Thumb Rules-14 ( Quick Reference Demand-Diversity Factor)


 

Diversity Factor (NBC)

Type of Load

Type of Building

Individual House Hold , Individual Dwelling of a Block Small Shops, Stores, Offices & Business Premises Small Hotels, Boarding Houses, etc
Lighting 66% of  total current demand 90% of total current demand 75% of total current demand
Heating and power 100% of total current demand up to 10 A+ 50 % of any current  demand in excess of 10 A 100% of full load of largest Appliance + 75% of Remaining appliances 100% of full load of largest appliance+ 80% of second largest appliance + 60% of remaining appliances
Cooking appliances 10 A +30 percent full load of
connected cooking appliances in excess of 10 A + 6 A if socket-outlet incorporated in the unit
100 % of full load of largest appliance + 80% of full load of second largest appliance + 60% of full load of Remaining appliances 100 % of full load of largest appliance + 80 % of full load of second largest appliance + 60% of full load of Remaining appliances
Motors (other than lift motors which are subject to special consideration)   100% of full load of largest Motor + 80% of full load of second largest motor 100 % of full load of largest Motor + 50%of full load of remaining motors
Water heater (instantaneous) 100 % of full load of largest Appliance + 100%of full load of second largest appliance + 25 %of full load of remaining appliances 100 % of full load of largest Appliance + 100%of full load of second largest appliance + 25 %of full load of remaining appliances 100 % of full load of largest Appliance + 100%of full load of second largest appliance + 25 %of full load of remaining appliances
Water heater (thermostatically controlled) No diversity    
Standard arrangements of final circuits in accordance with good practice 100 percent of the current demand of the largest circuit + 40 percent of the current demand of every other circuit 100 percent of the current
demand of the largest circuit + 50 percent of the current demand of every other circuit
 
Socket outlets other than above and stationary equipment other than those listed above 100% of the current demand of the largest point + 40%of the current demand of every other point 100% of the current
demand of the largest point+ 75 % of the current demand of every other point
100%of the current demand of the largest point
+ 75%of the current demand of every point in main rooms (dining rooms, etc) + 40 % of the current demand of every other point
After calculating the electrical load on the above basis, an overall load factor of 70 to 90 percent is to be applied to arrive at the minimum capacity of substation.

 

Demand Factors (As Per Table 220.42  NEC)

Type of Occupancy Electrical Load Demand Factor
Dwelling units First 3000 VA 100%
From 3001 to 120,000 VA 35%
Remainder over 120,000V A 25%
Hospitals First 50,000 VA or less 40%
Remainder over 50,000 VA 20%
Hotels and motels, including apartment houses without provision for cooking by tenants First 20,000 VA 50%
20,001 VA to 100,000 VA 40%
Remainder over 100,000 VA 30%
Warehouses storage First 12,500 VA 100%
Remainder over 12,500 VA 50%
All others Total volt-ampere 100%

 

Non-dwelling Lighting Loads Demand Factors (As Per 220.44  NEC)

Type of Occupancy Electrical Load Demand Factor
Non-dwelling Receptacle Loads First 10KVA 100%
Remainder over 10KVA 50%

 

Diversity (The Electricians Guide 5th Edition by John Whitfield)

Type of final circuit Type of premises
Households Small shops, stores, offices Hotels, guest houses
Lighting 66% total demand 90% total demand 75% total demand
Heating and power 100% up to 10 A + 50% balance 100%X + 75%(Y+Z) 100%X + 80%Y + 60%Z
Cookers 10 A + 30% balance + 5 A for socket 100%X + 80%Y + 60%Z 100%X + 80%Y + 60%Z
Motors (but not lifts)   100%X + 80%Y + 60%Z 100%X + 50%(Y+Z)
Instantaneous water heaters 100%X + 100%Y + 25%Z 100%X + 100%Y + 25%Z 100%X + 100%Y + 25%Z
Thermostatic water heaters 100% 100% 100%
Floor warming installations 100% 100% 100%
Thermal storage heating 100% 100% 100%
Standard circuits 100%X + 40%(Y+Z) 100%X + 50%(Y+Z) 100%X + 50%(Y+Z)
Sockets and stationary equip. 100%X + 40%(Y+Z) 100%X + 75%(Y+Z) 100%X + 75%Y + 40%Z
X = the full load current of the largest appliance or circuit
Y = the full load current of the second largest appliance or circuit
Z = the full load current of the remaining appliances or circuits

