Purpose
This SOP establishes the procedure for safe operation, testing, and maintenance of standby diesel generators in commercial buildings. In Bangladesh, where grid power reliability ranges from 80-95% depending on location, generator systems are not backup but essential operational infrastructure.
Applicable Standards
- NFPA 110 — Standard for Emergency and Standby Power Systems
- ISO 8528 — Reciprocating Internal Combustion Engine Driven AC Generating Sets
- BNBC 2020 Part 8 — Electrical Services
- NFPA 37 — Stationary Combustion Engines and Gas Turbines
Startup Procedure
Automatic Start (ATS-Initiated)
- Mains failure detected by Automatic Transfer Switch (ATS)
- ATS sends start signal after pre-set delay (typically 5-10 seconds)
- Generator cranks and starts (max 3 attempts, 10 seconds each)
- Generator reaches rated voltage and frequency (typically 10-15 seconds)
- ATS transfers load to generator after stabilisation delay (5-10 seconds)
- Total transfer time: 20-35 seconds for standard loads
Manual Start
- Pre-start checks: oil level, coolant level, fuel level, battery voltage, no alarm conditions
- Verify ATS is in manual/test mode
- Start generator from local control panel
- Allow to warm up at no-load for 3-5 minutes
- Transfer load via ATS manual transfer or changeover switch
- Monitor voltage, frequency, oil pressure, coolant temperature
Testing Schedule
| Test Type | Frequency | Duration | Load |
|---|---|---|---|
| No-load run | Weekly | 15-30 min | No load |
| Load bank test | Monthly | 30-60 min | 30-50-75-100% |
| Full load transfer | Quarterly | 2 hours | Actual building load |
| ATS transfer test | Monthly | 15 min | Verify auto-transfer |
| 8-hour endurance | Annually | 8 hours | Full rated load |
Maintenance Schedule
| Task | Frequency | Action |
|---|---|---|
| Visual inspection | Daily | Check for leaks, sounds, alarm panel |
| Oil level | Weekly | Check dipstick, top up if needed |
| Coolant level | Weekly | Check expansion tank |
| Battery | Monthly | Check voltage, connections, electrolyte |
| Oil change | 250 hrs or 6 months | Full oil and filter change |
| Fuel filter | 500 hrs or annually | Replace primary and secondary |
| Air filter | 500 hrs or annually | Replace or clean per OEM |
| Coolant change | Every 2 years | Full flush and refill |
| Major overhaul | 10,000-15,000 hrs | Full engine overhaul |
Fuel Management
- Minimum reserve: 24 hours at full load (NFPA 110 Level 1). In Bangladesh, consider 48-72 hours for critical facilities.
- Fuel testing: Annual fuel quality test (water content, microbial growth, cetane number).
- Fuel polishing: For long-term stored diesel (over 6 months), fuel polishing removes water and particulates.
- Tank inspection: Annual inspection for corrosion, leaks, vent condition.
Generator KPIs
| KPI | Target | Red Flag |
|---|---|---|
| Start reliability | 99% first attempt | Below 95% |
| Transfer time | 30 seconds max | Over 60 seconds |
| Fuel consumption | Within OEM spec +/-10% | Over 15% above spec |
| Oil pressure | Per OEM (40-60 psi) | Below OEM minimum |
| Coolant temp | 80-95C operating | Over 100C |
References
Insights & Guidance
- Weekly no-load test, monthly load bank test, quarterly full-load transfer test per NFPA 110.
- Total power transfer time: 20-35 seconds for standard loads.
- Minimum fuel reserve: 24 hours at full load. In Bangladesh, 48-72 hours for critical facilities.
- Oil change every 250 running hours or 6 months. Major overhaul at 10,000-15,000 hours.
- Start reliability KPI target: 99% first-attempt starts.
In Bangladesh, generators run 2-6 hours daily in many locations. They are not standby equipment but primary infrastructure. A generator that fails to start leaves a building without power, lifts, fire pumps, and IT systems simultaneously.
- Battery failure — the most common cause of generator no-start.
- Fuel contamination — water and microbial growth causes injector failure.
- Wet stacking — running at low load causes unburnt fuel buildup.
- Weekly test run log
- Monthly load bank test report
- Oil change and service records
- Fuel delivery records and quality test results
- Is the generator room clean and ventilated?
- Are oil/coolant/fuel levels adequate?
- Is the battery charger functioning?
- How often is the generator load-tested?
- What is the fuel reserve in hours at full load?
- When was the last oil change?
- Load bank testing — generator service company.
- ATS commissioning — electrical engineer.
- Fuel quality testing — laboratory analysis.