Quick Reference of Diesel Generator Set-(Part-1)


Standard Size of The DG sets

7.5 KVA20KVA35 KVA62.5 KVA100 KVA
10 KVA25 KVA40 KVA75 KVA125 KVA
15 KVA30 KVA50 KVA82.5 KVA200 KVA


Bar Size for D.G Foundation

Rating of D.G setSize of Bar
Up to 82.5 KVA10MM
100 KVA To 200 KVA12MM
250 KVA to 500KVA16MM


Minimum Capacity of Daily Fuel Service Tank  (AS per CPWD)

Capacity of DG setMinimum Fuel Tank Capacity
Upto 25 KVA100 Litres
Above 25 to 62.5 KVA120 Litres
Above 62.5 KVA to 125 KVA225 Litres
Above 125 KVA to 200 KVA285 Litres
Above 200 KVA to 380 KVA500 Litres
Above 380 KVA to 500 KVA700 Litres
Above 500 KVA to 750 KVA900 Litres


Battery Size for D.G Set  (AS per CPWD)

DG Set CapacityBattery Capacity (AH)Cu Cable Size (Sq. mm)Electrical System (Volts)
Upto 25 KVA883512
Above 25 KVA upto 62.5 KVA1205012
Above 62.5 KVA upto 82.5 KVA1505012
Above 82.5.KVA upto 125 KVA1805012
Above 125 KVA upto 500 KVA1807012
Above 500 KVA3607024


Depths of PCC (Plain Cement Concrete)  for DG Set (As per CPWD)
DG Set Capacity (KVA)Typical Depth of PCC Foundation (For soil bearing capacity 5000 kg/sqm)
750-2000600 mm
625400 mm
320-500400 mm
200-320400 mm
82.5 -200400 mm
Upto 82.5200 mm


Area Required For Generator in Electrical Sub Station (As per NBC)

Capacity  kVAArea m2Clear Height below the Soffit of the Beam m



Starting Current for D.G set

Type of LoadStarting Current
Motors over 50 HP6 X motor rated current
Variable frequency drive motors2 X motor rated current
Uninterruptible power supply (UPS) loads1.5 X UPS rated current
Battery charger loads2.5 X Charger rated current
Non-Linear Load1.5 to 2.5 X rated current
Medical imaging loads1.1 X Rated current
Soft Starter Motor1.2 X motor rated current
DOL Starter4 X motor rated current
Star-Delta Starter3 X motor rated current
Auto Transformer Starter1.5 X motor rated current
Most generators are capable of delivering 300% of the rated current for 10 seconds



Stand by D.G Permission As per PSEB

D.G Set CapacityPermissionRemarks
Up to 10 KW(11 KVA)No permission is required. Also prior sanction of CEI is not required. 
10 KW (11 KVA) to 250 KVA
250 KVA to 1 MVA
1 MVA to 2.5 MVAPermission is required. Also prior sanction of CEI is requiredThe capacity of D.G Set should not exceed 1.2 times of the sanctioned Load.
2.5 MVA to 5 MVA
Exceeding 5 MVA


Sound Level of Diesel Generator (ANSI 89.2&NEMA 51.20):

KVAMax. Sound Level
<9 KVA40 DB
10 KVA to 50 KVA45 DB
51 KVA to 150 KVA50 DB
151 KVA to 300 KVA55 DB
301 KVA to 500 KVA60 DB


Exhaust Stack Height

Up to 1000KVA D.GTotal Height of stack (Meter) = (Height of Building Where D.G Installed +0.2 ) X √D.G Capacity in KVA
More than 1000KVA D.G30 Meter height or more than 3 meter height of building which is higher.


Height of stack (Meter)

Generator SetsTotal Height of Stack in Meters.
000 to 050 KVAHeight of Building + 1.5 Meter
050 to 100 KVAHeight of Building + 2.0 Meter.
100 to 150 KVAHeight of Building + 2.5 Meter
150 to 200 KVAHeight of Building + 3.0 Meter
200 to 250 KVAHeight of Building + 3.5 Meter
250 to 300 KVAHeight of Building + 4.0 Meter.