 

Diversity factor for Building (Horizon Power)

No of customer Diversity factor
1 3
2 2.57
3 2.2
4 2
5 1.89
6 1.8
7 1.74
8 1.71
9 1.69
10 1.64
11 1.61
12 To 14 1.57
15 To 17 1.5
18 To 20 1.46
21 To 23 1.42
24 to 26 1.4
27 To 29 1.38
30 To 59 1.37
≥60 1

 

Demand Factor (The Electricians Guide Fifth Edition) by John Whitfield)

Area Demand Factor
Office / School 40%
Technical Blocks / Hospital 50%
Air Port / Banks / Department Store / Shopping Center / Public Place 60%
Restaurants / Factories (for 8 Hours Shifts) 70%
Workshops / Factories (for 24 Hours Shifts) 80%
Arc Furnace 90 % TO 100%
Arc Welding 20 % TO 50%
Compressor 20 % TO 50%
Conveyor Crane 90 % TO 100%
Had tool 20 % TO 40%
Paper Mills 50 % TO 70%
Induction Furnace 80 % TO 100%

 

Demand Factor As per No of Appliances

No of Appliances (A) Less than 3.5 KW (B) 3.5 KW to 8.5 KW (C) Less 12 KW
1 80% 80% 8%
2 75% 655 11%
3 70% 55% 14%
4 66% 50% 17%
5 62% 45% 20%
6 59% 43% 21%
7 56% 36% 22%
8 53% 35% 23%
9 51% 34% 24%
10 49% 32% 25%
11 47% 32% 26%
12 45% 32% 27%
13 43% 32% 28%
14 41% 32% 29%
15 40% 32% 30%
16 39% 28% 31%
17 38% 28% 32%
18 37% 28% 33%
19 36% 28% 34%
20 35% 28% 35%
21 34% 26% 36%
22 33% 26% 37%
23 325 26% 38%
24 31% 26% 39%
25 30% 26% 40%
26 To 30 30% 24% 15KW+1KW for Each
31 To 40 30% 22%
41 To 50 30% 20% 25KW+0.75KW for Each

 

51 To 60 30% 18%
More Than 60 30% 16%
       

 

Lighting Demand for Building (As per NBC)

Lighting demand for buildings should be considered as per type of building.
Where nothing is specified, for lighting demand of any type of building a maximum of 13 W/m2 of all built-up areas including balconies.
Covered parking areas may be considered at 3.23 W/m2 including balconies, service areas, corridors, etc, may be considered with very basic diversity of 80 % to 100 %.
Power requirements shall be considered at least 55 W/m2 with an overall diversity not exceeding 50 %. These shall be excluding defined loads such as  lifts,  plumbing  system,  fire  fighting  systems, ventilation requirement, etc.
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Thumb Rules-13 ( Quick Reference Earthing -CPWD)


 

Earthing Strip for Sub-Station Equipment

CPWD-TABLE VIII

Type of Installation Earth Electrode Earth Strip
Indoor sub-station with HT panel, Transformer capacity up to  1600  KVA, LT panel, D.G Set. Copper Plate 25 x 5 mm Copper Strip
Indoor sub-station with HT  panel, Transformer  capacity  above  1600  KVA, LT panel, D.G Set Copper Plate 32 x 5 mm Copper Strip
HT Outdoor sub-station Copper Plate 25 x 5 mm Copper Strip
LT Indoor sub-station with generator Copper Plate 25 x 5 mm Copper Strip
LT   switch   room   with Main   LT  D.B Copper Plate 20 x 3 mm Copper Strip

 

