A standby generator spends almost all of its life sitting still, and then it has to start and carry the load the moment the utility fails. Regular inspection, exercise under load and planned service are what make that possible. A generator that is only looked at when the power goes out is the one most likely to let you down.
Why standby generators fail
Most failures to start or carry load come from a short list of causes, and nearly all of them are preventable with routine maintenance:
- Batteries. Weak, sulphated or poorly connected starting batteries are the most common reason a generator will not crank.
- Fuel. Water, microbial growth and degraded fuel plug filters and starve the engine. See diesel fuel quality and storage.
- Cooling system. Low coolant, failed block heaters, cracked hoses and blocked radiators.
- Controls left in the wrong mode. A control switch left in "off" or "manual" after maintenance means the set will not start automatically.
- Transfer equipment. A generator that runs but never takes the load is no help. See automatic transfer switches.
- Light-load running. Diesel engines that are only ever run with little or no load build up unburned fuel and carbon, a problem called wet stacking.
Standards and requirements
In Canada, emergency generators that supply life safety loads in buildings are generally covered by CSA C282, Emergency electrical power supply for buildings, which the building and fire codes reference. It sets out installation requirements and a schedule of inspection, testing and maintenance, including regular run tests and periodic tests under load. The National Fire Code of Canada and the provincial fire codes in Alberta, BC and Ontario point to these requirements for existing buildings. Check the current edition adopted in your province, and any requirements set by your local fire authority.
Generators that serve only business loads, such as a data centre or a process, may not fall under C282, but the same maintenance logic applies. Manufacturer service schedules are a baseline in either case.
What a maintenance program covers
Frequent checks
Short visual and operational checks, usually done weekly by trained building staff or a service contractor, catch most problems early:
- Control panel in automatic mode with no alarms showing
- Battery charger working and showing normal voltage and current
- Block heater keeping the engine warm
- Coolant, oil and fuel at correct levels
- No leaks of fuel, oil or coolant under the set or around the tank
- Air intake and radiator clear of debris, snow and stored materials
- Enclosure or room secure, clean and properly ventilated
Regular run tests
Generators should be started and run on a regular schedule. The test should prove the full sequence: the engine starts, reaches voltage and frequency, and the transfer switch moves the load. Where possible, run the set under building load rather than with no load, and run it long enough for the engine to reach normal operating temperature. Record start time, voltages, frequency, oil pressure, coolant temperature and any alarms.
Periodic service
On the schedule set by the manufacturer and the applicable standard, a qualified technician should:
- Change oil, oil filters, fuel filters and air filters
- Test coolant condition and freeze protection, and check belts and hoses
- Load-test or replace starting batteries and clean terminals
- Inspect the exhaust system for leaks, supports and rain caps
- Check the governor, voltage regulator and safety shutdowns
- Sample fuel and check the tank for water
- Exercise and inspect the transfer switch
Load testing
Building load is often far below the generator's rating, so routine run tests may not prove that the set can carry its full output. Periodic testing with a load bank fills that gap and burns off deposits from light-load running. See our guide to generator load bank testing.
Put it back in automatic. After every test or service visit, confirm that the generator controls and the transfer switch are back in automatic mode, and that no alarms or bypasses are left active. Make this the last line on every checklist.
Records
Keep a log at the generator and a copy on file. For each test and service visit, record the date, who did it, run time, readings, any problems found and what was done. Fire inspectors and insurers may ask for these records, and they are the best way to spot trends such as rising coolant temperature or longer start times. A good log also makes it easy to show that required tests were done.
Cold climate considerations
In Canadian winters, block heaters, battery condition and fuel cloud point matter more than anywhere else. Check block heaters and battery chargers before the first cold snap, clear snow from intakes and exhaust, and make sure the fuel in the tank is suited to the lowest temperatures it will see.
A typical case
Consider an office building with an emergency generator that has passed its monthly run test for years. Each test is started from the control panel with no load, runs for a few minutes, and is logged as "OK". Then a winter storm takes out the utility overnight. The generator cranks slowly, starts on the third attempt, and the transfer switch moves the load. Twenty minutes later the set shuts down on low coolant level.
Looking back, the warning signs were in the log: start times had been creeping up, and nobody had recorded coolant level or battery voltage. The batteries were past their service life, a radiator hose had been weeping for months, and short no-load runs had never brought the engine to temperature, so the leak only showed under real operation. None of these faults was unusual or expensive. What was missing was a program that tested the whole sequence under load and recorded enough readings to show a trend.
Questions to ask your service contractor
- Which standard and schedule are you following for this generator, and does it match what our province and fire authority require?
- Do monthly tests transfer the building load, and for how long does the engine run?
- How old are the starting batteries, and how are they tested?
- When was the fuel last sampled, and what did the results show?
- When was the last load bank test, and is one due?
- What readings do you record at each visit, and can we see the trend?
- Who confirms that the controls and transfer switch are back in automatic before you leave?
Common mistakes
- Testing the engine but not the transfer. A run test started from the generator panel does not prove that the transfer switch will sense a utility failure and move the load.
- Logging "OK" instead of readings. Without numbers there is no trend, and slow deterioration goes unnoticed.
- Replacing batteries only after they fail. Starting batteries are cheap compared with a failed start. Replace them on age and test results.
- Storing things in the generator room. Boxes and equipment block airflow, add fire load and get in the way of service.
How ehZee can help
Our diesel generator inspections review the condition of the generator, fuel system, batteries, controls and transfer equipment, and look at your test and maintenance records against the schedule that applies. We report what we find and what to address first, and can coordinate the follow-up work with your service contractor.
Common questions
How often should a standby generator be run?
Regularly, on the schedule set by CSA C282 for emergency generators or by the manufacturer for other sets. Monthly testing under load is a common baseline, with weekly visual checks in between. Confirm the frequency that applies to your building.
Is running the generator with no load good enough?
It proves the engine starts, but repeated no-load runs can cause wet stacking in diesel engines. Testing with the building load or a load bank is better.
Who can maintain an emergency generator?
Simple visual checks can be done by trained staff. Service, repairs and electrical work should be done by qualified technicians, and some provinces require specific licensing for electrical work on the transfer equipment.
How long do generator starting batteries last?
Service life depends on battery type, temperature and charger condition. Many owners replace them on a fixed interval recommended by the manufacturer or their service contractor, and sooner if testing shows weakness.