D.G Room Air Requirement

D.G SetAir Requirement
275 KVA605 Cu. Meter / Min
320 KVA625 Cu. Meter / Min
400 KVA854 Cu. Meter / Min
500 KVA1065 Cu. Meter / Min
600 KVA1286 Cu. Meter / Min


Noise Limit of D.G Set As per CPWD, India

Up to 1000 KVA (manufactured after 2005) =75 dB(A) at 1 meter from the enclosure surface
The acoustic enclosure or acoustic treatment of the room shall be designed for minimum 25 dB(A) insertion loss or for meeting the ambient noise standards, whichever is on the higher side.
The measurement for insertion loss may be done at different points at 0.5 m from the acoustic enclosure / room, and then averaged.
The DG set shall be provided with proper exhaust muffler with insertion loss of minimum 25 dB(A).


Foundation & Earthing for D.G Set  (As Per CPWD)

D.G set inside RoomA PCC foundation (1:2:4, M-20 grade) of approximate depth 150 mm above the finished Genset Room Floor level
The  length  and  breadth  of  foundation  should  be  at  least  250  mm   more on all sides than the size of the enclosure.
D.G set in Open RoomA PCC (1:2:4, M-20 grade) foundation  of  weight  2.5  times  the  operating  weight  of  the  Genset  with  enclosure  or  as recommended by the Genset manufacturer, whichever is higher
300 mm of this foundation height should be above the ground level. The length and breadth of foundation should be at least 250 mm more on all sides than the size of enclosure.
EarthingCopper plate earthing (Neutral Grounding) shall be provided for DG Sets of capacity 500 KVA or above
whereas G.I. plate earthing (Neutral Grounding) shall be provided for DG Sets below 500 KVA capacity. The body earthing shall generally be of G.I
Numbers of earthing for each DG Sets2No’s  earthing sets for Genset/ control panel body.
2No’s earthing sets for neutral.
In case there are more than one DG Set in one location, independent two nos. neutral earthing shall be provided for each DG set. However, two nos. earthing sets shall be common for the body earthing of DG Sets
DG Set of 500 KVA capacity or above:- Copper strip
DG Set below 500 KVA capacity:- GI strip


D.G Spacing Guidance

DescriptionDG set with Acoustic EnclosureOpen DG set in room.
in Open Areain Closed Area
Free space on both sidesMin. 1.5 mMin. 1.5 mMin. 2 m
Free space at front side (Radiator Hot air outlet at Front)Min. 3 mMin. 3 mN/A
Free space at front side (Radiator Hot air outlet at Top)Min. 1.0 mMin. 1.5 mN/A
Free space at rear side
Min. 2 mMin. 2 mMin. 2 m
Fresh air inlet opening areaN/AN/AMin 1.5 times of the Radiator area.
Hot air discharge opening areaN/AN/AMin 2.5 times of the Radiator area.
Distance between two setsMin 1.5m between two
Min 1.5m between
two canopies
Min 1.5m between two foundations.


D.G Detail according to Size

D.G Size (KVA)L x W x H (Canopy) mmApprox Weight (Kg)Fuel Tank (Ltrs)Fuel Consumption (Ltr/hr)Oil Consumption (Ltr/hr)
12.52040 x 1230 x 14501050602.30.02
152040 x 1230 x 14501050652.30.02
202240 x 1230 x 14501300653.70.03
302510 x 1130 x 14501300656.30.03
403350 x 1180 x 165015001007.80.03
503350 x 1180 x 165015001008.30.03
62.53350 x 1180 x 1650193015010.50.03
753605 x 1405 x 16001950150130.03
1003940 x 1700 x 1850250030015.70.05
1253950 x 1700 x 18502700300190.05
1404600 x 1850 x 1950358030022.60.06
1604600 x 1850 x 1950372045025.90.14
1804970 x 1730 x 2045387045027.70.14
2004970 x 1730 x 2045395045029.80.14
2504970 x 1730 x 2050466045037.70.15
2755700 x 2030 x 25155860450500.15
3205700 x 2030 x 25155860450570.3
4005905 x 2030 x 2520618099065.10.3
5006205 x 2030 x 2550699099081.30.3