A generator is an engine, so installing one means solving engine problems inside or beside a building: getting enough air in, getting heat and exhaust out safely, storing fuel, controlling noise and vibration, and leaving room to maintain and test it. Many generators that fail when needed were sized correctly but installed in a space that starved them of air, cooked them in their own heat or ran out of fuel.
Indoor room or outdoor enclosure
Generators are installed either in a dedicated room inside the building or in a weatherproof enclosure outside, on a pad or on a roof. Each choice has consequences.
| Question | Indoor room | Outdoor enclosure |
|---|---|---|
| Protection | Protected from weather and tampering | Exposed; enclosure must suit the climate |
| Air and exhaust | Louvres, ductwork and exhaust piping through the building | Built into the enclosure |
| Cold weather | Room stays warmer, easier starting | Needs heaters and suitable fuel |
| Noise | Contained by the building | Needs a sound-attenuated enclosure and careful siting |
| Fire separation | Room construction set by the building code | Separation distances from openings and property lines |
For emergency generators that power life safety loads, the building code and CSA C282 set additional requirements for the location, protection and fire separation of the generator and its fuel, and for how the installation is tested. Check the editions adopted in your province.
Air: combustion and cooling
A running generator needs a large flow of air, mostly to cool the engine. Most of the engine's heat leaves through the radiator, and more radiates from the engine, alternator and exhaust piping into the room. If that heat is not removed, the room temperature rises, the engine derates or shuts down on high temperature, and hot air recirculates back into the radiator.
Good practice for air includes:
- Intake and discharge louvres sized for the airflow the manufacturer specifies, accounting for the louvre's free area and any filters or bird screens.
- Intake and discharge on opposite sides of the room, with the radiator ducted tightly to the discharge louvre so hot air cannot recirculate.
- Motorized louvres that open when the generator starts and are arranged to fail open, or a design that does not depend on them.
- Protection from snow drifting into intakes, and from prevailing winds blowing against the radiator discharge.
- Room heating and engine block heaters to keep the engine ready to start and carry load quickly in winter.
Exhaust
Exhaust is a carbon monoxide hazard and a fire hazard. The exhaust system runs from the engine through a flexible connector, which isolates vibration, then a silencer and piping to a discharge point outdoors. Piping inside the building is insulated or guarded to protect people and nearby materials from its heat, and supported so its weight does not hang on the engine.
Where the exhaust discharges matters as much as how it gets there. It should be well away from air intakes, operable windows, doors and anywhere people gather, and arranged so wind does not push it back into the building. A rain cap or other weather protection prevents water from running into the engine. Exhaust back-pressure must stay within the manufacturer's limit, so long runs with many bends need to be checked.
Fuel
Most standby generators run on diesel; some run on natural gas or propane. Diesel installations usually have a main storage tank, sometimes built into the base of the generator, and often a small day tank near the engine that is refilled automatically by a pump.
Fuel storage is regulated. Tank construction, secondary containment, venting, fill and overfill protection, leak detection and the amount of fuel allowed inside a building are set by the fire code and provincial rules for storage tanks, and some provinces require tank registration. Natural gas and propane supply is installed under CSA B149.1 by licensed gas fitters, and the gas utility must confirm that the supply can deliver enough gas at the right pressure when the generator starts under load.
Fuel quality matters too. Diesel degrades over time and can grow microbes at the fuel-water interface. Plan for fuel sampling, polishing or turnover, and use a winter blend suited to the climate for outdoor tanks. Keep fill points locked and clearly labelled so a delivery driver cannot fill the wrong tank. See our guide to standby generator maintenance.
Structure, noise and vibration
- A concrete housekeeping pad or a structure designed for the generator's weight and vibration, with vibration isolators as the manufacturer specifies.
- Seismic restraint where the building code requires it, which is particularly important in parts of British Columbia.
- Flexible connections for exhaust, fuel and electrical conduit so vibration is not passed into the building.
- Noise control to meet municipal bylaws, especially for outdoor units near property lines and for weekly test runs.
Access, testing and electrical work
Leave room around the generator to service it, replace filters and batteries, and remove large parts. Plan a route for a portable load bank and a connection point for it, because many generators are rarely loaded enough during normal tests; see generator load bank testing. Electrical work includes the generator breaker, feeders to transfer switches, controls wiring, battery chargers and remote annunciation, all installed by licensed electrical contractors under permit. Feeders for emergency systems may need fire protection along their route.
Questions to settle early
- Which loads the generator must serve, and which of them are emergency loads required by code.
- Indoor room or outdoor enclosure, and where the exhaust can discharge safely.
- Fuel type, storage volume and where tanks can go, including how fuel trucks will reach the fill point.
- How the generator, fuel and parts will be delivered and, one day, removed.
- Noise limits at the property line and at neighbouring windows.
- Where a load bank will connect for annual testing.
- Who will maintain it, and whether they have reviewed the layout for access.
Permits come from several directions. A generator project can need building, electrical, gas or fuel storage permits, and in some places an environmental approval for emissions or noise. Identify them at the start so the room, tank and exhaust design satisfy all of them.
How ehZee can help
We design generator installations, including room or enclosure layout, air and exhaust paths, fuel systems, electrical connections and transfer equipment, as part of our emergency and standby power design service. Drawings are sealed by a licensed professional engineer where required. Start with how generators are sized if you are early in planning.
Common questions
Can a generator go on the roof?
Often, if the structure can carry it and fuel, noise and maintenance access can be handled. Roof installations need careful attention to exhaust and intakes, structural support and how parts and fuel will be brought up.
Why does our generator overheat in summer tests?
Common causes are undersized or blocked louvres, a missing or leaking radiator duct that lets hot air recirculate, louvres that do not open, or a hot room. A test run with temperature readings at the intake and radiator usually shows the problem.
How much fuel should we store?
For emergency generators the building code and CSA C282 set minimum run times for the loads they serve. Beyond that, it depends on how long you want to run without a delivery during a regional outage, and on what the fire code allows on your site.