Regular service and maintenance of standby power generators are absolutely essential for ensuring dependable operation during unexpected power outages. Without proper care, even the most reliable generator can fail when it is needed most, leading to costly downtime and potential hazards. Preventative maintenance is designed to detect and remedy small issues before they escalate, thus safeguarding the generator’s readiness and your peace of mind.

A comprehensive maintenance schedule should include a variety of tasks performed at regular intervals, with each check serving a vital role in overall generator health. Specific tolerances must be observed to ensure peak performance these may vary between manufacturers we will insure OEM checks are followed and OEM tolerances are checked:

• Visual inspections for leaks, corrosion, or loose connections:     Oil, fuel, or coolant leaks should have zero tolerance—any leak, no matter      how minor, must be repaired immediately. Corrosion on terminals should be      addressed if it exceeds a film thicker than 0.1 mm. Fasteners and      connectors must be torqued to manufacturer specifications, typically      within ±5% of the recommended value.
• Testing and tightening of electrical and mechanical components:     Electrical connections should have a resistance no greater than 0.2 ohms      at joints. Mechanical belt tension should be within ±10% of manufacturer      specification, and pulley alignment deviation should not exceed 2 mm over      a one-metre span. Moving parts must operate smoothly, with free play      within manufacturer’s tolerance, usually less than 2 mm for linkages.
• Changing engine oil, oil filters, and fuel filters: Engine oil level must be      maintained within the upper and lower marks on the dipstick (tolerance      typically ±0.2 L for most gensets). Oil pressure during operation should      fall within the range specified in the manual (often 2.0–5.0 bar). Fuel      filter differential pressure should not exceed 0.5 bar; if it does, the      filter must be replaced. During each oil change, a sample of the old oil      should be taken and analysed for contaminants, metal particles, and      viscosity; this assessment provides valuable insight into the internal      condition and wear of the engine. Additionally, each filter, including oil,      coolant and fuel filters, will be opened and carefully inspected for the      presence of metal fragments, shavings, or any debris that could indicate      abnormal engine wear or potential early failure. Any foreign material      detected will be documented and investigated to address root causes before      they become critical issues.
• Inspecting and flushing the cooling system, checking coolant level and condition: Coolant level must be within ±10 mm of the “full” mark when cold.      Coolant concentration (antifreeze mix) should maintain a freezing point of      at least –34°C; pH should be between 7.0 and 8.5. Radiator cap pressure      tolerance is typically ±0.05 bar from the rated value.
• Testing and replacing batteries: Battery voltage should remain within 12.6 V to      12.8 V for fully charged 12 V batteries, with a minimum cranking voltage      of 9.6 V under load. Terminal resistance must be less than 0.05 ohms, and      electrolyte levels should cover the battery plates by at least 10–15 mm      for serviceable batteries. The battery charging voltage should be      maintained between 13.5 V and 14.5 V during the charging process to ensure      optimal battery health and performance; values outside this range may      indicate a faulty charging system or risk of battery damage.
• Examining exhaust systems for obstructions and ensuring proper ventilation:     Exhaust back pressure should not exceed the generator manufacturer’s      limit, typically 7.5 kPa (30 in H2O); any observed restriction      must be corrected. Clearance from combustible materials must meet local      codes, but generally at least 1 metre.
• Cleaning and replacing air filters: Air filter restriction should not exceed 250 mm      H2O (10 in H2O) as indicated by the service      indicator or manufacturer’s specification. If the pressure drop exceeds      this value, the filter must be replaced. Ensure there is no visible damage      or breaks in filter media.
• Running the generator under load: During load bank testing, voltage output should      remain within ±5% of rated value (e.g., 230 V ±11.5 V), and frequency      deviation should be less than 2%. The generator must respond to load      changes within 2 seconds and stabilise voltage and frequency within      tolerance.

Regular inspection and adjustment of engine tappets (valve clearance) and timing are vital for maintaining optimal engine performance and longevity. Incorrect valve clearance or timing can lead to poor combustion, increased wear, and even catastrophic engine failure.

