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IS 15228:2002 is the Indian Standard (BIS) for installation, testing and maintenance of emergency and standby power systems. This code establishes minimum requirements for the installation, performance, testing, and maintenance of emergency and standby power systems. It provides a framework for classifying systems based on their criticality (Level), power restoration time (Class), and duration of supply (Type) to ensure reliability for life safety and critical operations.
Specifies requirements for the installation, testing, and maintenance of emergency and standby power systems for life safety and essential services.
Quick Reference — Top IS 15228:2002 Values
Key parameters for EPS classification, installation clearances, fuel supply, ventilation, and testing acceptance criteria.
✓ Verified 2026-04-27
Reference
Value
Clause
EPS Class 0 Transfer Time— For Uninterruptible Power Supply (UPS) systems.
0 seconds
Cl. 3.2.1
EPS Class 1 Transfer Time— For critical applications requiring very fast transfer.
≤ 1 second
Cl. 3.2.2
EPS Class 10 Transfer Time— Standard for most life safety and critical systems.
≤ 10 seconds
Cl. 3.2.3
EPS Class X Transfer Time— For manually started or non-critical standby systems.
> 10 seconds
Cl. 3.2.4
Min. On-site Fuel Supply— At full rated load, unless otherwise specified.
2 hours
Cl. 5.4.1
Min. Clearance (Non-walkable side)— For maintenance access around the EPS.
0.75 m
Cl. 5.1.3
Min. Clearance (Walkable side)— For maintenance access and personnel movement.
1.0 m
Cl. 5.1.3
Ventilation Air (Combustion)— For naturally aspirated engines.
0.0028 m³/s per kW
Cl. 5.2.2.1
Ventilation Air (Cooling)— For radiator cooled sets. Varies with manufacturer.
0.09 m³/s per kW
Cl. 5.2.2.2
Initial Acceptance Test Duration— At full rated load after temperature stabilization.
2 hours
Cl. 6.2.2
Voltage Drop (Load Application)— Of rated voltage, for an instant.
≤ 15 %
Cl. 6.2.3.1
Frequency Drop (Load Application)— Below rated frequency.
≤ 5 Hz
Cl. 6.2.3.1
Voltage Recovery Time— To within ±1% of rated voltage.
≤ 1.5 seconds
Cl. 6.2.3.1
Frequency Recovery Time— To within ±0.5% of rated frequency.
≤ 5 seconds
Cl. 6.2.3.1
Steady State Voltage Regulation— From no load to full load.
± 1 %
Cl. 6.2.3.1
Steady State Frequency Regulation— From no load to full load.
± 0.5 %
Cl. 6.2.3.1
Weekly Operational Test— After reaching normal operating temperature.
5 min (no-load)
Cl. 6.3.2.1
Monthly Operational Test— Using building load or a load bank.
30 min at ≥ 30% load
Cl. 6.3.2.2
Battery Charger Capability— After a full discharge from cranking.
Recharge in ≤ 24 hours
Cl. 5.7.4.2
Engine Oil Level Check— Part of routine maintenance schedule.
Weekly
Table 1
Coolant Level Check— Part of routine maintenance schedule.
Weekly
Table 1
⚠ Verify against the latest BIS/IRC publication and project specifications. Amendment Slips may modify values.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! The classification of the system into Level, Class, and Type is the most critical first step, as it dictates all subsequent design and testing parameters.
! Regular on-load testing using a load bank is crucial to verify that the generator set can perform under actual emergency conditions, a step that is often overlooked.
! Ensure strict adherence to installation guidelines for ventilation, exhaust routing, and fuel storage to prevent safety hazards like overheating and fume accumulation.
diesel generator setsbatteriesUPSautomatic transfer switchcablesswitchgear
International Equivalents
Similar International Standards
NFPA 110-2022NFPA (US)
HighCurrent
Standard for Emergency and Standby Power Systems
Covers performance requirements for emergency and standby power systems providing an alternate source of electrical power.
ISO 8528-12:1997ISO (International)
MediumCurrent
Reciprocating internal combustion engine driven alternating current generating sets — Part 12: Emergency power supply to safety services
Focuses on the generating set and its specific application requirements for powering emergency safety services.
IEC 60364-5-56:2018IEC (International)
MediumCurrent
Low-voltage electrical installations - Part 5-56: Selection and erection of electrical equipment - Safety services
Specifies requirements for the overall electrical installation of safety services, including the choice of power source.
BS EN 50171:2021BSI (UK) / CENELEC (EU)
LowCurrent
Central power supply systems
Details requirements for central power systems, often battery-based (like UPS), intended to supply essential safety equipment.