Neutral Earthing of Transformers and Generators

CPWD-TABLE VIII

Type of Installation Earth Electrode Earth Strip for Neutral
Transformer  of  capacity  up  to  1600 KVA Copper Plate 25 x 5 mm Copper strip
Transformer  of  capacity  above  1600  KVA Copper Plate 32 x 5 mm Copper strip
Generating set of all capacity Copper Plate 26 x 5 mm Copper strip
Type of Installation Earth Electrode Earth Strip for Neutral
Transformer  of  capacity  up  to  1600 KVA Copper Plate 25 x 5 mm Copper strip

 

Earthing Strip for Bus Trunking and Rising Main

CPWD-TABLE VIII

Type of Installation Material of Main Conductor Earth Strip
Bus   trunking   up   to   2500   Amp   capacity Copper/ Aluminum 2 No 25 x 5 mm Copper Strip
Bus   trunking   above   2500   Amp   capacity Copper/ Aluminum 2 No 32 x 5 mm Copper Strip
Bus  trunking for  generating set and LT panel Copper/ Aluminum 2 No 25 x 5 mm Copper Strip
Rising main up to 400 Amp capacity Copper/ Aluminum 2 No 20 x 5 mm Copper Strip
Rising  main  above  400  Amp  and  up to 800 Amp Copper/ Aluminum 2 No  20 x 3 mm Copper Strip

 

The Size of Earthing conductors

As per CPWD

Size of phase conductor Size of Earthing conductor of the same material as phase conductor
Up to 4 sq.mm. Same size as that of phase conductor
Above 4 sq.mm. up to 16 sq.mm. Same size as that of phase conductor
Above 16 sq.mm. up to 35 sq.mm. 16 sq.mm.
Above 35 sq.mm. Half of the phase conductor

 

Materials and Sizes of Earth Electrodes

CPWD-TABLE IX

Type of Electrodes Material Size
Pipe GI medium class 40 mm dia 4.50 m long (without any joint)
Plate (i) GI 60 cm x 60 cm x 6 mm thick
(ii) Copper 60 cm x 60 cm x 3 mm thick
Strip (i) GI 100 sq. mm section
(ii) Copper 40 sq. mm section
Conductor (i) Copper 4 mm dia (8 SWG)
Note :  Galvanization of GI items shall conform to Class IV of IS 4736 : 1986.

 

Minimum Sizes of Earthing Conductors for Use Above Ground

CPWD- TABLE X

Material and Shape Minimum Size
Round copper wire or copper clad steel wire 6 mm diameter
Stranded copper wire 50 sq. mm or (7/3.00 mm dia)
Copper strip 20 mm x 3 mm
Galvanized iron strip 20 mm x 3 mm
Round Aluminum wire 8 mm diameter
Aluminum strip 25 mm x 3 mm

 

Minimum Sizes of Earthing Conductors for Use Below Ground

CPWD- TABLE XI

Material and Shape Minimum Size
Round copper wire or copper clad steel wire 8 mm diameter
Copper strip 32 mm x 6 mm
Round galvanized iron wire 10 mm x 6 mm
Galvanized iron strip 32 mm x 6 mm

 

Selection of Type of Earthing Electrodes

As per CPWD

Type of electrode Application
GI pipe Internal electrical installations like Distribution Board and Meter Boards (in residential quarters), feeder pillars and poles etc.
GI plate (i) For Fire Fighting pumps and water supply pumps.
(ii) Lightning conductors.
Copper plate Neutral earthing of transformers/ generating sets.
Strip/ Conductor Locations where it is not possible to use other types.

