Frequently Asked Questions
Sizing
Start with a load study, not a rule of thumb. List the connected load, identify which of it must run on backup, and establish the starting characteristics of the largest motors, since motor starting current can be several times running current. Add headroom for future load. The result is stated in kW, then converted to kVA using the power factor to arrive at the set rating. Undersizing causes voltage and frequency dips on load acceptance. Oversizing causes long-term running at low load factor, which damages the engine.
kVA is apparent power, kW is real power, and kW equals kVA multiplied by the power factor. At a 0.8 power factor, a 100 kVA generator delivers 80 kW. Gensets are sold and specified in kVA, but building loads are usually stated in kW, so the conversion has to be done deliberately rather than assumed.
It depends on the load profile and the redundancy required. A single set is simpler and cheaper to install. Multiple sets sharing load through a synchronising panel let you run closer to efficient load factor when demand is low, and they keep supply available when one set is out for maintenance. Data centres, hospitals, hotels and large commercial developments usually justify multiple sets. A single standby set is normally sufficient for smaller commercial buildings.
Fuel and Storage
Very likely, if you are installing a bulk tank. High speed diesel is a petroleum Class B product. The Petroleum and Explosives Safety Organisation's published position is that no licence is required where the quantity in possession does not exceed 2,500 litres in drums, or 1,000 litres in a receptacle or tank. Most commercial and industrial installations with a bulk storage tank exceed 1,000 litres and fall inside the licensing regime under the Petroleum Rules 2002.
No. That threshold applies to petroleum Class C, which covers furnace oil and LDO. Class C is exempt from licensing up to 45,000 litres in bulk but requires a prior report under rule 140 of the Petroleum Rules 2002 above 5,000 litres. Diesel is Class B and carries a far lower threshold. The 5,000 litre figure is widely repeated in relation to diesel and is incorrect.
Compliance
It depends on the capacity of the installation and the threshold notified by your state government. Regulation 34 of the CEA (Measures relating to Safety and Electric Supply) Regulations 2023 provides that the capacity above which generating units must be inspected by the Electrical Inspector before commissioning is fixed by notification of the Appropriate Government, rather than by a single national figure. Regulations 32 and 45 allow self-certification at or below the voltage notified by the state, with the report submitted to the Electrical Inspector's office. Note that the 2023 Regulations superseded the 2010 Regulations of the same name on 8 June 2023, and the regulation numbers changed. Confirm the position for your specific installation and location.
CPCB IV+ is the emission standard notified vide GSR 804(E) dated 3 November 2022, applying to internal combustion engines used in generating sets up to 800 kW gross mechanical power. It replaced the earlier CPCB II norms. If you are buying a new genset within that power range, it applies. No genset containing an engine may be sold, imported or used in India without a valid Type Approval Certificate and Conformity of Production Certificate.
Two, before the purchase order is raised. A Type Approval Certificate, confirming the engine type meets the applicable emission limits, and a Conformity of Production Certificate, confirming production units continue to meet the standard the type was approved against. Both are issued by CPCB-approved agencies: ARAI Pune, ICAT Manesar and the Indian Institute of Petroleum, Dehradun. The COP certificate is issued per COP year, which runs 1 July to 30 June, so check it covers the current year.
Consent for Establishment before the installation is built, and Consent for Operation before it runs, both granted by the State Pollution Control Board under the Water Act 1974 and the Air Act 1981. The Consent for Operation is issued after the board inspects the completed installation. Consent orders list each DG set as an emission source, specify a minimum chimney height above ground level, and require an acoustic enclosure as the noise control measure.
The owner. Under Regulation 5 of the CEA Safety Regulations 2023, every electrical installation with more than 250 kW of connected load must have a designated Electrical Safety Officer, qualified as an electrical engineering degree holder with at least five years of operation and maintenance experience, or a diploma holder with at least ten years. That officer must inspect the installation at intervals not exceeding one year and keep records available to the Electrical Inspector. Regulation 32 separately requires periodic inspection and testing at intervals not exceeding five years.
