How to Care For a Diesel Generator

Firstly, Note the General Care Protocol For Diesel Generators

  • Prime Rated Generators are designed to run with 10% overload for 1 hour in any 12 hour period.
  • Standby Rated Generators are designed to run at 100% load for the duration of an outage, with no overload available.
  • Moreover, the load MUST be reasonably balanced/distributed across all the three phases.
  • The AMF panel used correctly in accordance with manufacturer’s instructions.
  • Maintenance carried out every 6 months by a qualified generator engineer.
  • A test certificate issued each service/maintenance visit every 6 months. Additionally, only approved parts are used.
  • All work and maintenance records kept available.
  • It goes without saying, any irregularities visual or otherwise are reported in writing immediately.
  • All fuel, oil, water and other fluid levels to be kept full.
  • Ensure the generators never allowed to run out of fuel or oil. Especially whilst holding the load.
  • Importantly, never over-load or allow the Generator to run lightly loaded for long periods.
  • Schedule to run off load once every week for a test of 5 minutes maximum.
  • Perform a run with load once a month.
  • Generator enclosure checked for possible tampering. For example, emergency stop button been pressed and not reset?
  • Someone appointed as the responsible person to overlook implementation.


Diesel Generator Service Program

A regular generator service program should include tests and checks of the following:

Cooling System

  • Radiator/heat exchanger
  • Coolant
  • Hoses and connections
  • Fan drive pulley and Fan
  • Fan belts
  • Jacket water heater
  • Water pump
  • Thermostats

Fuel System

  • Water trap/separator of fuel tank
  • Connections and fuel lines
  • Governor and controls
  • Fuel filters – primary/secondary
  • Fuel pressure
  • Exhaust system and air induction
  • Air filter
  • Service indicator of air filter
  • Air inlet system
  • Turbocharger
  • Exhaust manifold
  • Valves and valve rotators

Lubrication Oil System

  • Oil
  • Filters
  • Oil pressure
  • Crankcase breather

Starting System

  • Batteries
  • Battery specific gravity
  • Battery charger
  • Starting motor
  • Alternator
  • Engine monitor and safety controls
  • Gauges
  • Remote annunciators/alarms


  • Bearings
  • Slip rings and brushes
  • Space heaters
  • Vibration isolators

Control Panel

  • Start controls – manual/auto
  • Voltmeter
  • Ammeter
  • Frequency meter
  • Circuit breaker
  • Auto transfer switch

Gas Engine

  • Gas lines and connections
  • Carburettor and linkage
  • Magneto/distributor
  • Ignition system
  • Spark plugs

Insulation Test

  • Main stator
  • Main rotor
  • Exciter stator
  • Exciter rotor

Load Testing

With full load, perform a two to four hour load test.

Overall Energy Systems Testing

Furthermore, it is important to test the entire system on a regular basis.
As well as with performing the periodic Planned Maintenance.
Likewise an overall system test involves putting the critical load at risk, so careful arrangements must be in place.

Mains Failure Test

Firstly, disconnect the mains supply to the protected power equipment. Do this for an extended period and check, without generator:
1. When the UPS is fitted with auto-restart facilities, the system will return to normal operation automatically. Otherwise all UPS modules can be re-started manually and the system restored to normal operation.
2. Finally, reset all alarms.

Generator installation:

Primarily, check the Automatic Mains Fail operates correctly. (AMF equipment)
The UPS signals a mains failure during the changeover.
At the same time, the generator shuts down after the expected time.
While the UPS accepts the restored mains power supply and recharges the batteries.
Finally, reset all alarms.

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