• Tappet (Valve Clearance) Check: Measure valve clearance when the engine is cold, using a feeler      gauge. Typical clearance values vary by engine model but generally fall      within the range of 0.20 mm to 0.35 mm for intake valves and 0.35 mm to      0.50 mm for exhaust valves. Tolerances are often ±0.02 mm. Adjust the      tappet screws to manufacturer-specified values, ensuring even clearance      across all cylinders.
• Engine Timing Inspection: Check the alignment of timing marks on the crankshaft and      camshaft. Timing deviation should be within ±1 degree of the specified      value. For engines with timing belts or chains, inspect for slack,      excessive wear, or misalignment. Adjust or replace components as necessary      to restore precise timing. Incorrect timing can cause rough running,      backfiring, or engine damage.

After adjustments, always recheck clearances and timing with the engine rotated through several cycles to confirm settings remain consistent. Document all findings and corrective actions in service records for future reference.

In addition to these checks, technicians must use parts that meet or exceed OEM specifications and maintain the generator in a clean, dry environment. Outdoor units require enclosure integrity with no gaps greater than 3 mm to prevent pest entry, and no visible rust deeper than 0.5 mm on structural components.

During the service and maintenance of standby generators, strict adherence to COSHH (Control of Substances Hazardous to Health) regulations is mandatory. Many substances used or encountered—such as engine oils, coolants, battery acids, cleaning solvents, and diesel fuel—are hazardous to human health if not properly managed.

• Technicians must assess all      substances present on site and consult Safety Data Sheets (SDS) for      guidance on safe handling, storage, and disposal.
• Appropriate personal protective      equipment (PPE), such as gloves, goggles, and protective clothing, must be      worn when handling hazardous substances.
• Spill kits and containment      measures must be available and used immediately in the event of leaks or      accidental releases.
• Hazardous waste, such as used      oils, contaminated filters, oily rags, and batteries, must be disposed of      through licensed waste disposal channels in accordance with COSHH and      local environmental regulations.
• All risk assessments and COSHH      records must be kept up to date and accessible for inspection.

Implementing COSHH protocols protects both personnel and the environment, ensuring safe working conditions and regulatory compliance during all maintenance activities.

A comprehensive site service log is maintained to document all checks, measurements, adjustments, and observations carried out during each maintenance visit. This log serves as an official record, supporting regulatory compliance, warranty claims, and future troubleshooting.

• Checklist completion: Every maintenance task—visual inspections, electrical tests,      mechanical adjustments, fluid changes, filter inspections, coolant and      battery checks, engine timing and tappet adjustments, load tests, and      COSHH compliance—is itemised and ticked off as completed.
• Parameter recording: All measured values, such as oil pressure, coolant level, battery      voltage and charging voltage, valve clearances, timing marks, and filter      condition, are recorded alongside their respective tolerances and any      deviations found.
• Findings and corrective actions: Observations (e.g. presence of debris in      filters, evidence of leaks, corrosion, or loose connections) and all      corrective actions (repairs, replacements, adjustments) are detailed, with      parts and materials used clearly listed.
• Oil and filter analysis: Old oil samples and opened filters are logged, with any detected      contaminants or metal shavings described and recommendations for follow-up      documented.
• COSHH and safety compliance: Each use of PPE, reference to SDS, or hazardous waste disposal is      noted to demonstrate adherence to safety procedures.
• Sign-off and review: The service log is signed and dated by the technician and, where      required, countersigned by the site representative. Any recommendations      for further work or monitoring are noted for follow-up visits.

Maintaining an accurate and detailed site service log ensures transparency, helps identify recurring issues, and provides a clear maintenance history for the standby generator, contributing to its ongoing reliability and compliance.

All maintenance activities should be documented with precise readings, noting any deviations from tolerance, corrective actions taken, and parts replaced. Such diligence ensures warranty protection, supports troubleshooting, and forms a clear timeline for future checks. Adhering to these standards extends the operational life of your standby generator and assures continuity during critical power interruptions.