Noise
Two limits apply. Under GSR 371(E), new diesel generator sets up to 1000 kVA are limited to 75 dB(A) measured at 1 metre from the enclosure surface, with an integral acoustic enclosure fitted at the manufacturing stage. Separately, where a set is not covered by that provision, CPCB requires the acoustic enclosure or room treatment to be designed for a minimum 25 dB(A) insertion loss, or to meet ambient noise standards, whichever is higher.
The user, not the manufacturer. CPCB places the obligation to bring noise levels outside the premises within ambient noise requirements on the user, through siting and control measures. Ambient limits under the Noise Pollution (Regulation and Control) Rules 2000 are 75 dB(A) Leq by day and 70 at night in industrial areas, 65 and 55 in commercial areas, 55 and 45 in residential areas, and 50 and 40 in silence zones, where day means 6 am to 10 pm. A set that met 75 dB(A) at the factory can still breach the residential limit at a boundary.
Maintenance
Preventive maintenance runs to the OEM schedule rather than a fixed calendar. Across the Mahindra Powerol range the lube oil change period is 500 hours, and the overhaul period extends up to 15,000 hours. Standby sets that run only occasionally still need scheduled attention, because batteries, coolant and fuel degrade whether the engine runs or not. Escon offers monthly, bi-monthly and quarterly visit schedules depending on the contract.
It depends on the package. A Basic AMC covers monthly checks, preventive maintenance, inspection, cleaning, performance checks and service reports, with consumables and spare parts charged separately. A Comprehensive AMC adds breakdown support, labour, lubricants, filters, routine consumables and covered spare parts as agreed. A Customized AMC tailors coverage to the site, including 24x7 support, remote locations, critical applications and annual overhauls. Escon's service commitments include 24x7 emergency breakdown support for critical customers, breakdown response within 4 hours, commissioning calls within 48 hours, genuine spares and lubricants, and a digital service report after every visit.
Vendor Selection and Timelines
One vendor removes the interface risk. On a split contract the genset supplier, the electrical contractor, the fabricator and the acoustic vendor each design to their own scope, and the gaps between those scopes are found on site rather than on paper. A turnkey contract puts supply, installation, acoustic treatment, statutory approvals and commissioning under one project manager accountable for the commissioning date. Split contracts can work where the buyer has a strong in-house projects team to coordinate them.
Acoustic Guide
No, and comparing them directly is a common specification error. Sound power level is a property of the machine and does not vary with distance. Sound pressure level is what a meter reads at a given point and falls with distance. The 75 dB(A) statutory limit is a sound pressure level at 1 metre. Type testing measures sound power level per ISO 3744 and ISO 8528-10. When comparing supplier datasheets, confirm which quantity is quoted and at what distance.
Not where the exhaust is ducted away to a remote discharge point. The scope of ISO 8528-10 excludes the noise contribution of exhaust and cooling systems ducted to a remote site, so a set's certified figure does not account for what leaves a stack at roof level. Exhaust noise is controlled separately, through a silencer carrying its own minimum 25 dB(A) insertion loss requirement.
Insertion loss is the reduction in sound level achieved by adding an enclosure, room treatment or muffler. CPCB requires enclosures and room treatment to be designed for a minimum of 25 dB(A), or for the applicable ambient standard, whichever is higher. It is a design requirement, so the specification has to be established before manufacture rather than tested for afterwards.
It can, if the ventilation path is restricted rather than treated. Diesel engines need airflow for combustion and cooling, and narrowing the intake or discharge to reduce noise raises operating temperature and derates the set. Properly designed treatment lengthens and lines the airflow path using baffled inlets and outlets instead of restricting it.
An enclosure where the set can practically be canopied, room treatment where it cannot. Multiple sets in one plant room, higher-rated sets and sets already installed open usually call for room treatment. The engineering principles are identical, the difference is scale.
Usually, though the options narrow. Room treatment can be applied to a built DG room, and enclosures can be added to open sets. What cannot easily be changed after the fact is the ventilation opening and the siting of the set, which is why the retrofit result is often more expensive and less effective than designing for the target at the start.
Why Turnkey
On a turnkey contract, the contractor, since they produced the drawings, executed the work and submitted for approval. On a split contract it depends on why it failed, and that is the problem. A failure caused by earthing sits with the electrical contractor, one caused by clearance around the switchboard may sit with the civil contractor or the designer, and one caused by chimney height sits between the structural and consent scopes. Establish in advance who is accountable for approval as an outcome, not just for their own workmanship.