 

Number of Earth Electrodes

As per CPWD

Equipment No of Earthing
For neutral earthing of each transformer 2 sets
For body earthing of all the transformers, 2 sets
HT/LT Panels and other electrical equipment
in the Sub-station/ power house
For neutral earthing of each generating set 2 sets
For body earthing of all the generating sets, 2 sets
LT panels, other electrical equipment in the generator room

 

Size of protective conductor

As per CPWD

Size of phase conductor Size of protective conductor of the same material as phase conductor
Up to 16 sq.mm. Same as Phase Conductor  Size
16 to 35 sq.mm. 16 sq.mm.
35 sq.mm Half Size of Phase Conductor

 

Earthing Points

As per CPWD

Earthing Description
Location for Earth Electrodes Normally  an  earth  electrode  shall  not  be  located  closer  than  1.5  m  from  any  building.
Installation of Pipe Pipe electrode shall be buried in the ground vertically with its top at not less than 20 cm below the ground level
Installation of Plate Plate electrode shall be buried in ground with its faces vertical, and its top not less than 3.0 m below the ground level.
The strip or conductor The strip or conductor electrode shall be buried in trench not less than 0.5 m  deep
More Earthing Electrode When more than one electrode (plate/pipe) is to be installed, a separation of not less than 2 m shall be maintained between two adjacent electrodes.
Earthing Electrode  If the electrode cannot be laid in a straight length, it may be laid in a zigzag manner with a deviation upto 45 degrees from the axis of the strip. It can also be laid in the form of an arc with curvature more than 1 m or a polygon
Earthing Pit Cover A cast iron / MS frame with MS cover, 6 mm thick, and having locking arrangement shall be suitably embedded in the masonry enclosure.
Earthing Wire Protection  The  earthing  conductor  from  the  electrode  up  to  the  building  shall  be  protected  from mechanical injury by a medium class, 15 mm dia. GI pipe in the case of wire, and by 40 mm dia, medium class GI pipe in the case of strip. The protection pipe in ground shall be buried at least 30 cm deep (to be increased to 60 cm in case of road crossing and pavements)
No of Earthing Conductor Two protective conductors shall be provided for a switchboard carrying a 3-phase switch gear there on.
Earthing Electrode  No earth electrode shall have a greater ohmic resistance than 5 ohms as measured by an approved earth testing apparatus. In rocky soil the resistance may be up to 8 ohms.
Earthing Resistance Each   of   the   earth   stations   should   have   a   resistance   not   exceeding   the product  given  by  10  ohms  multiplied  by  the number  of  earth  electrodes  to be  provided  therein.  The  whole  of  the  lightning  protective  system,  including any  ring  earth, should  have  a  combined  resistance  to  earth  not  exceeding 
10 ohms without taking account of any bonding
More Earthing Resistance If the value obtained for the whole of the lightning protection system exceeds 10 ohms, a reduction can be achieved by extending or adding to the electrodes, or by  interconnecting  the  individual  earth  terminations  of  the  down  conductors  by  a  conductor

 

Calculate Lighting Fixture’s Beam Angle


ScreenHunter_01 Feb. 19 20.59

  • Calculate Lighting Fixture Beam Angle
  • Calculate Illumination at Surface from Beam Angle.
  • Calculate Lighting Fixture Lumen from Beam Angle.
  • Calculate Illuminated Diameter from Beam Angle.

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Calculate Size of Neutral Earthing Transformer (NET)


Calculate Size of Neutral Earthing Transformer (NET) having following details

 Main Transformer Detail :

  • Primary Voltage(PVL): 33KV
  • Secondary Voltage (SVL): 11 KV
  • Frequency(f)=50Hz
  • Transformer Capacitance / Phase(c1)=0.006 µ Farad
  • Transformer Cable Capacitance / Phase(c2)= 0003 µ Farad
  • Surge Arrestor Capacitance / Phase(c3)=0.25 µ Farad
  • Other Capacitance / Phase(c4)=0 µ Farad

Required for Neutral Earthing Transformer:

  • Primary Voltage of the Grounding Transformer (Vp) =11KV
  • Secondary Voltage of the Grounding Transformer (Vs) =240V
  • Neutral Earthing Transformer % Reactance (X%)=40%
  • % of Force field condition for Neutral Earthing Transformer (ff) =30%
  • Neutral Earthing Transformer overloading factor(Of)=2.6
  • Neutral Earthing Transformer Base KV (Bv) =240V=0.240KV

Calculation:

