility that the study will identify equipment that requires maintenance (relay inspection, breaker testing) alongside the arc flash deliverables
Our arc flash study guide covers what a complete study involves and what the deliverables include. If your facility is older and you are uncertain about the applicable cost range, our free cost estimator will give you a starting point — and our provider network includes engineers with extensive experience at Ontario facilities where documentation starts from scratch.