Key Differences
≠NFPA 110 uses a detailed classification system of 'Level' (criticality), 'Class' (runtime in hours), and 'Type' (transfer time in seconds) to define system performance. IS 15228 is less prescriptive, providing general guidance without this formal classification framework.
≠NFPA 110 has highly specific on-site fuel storage requirements tied to its 'Class' rating (e.g., Class 48 requires 48 hours of fuel). IS 15228 provides a general recommendation for a minimum of 8 hours of fuel, which is significantly less stringent for critical facilities.
≠Weekly testing in NFPA 110 for Level 1 systems requires a 'no-load' test, whereas the monthly test mandates running under a specified minimum load (e.g., 30% of nameplate). IS 15228 combines these, recommending a weekly 'no-load' run and a monthly test on 'available building load' for at least an hour, which may not meet a minimum percentage threshold.
≠NFPA 110 is more comprehensive in its scope, providing detailed requirements for ancillary systems such as remote annunciation panels for Level 1 systems, specific temperature maintenance for generator rooms in cold climates, and seismic anchoring, which are not explicitly detailed in IS 15228.
Key Similarities
≈Both standards cover the same core components of an emergency power supply system: the prime mover/generator, fuel system, cooling and exhaust systems, starting equipment (batteries), and transfer switches.
≈Both mandate the use of automatic transfer switches (ATS) for critical applications to ensure an seamless and automatic transition from the normal power source to the emergency source upon failure.
≈Both standards emphasize the importance of locating the generator set in a dedicated, well-ventilated room, separate from other equipment and protected from environmental risks like fire and flooding.
≈Both IS 15228 and NFPA 110 require the implementation of a regular schedule for inspection, testing, and maintenance, and stress the necessity of maintaining detailed written records of all activities and test results.
≈Both codes specify a time-delay for engine cooldown, requiring the generator to run on no-load for a minimum period (typically 5 minutes) after the normal power is restored and before the engine shuts down.
Parameter Comparison
Parameter
IS Value
International
Source
Transfer Time (Critical Systems)
Generally within 15 seconds (Clause 6.2.2)
10 seconds (for Type 10 systems)
NFPA 110-2022
Minimum On-site Fuel Storage
Sufficient for 8 hours continuous running at full rated load (Clause 5.4.1)
Varies based on 'Class' rating (e.g., Class 2 = 2 hours, Class 48 = 48 hours)
NFPA 110-2022
Monthly Load Test Duration
At least 1 hour on available building load (Clause 9.3.2.1 c)
At least 30 minutes at >=30% of nameplate rating (for diesel)
NFPA 110-2022
Engine Cooldown Period
Minimum 5 minutes run on no-load before shutdown (Clause 6.3.3)
Minimum 5 minutes (for Level 1 systems)
NFPA 110-2022
Ventilation Airflow
General guidance to maintain temp below 40°C and provide combustion air (Clause 5.2.2)
Specific design calculations required to limit max temp rise over ambient and provide required combustion air based on engine data
NFPA 110-2022
Battery Charger Type
Automatic, float-cum-boost type (Clause 5.5.3)
Automatic, float-type charger with alarms for high/low voltage and charger failure (for Level 1)
NFPA 110-2022
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
EPSS Level 1 CriticalitySystems where failure could result in loss of life or serious injuries.
EPSS Class 10 Transfer TimeMaximum 10 seconds to switch to emergency power.
EPSS Class 0 Transfer TimeNo interruption in power supply (UPS or equivalent).
EPSS Type 2 Fuel DurationMinimum 2 hours of fuel supply at rated load.
Weekly Test Minimum Duration30 minutes run time for the generator set.
Tables & Referenced Sections
Key Tables
Table 1 - EPSS Level
Table 2 - EPSS Class
Table 3 - EPSS Type
Table 4 - Routine Test and Inspection Schedule
Key Clauses
Clause 4 - Classification of Emergency Power Supply Systems (EPSS)
Clause 6 - Installation and Environmental Considerations
It signifies that the emergency power system must be able to detect the normal power loss and supply power to the load within a maximum of 10 seconds (Table 2).
What is the difference between EPSS Level 1 and Level 2?+
Level 1 is for systems where failure could cause loss of life or serious injury (e.g., life support in hospitals). Level 2 is for less critical systems where failure might lead to public inconvenience or economic loss (Table 1).
How often should a generator be tested?+
It should be inspected weekly and tested by running for at least 30 minutes. A monthly on-load test is also required to bring the prime mover to its operating temperature (Table 4).
What is an EPSS 'Type'?+
Type defines the minimum duration for which the emergency power system must supply power at its rated load, e.g., Type 2 means 2 hours, Type 48 means 48 hours (Table 3).