  • Phase to Neutral Voltage (Vp1) =SVL /1.732
  • Phase to Neutral Voltage (Vp1) =11 /1.732 = 6.35 KV
  • Phase to Neutral Voltage under Force Field Condition (Vf) =Vp + (Vpxff)
  • Phase to Neutral Voltage under Force Field Condition (Vf)=6.35+ (6.35×30%) =8.26KV
  • Total Zero Sequence Capacitance (C)=C1+C2+C3+C4
  • Total Zero Sequence Capacitance (C)=0.006+0.0003+0.25+0=0.47730 µ Farad
  • Total Zero Sequence Capacitance Reactance to Ground (Xc)=10×6 / (2×3.14xfxC)
  • Total Zero Sequence Capacitance Reactance to Ground (Xc)=10×6 / (2×3.14x50x0.47730)=6672.35 Ω/Phase
  • Capacitive charging current/phase (Ic)=Vf / Xc
  • Capacitive charging current/phase (Ic)=8.26×1000 / 6672.35 = 1.24Amp
  • Total Capacitive charging current (It) =3xIc
  • Total Capacitive charging current (It) =3xIc =3×1.24 =3.71Amp
  • Rating of Neutral Earthing Transformer (Pr)=VpxIt
  • Rating of Neutral Earthing Transformer (Pr)=11×3.71=40.83KVA
  • Size of Neutral Earthing Transformer (P)=Pr/ Of
  • Size of Neutral Earthing Transformer (P)=40.83/ 2.6 = 16KVA
  • Residual Capacitive reactance (Xct) =Xc/3
  • l Capacitive reactance (Xct) = 6672.35 /3 =2224.12Ω
  • Turns Ratio of the Grounding Transformer (N)= Vp/Vs =11000/240 =45.83
  • Required Grounding Resistor value at Secondary side (Rsec)=Xct/NxN
  • Required Grounding Resistor value at Secondary side (Rsec)=2224.12 /45.83×45.83 =1.059 Ω
  • Required Grounding Resistor value at primary side (Rp)=Xct
  • Grounding Resistor value at primary side (Rp)= 2224.12Ω
  • Neutral Earthing Transformer Secondary Current=P/Vs
  • Neutral Earthing Transformer Secondary Current=16000/230= 65.44Amp
  • Neutral Earthing Transformer Secondary Resistor Current (for 30 Sec)=1.3xItxN
  • Neutral Earthing Transformer Secondary Resistor Current (for 30 Sec)=1.3×3.71×45.83=221.18Amp
  • Neutral Earthing Transformer Reactance Base(Base X)=BvxBv/P/1000
  • Neutral Earthing Transformer Reactance Base(Base X)=0.24×0.24/11/1000=3.67Ω
  • Neutral Earthing Transformer Reactance in PU (Xpu)=X% =40%=0.04Pu
  • Neutral Earthing Transformer Reactance (X)=Xpu x BaseX
  • Neutral Earthing Transformer Reactance (X)=0.04×3.67 =0.15Ω
  • Neutral Earthing Transformer X/R Ratio=X/Rsec
  • Neutral Earthing Transformer X/R Ratio=0.15/1.059 = 0.14
  • Fault current through Neutral (single line to ground fault) (If)=Vp1/Rp
  • Fault current through Neutral (single line to ground fault) (If)=6.35×1000/2224.12 =2.86Amp
  • Short time Rating of Neutral Earthing Transformer=PxOf =16×2.6 =41KVA

Result:

  • Rating of Neutral Earthing Transformer (P)=40.83/ 2.6 = 16KVA
  • Short time Rating of Neutral Earthing Transformer=41KVA
  • Ratio of Neutral Earthing Transformer =11000/240 Volt
  • Neutral Earthing Transformer Secondary Current=65.44A
  • Required Grounding Resistor value at primary side (Rp)=2224.12Ω
  • Required Resistance at secondary side (Rsec)= 1.059Ω
  • Neutral Earthing Transformer Secondary Resistor Current (for 30 Sec)= 221.2A

Calculate Required Air ventilation and Heat generation of D.G Set


Heat Generated by Generator:

  • For generator set installations, the heat radiated by the generator can be estimated by
  • H (kW) =P X ((1/Eff)-1)
  • H (Btu/min) =P X ((1/EFF)-1) x56.9
  • Where:
  • H = Heat Radiated by the Generator (kW), (Btu/min)
  • P = Generator Output at Maximum Engine Rating (kW)
  • Eff = Generator Efficiency % / 100%
  • Example: 975 kW standby generator set has a generator efficiency of 92%. The generator radiant heat for this genset can be calculated as follows.
  • P = 975 kW
  • Efficiency = 92% = 0.92
  • H = 975 x ((1/92%) – 1)
  • H= 84.78 kW
  • H = 975 x ((1/92%) – 1) x 56.9
  • H = 4824 Btu/min

 Types of Ventilation System:

  • Type:1 (Preferred Design) (Routing Factor of 1)
  • Outside air is brought into the engine room through a system of ducts. These ducts should be routed between engines, at floor level, and discharge air near the bottom of the engine and generator. .
  • Ventilation air exhaust fans should be mounted or ducted at the highest point in the engine room. They should be directly over heat sources. This system provides the best ventilation with the least amount of air required.
  • Type 2 (Skid Design) (Routing Factor of 1)
  • Outside air into the engine room through a system of ducts and routes it between engines.
  • Type 2, however, directs airflow under the engine and generator so the air is discharged upward at the engines
  • The most economical method to achieve this design is to use a service platform. The platform is built up around the engines and serves as the top of the duct
  • Ventilation air exhaust fans should be mounted or ducted at the highest point in the engine room. They should be directly over heat sources.
  • This system provides the best ventilation with the least amount of air required.
  • Type 3 (Alternate Design) (Routing Factor of 1.5)
  • If Ventilation Type 1or Type 2 is not feasible, an alternative is Type 3; however, this routing configuration will require approximately 50% more airflow than Type 1.
  • Outside air is brought into the engine room utilizing fans or large intake ducts. The inlet is placed as far away as practical from heat sources and discharged into the engine room as low as possible. The air them flows across the engine room
  • Ventilation air exhaust fans should be mounted or ducted at the highest point in the engine room. Preferably, they should be directly over heat sources
  • Type 4 (Less Effective Design) (Routing Factor of 2.5)
  • If Ventilation Type 1, Type 2 and Type 3 are not feasible, then Type-4 method can be used; however, it provides the least efficient ventilation and requires approximately two and a half times the airflow of Ventilation Type 1
  • Outside air is brought into the engine room using supply fans, and discharged toward the turbocharger air inlets on the engines.
  • Ventilation exhaust fans should be mounted or duct from the corners of the engine room
  • This system mixes the hottest air in the engine room with the incoming cool air, raising the temperature of all air in the engine room.
  • It also interferes with the natural convection flow of hot air rising to exhaust fans.
  • Engine rooms can be ventilated this way, but it requires extra large capacity ventilating fans.

Ventilation for Generator:

  •  When Generator set installations in Room proper ventilation is required for Generator set.
  • A properly designed engine room ventilation system will maintain engine room air temperatures within 8.5 to 12.5°C (15 to 22.5°F) above the ambient air temperature.
  • For example, If the engine room temperature is 24°C (75°F) without the engine running, the ventilation system should maintain the room temperature between 32.5°C (90°F) and 36.5°C (97.5°F) while the engine is in operation.
  • Ensures engine room temperature does not exceed 49°C (120°F).
  • Required Ventilating Air is calculated as
  • V=((H / D x Cp x T)+ Combustion Air) X F
  • Where:
  • V = Ventilating Air (m3/min), (cfm)
  • H = Heat Radiation i.e. engine, generator, aux (kW),(Btu/min)
  • D = Density of Air at air temperature 38°C (100°F). The density is 1.099 kg/m3 (0.071 lb/ft3)
  • CP = Specific Heat of Air (0.017 kW x min/kg x °C),(0.24 Btu/LBS/°F)
  • T = Permissible temperature rise in engine room (°C), (°F)
  • F = Routing factor based on the ventilation type
  • Example: The engine room for generator set has a Type 1 ventilation routing configuration and a dedicated duct for combustion air. It has a heat rejection value of 659 kW (37,478 Btu/min) and a permissible rise in engine room temperature of 11°C (20°F).
  • V=((659 / 1.0099X0.017X11)+ 0)X1
  • V = 3206.61 m3/min
  • V=((659 / 0.071 X 0.024 X 20)+ 0)X1
  • V = 109970.7 cfm