Yes, and many buyers do. The risk is not the split itself but the specification gap. The genset supplier specifies airflow, backpressure limits and foundation loading. Those requirements have to reach the installation tender in enough detail to be priced and built to. Where the supply order is placed first and the installation tendered later against a generic scope, the installer prices what is written rather than what the set needs.
On the contract value, often yes, since coordination is priced in rather than absorbed by the buyer. On total cost, it depends entirely on whether the buyer would have absorbed that coordination well. The costs that do not appear in either tender are programme delay, derating from a badly sized ventilation opening, and rework after a boundary noise complaint. Those are the costs a split contract exposes the buyer to and a turnkey contract prices against.
That is a common and workable position. Scope the turnkey contractor for supply, acoustics, exhaust, fuel and approvals, and carve out the electrical works, but define the interface explicitly. Name who terminates at the panel, who tests and issues the megger and earthing reports, and who is accountable for the installation passing inspection. A carve-out with a defined interface behaves like a turnkey contract. A carve-out without one behaves like a split contract with extra steps.
Rent or Buy with an AMC
Over a short period, almost always. Over a permanent requirement, almost never. The crossover depends on the rental rate, the capital cost of an equivalent set, installation cost and your cost of capital, so it is worth calculating for your specific case rather than assuming. Rental also transfers the maintenance and statutory burden, which has value beyond the rate itself.
No. Escon supplies, installs and maintains diesel generator sets, and manufactures acoustic enclosures. It does not operate a rental fleet. Where a requirement is genuinely temporary, rental is the right answer and a rental provider is the right supplier.
Usually yes, and the reasoning is counterintuitive. A standby set that rarely runs still degrades. Batteries lose charge, coolant and fuel deteriorate, and seals dry out. The failures that matter on standby sets are typically failures to start rather than failures under load, and those are exactly what scheduled inspection catches. A quarterly or bi-monthly package is often the right level for a lightly used set.
Coverage of parts and labour on breakdowns. Basic covers scheduled preventive maintenance, inspection and reporting, with consumables and spare parts charged separately as used. Comprehensive adds breakdown support, labour, lubricants, filters, routine consumables and covered spare parts within the agreement. Basic gives a lower fixed cost with variable exposure. Comprehensive gives a higher fixed cost with less variability. Which is better depends on how predictable your duty cycle is.
It depends on the OEM's warranty terms, which typically require maintenance to the published schedule using genuine parts, with records kept. Self-maintenance is compatible with that if the schedule is followed and documented. The risk is not the decision to self-maintain, it is undocumented or delayed servicing, which is the common reason claims are challenged.
Sources
Ministry of Environment and Forests, GSR 371(E) dated 17 May 2002, as recited in MoEF correspondence on noise and emission limits for generator sets. Central Pollution Control Board, System and Procedure for Compliance to Emission and Noise Limits for Gensets, 2016, clause 4.3. Noise Pollution (Regulation and Control) Rules, 2000, as applied in Karnataka State Pollution Control Board Consent for Operation orders. Automotive Research Association of India, genset certification, noise testing at the NVH Laboratory. ISO 8528-10, adopted in India as IS/ISO 8528-10 by the Bureau of Indian Standards. ISO 3744 and ISO 3746. ISO 15619 for exhaust silencer insertion loss. Mahindra Powerol published enclosure specifications
Central Pollution Control Board, System and Procedure for Compliance to Emission and Noise Limits for Gensets, clause 4.3. Ministry of Environment and Forests, GSR 371(E). Central Electricity Authority (Measures relating to Safety and Electric Supply) Regulations, 2023. Petroleum and Explosives Safety Organisation, published FAQs on the Petroleum Rules 2002. ISO 8528-10 published scope. Karnataka State Pollution Control Board Consent for Operation orders.
Central Electricity Authority (Measures relating to Safety and Electric Supply) Regulations, 2023, regulations 5 and 32. Mahindra Powerol published service intervals and range specifications. Escon Gensets service operations profile.