Standby power and generators for Calgary buildings

CCT 01Emergency power versus standby power

The first question is whether the generator is required by the building code or chosen by the owner. The answer changes the design, the permits and the testing.

The current edition of CSA C282, the standard for emergency generator sets, is C282:24. It covers the design, installation, operation, maintenance and testing of generator sets that supply emergency power to buildings where the National Building Code requires it.¹ The code in force references a particular edition, so the design engineer confirms which one applies to your permit.

One generator can serve both emergency and optional loads, but they must be kept apart. Emergency loads get their own transfer switch and wiring, and they get first call on the generator. Optional loads are shed if capacity runs short.

CCT 02Automatic transfer switches and paralleling gear

The transfer switch (ATS) watches the utility supply, starts the generator when the supply fails, moves the load across once the generator is stable, and moves it back after the utility returns. The type decides how the load sees each transfer:

• Open transition (break-before-make). The load sees a short outage on each transfer. This is standard for most emergency and standby systems.
• Delayed transition. The switch pauses in a centre-off position so that large motors and transformers can decay before reconnection. This avoids nuisance trips and torque shocks.
• Closed transition (make-before-break). The generator and utility are briefly paralleled, so the retransfer is seamless. Because the generator connects to the ENMAX system for that moment, the protection scheme must be agreed with ENMAX Power before it is built.
• Bypass-isolation. A second switching path lets the ATS be withdrawn for maintenance without dropping the load. It is worth it wherever the load cannot be shut down.
• Service-entrance rated. The ATS also serves as the service disconnect, which saves a separate main on smaller services.

Larger sites use paralleling switchgear, where several generators synchronize onto a common bus and add or shed load in priority blocks. That gives redundancy (N+1 generators) and lets one unit be serviced while the others stand by. The switchgear side is covered on power distribution and switchgear, and critical-site designs on data centres and critical power.

Homes are different. Alberta's variance for meter-mounted transfer equipment will be archived on January 1, 2027, and new units must then be certified to ANSI/CAN/UL 1008M:2025.²

CCT 03Sizing: it is the starting load, not the running load

Sizing a generator from the total connected load wastes money, and sizing it from the average load fails on the first cold start. A proper load study uses:

• Measured demand. A full year of ENMAX interval or demand data shows what the building really draws, including winter peaks.
• Motor starting. Elevators, fire pumps, chillers and air handlers draw several times their running current when they start. The engineer staggers them in steps with time delays, so the generator is sized for the worst step, not for everything at once.
• Non-linear loads. UPS rectifiers and variable-frequency drives distort the generator's voltage. The alternator and voltage regulator must suit them.
• Elevator regeneration. A descending traction elevator can push power back into a small generator, so a resistive load is needed to absorb it.
• Derating. Engine output falls with altitude and high intake temperatures. The manufacturer's derating curves apply at Calgary's elevation.

Long runs from a generator pad to the transfer switch also need a voltage-drop check. The voltage drop calculator gives a first estimate.

CCT 04Calgary conditions: cold starts and demand peaks

Calgary's January design temperatures are −30 °C at 2.5% and −32 °C at 1%.³ Demand peaks in both winter and summer. Alberta's all-time peak demand of 12,785 MW was set on December 11, 2025,⁴ and its summer record of 12,221 MW on July 22, 2024.⁴ A generator may be called on in either.

For a winter-ready installation, specify:

• jacket-water block heaters and battery heaters, with an alarm at the fire alarm or building automation panel if they lose power
• winter-blend diesel, with tank heating or a turnover plan, or a natural gas supply confirmed at full flow during a cold spell
• enclosures, louvres and exhaust placed so that drifting snow cannot block them. Rooftop enclosures and dunnage must also account for Calgary's ground snow load of 1.1 kPa, which the structural engineer uses to design the roof.³
• a monitored battery charger. Weak starting batteries are a frequent cause of failed starts.

More on cold-weather electrical is in winter electrical in Calgary.

Film 08 · Standby power · illustrative film

CCT 05Permits and the life-safety connection

A commercial generator installation in Calgary needs an electrical permit, obtained by a master electrician's contractor.⁵ Where the service or the generator switchgear is 600 A or more, the City requires plans and drawings.⁶ The pad, enclosure or fuel storage may need a building permit or fire review as well, so check with the City before ordering equipment. Airdrie, Cochrane, Okotoks and Rocky View County sites apply to their own permit authorities.

Emergency generators usually connect to the fire alarm system, which reports generator running, generator trouble and low fuel. In Calgary, altering or installing a fire alarm needs both an electrical permit and a building permit.⁶ Where the building needs professional involvement, the fire alarm submission needs an Alberta professional engineer's stamp, including a final verification.⁷ The system must be verified to CAN/ULC-S537,⁸ so any new generator supervisory points are tested and recorded.

Emergency lighting supplied from unit equipment has its own rule: the receptacles must be at least 2.5 m above the floor where practicable and within 1.5 m of the unit.⁹ Multi-family towers bring all of this together. See multi-family and high-rise.

CCT 06Commissioning, exercising and load banks

A generator that only idles on its weekly exercise is not proven. Commissioning should include:

1. A load-bank test at rated load for the duration in the specification, so that the engine, cooling and alternator are proven at full output.
2. A building load test. The utility main is opened and every transfer switch transfers, sheds and restores in its programmed sequence.
3. Fire alarm verification of the generator's supervisory signals.
4. Documentation: settings, test records and the switching sequence, left in the generator room.

After handover, emergency generators follow the testing schedule in CSA C282 and the fire code. Diesel sets that spend their life lightly loaded also benefit from periodic load-bank runs, which burn off the unburned fuel and carbon that build up in the exhaust ("wet stacking"). Standby sets should be exercised under real building load whenever the owner can accept a transfer. Generator and ATS testing fits naturally into the wider program on maintenance and thermography.

CCT 07What drives the price

No federal, Alberta or City of Calgary source publishes installed prices for commercial generators, and the spread between a small office standby set and a tower's emergency plant is too wide for one range to mean anything. A contractor prices:

• Generator rating and fuel: diesel with an integral tank, or natural gas with a new gas service
• Transfer equipment: the number of ATSs, bypass-isolation, closed transition or paralleling switchgear
• Location: pad at grade versus rooftop (crane, structure, dunnage), and the distance to the electrical room
• Enclosure: sound attenuation and winter packages
• Life-safety interfaces: fire alarm points and verification, and engineering stamps
• Commissioning: load-bank rental and after-hours building transfer tests
• Permits: priced on construction value at $112 plus $9.79 per $1,000, plus the Safety Codes Council fee¹⁰

The residential side is broken down in generator installation cost, and the utility side in the ENMAX service connection guide. When the loads and site are known, request a quote and a person replies.