Thumb Rule-12 (Quick Reference of DG Set)


 

Standard Size of The DG sets

KVA KVA KVA KVA KVA
7.5 KVA 20KVA 35 KVA 62.5 KVA 100 KVA
10 KVA 25 KVA 40 KVA 75 KVA 125 KVA
15 KVA 30 KVA 50 KVA 82.5 KVA 200 KVA

 

D.G Foundation Bar Size

Rating of D.G set Size of Bar
Up to 82.5 KVA 10MM
100 KVA To 200 KVA 12MM
250 KVA to 500KVA 16MM

 

Minimum Capacity of  Fuel Service Tank

AS per CPWD
Capacity of DG set Minimum Fuel Tank Capacity
Upto 25 KVA 100 Liters
Above 25 to 62.5 KVA 120 Liters
Above 62.5 KVA to 125 KVA 225 Liters
Above 125 KVA to 200 KVA 285 Liters
Above 200 KVA to 380 KVA 500 Liters
Above 380 KVA to 500 KVA 700 Liters
Above 500 KVA to 750 KVA 900 Liters

 

Battery Size for D.G Set

                                                           AS per CPWD

DG Set Capacity Battery Capacity (AH) Cu Cable Size (Sq. mm) Electrical System (Volts)

Up to 25 KVA

88 35

12

Above 25 KVA upto 62.5 KVA

120 50

12

Above 62.5 KVA up to 82.5 KVA

150 50

12

Above 82.5.KVA up to 125 KVA

180 50

12

Above 125 KVA up to 500 KVA

180 70

12

Above 500 KVA

360 70

24

 

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/sq meter)
750-2000 600 mm
625 400 mm
320-500 400 mm
200-320 400 mm
82.5 -200 400 mm
Upto 82.5 200 mm

 

Foundation & Earthing for D.G Set

As Per CPWD

Ieam Descriptions
D.G set inside Room A PCC foundation (1:2:4, M-20 grade) of approximate depth 150 mm above the finished Generator set 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 Room A PCC (1:2:4, M-20 grade) foundation  of  weight  2.5  times  the  operating  weight  of  the  Generator set  with  enclosure  or  as recommended by the Generator set 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.
Earthing Copper 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 Sets 2No’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 Detail according to Size

D.G Size (KVA) L x W x H (Canopy) mm Approx Weight (Kg) Fuel Tank (Ltrs) Fuel Consumption (Ltr/hr) Oil Consumption (Ltr/hr)
12.5 2040 x 1230 x 1450 1050 60 2.3 0.02
15 2040 x 1230 x 1450 1050 65 2.3 0.02
20 2240 x 1230 x 1450 1300 65 3.7 0.03
30 2510 x 1130 x 1450 1300 65 6.3 0.03
40 3350 x 1180 x 1650 1500 100 7.8 0.03
50 3350 x 1180 x 1650 1500 100 8.3 0.03
62.5 3350 x 1180 x 1650 1930 150 10.5 0.03
75 3605 x 1405 x 1600 1950 150 13 0.03
100 3940 x 1700 x 1850 2500 300 15.7 0.05
125 3950 x 1700 x 1850 2700 300 19 0.05
140 4600 x 1850 x 1950 3580 300 22.6 0.06
160 4600 x 1850 x 1950 3720 450 25.9 0.14
180 4970 x 1730 x 2045 3870 450 27.7 0.14
200 4970 x 1730 x 2045 3950 450 29.8 0.14
250 4970 x 1730 x 2050 4660 450 37.7 0.15
275 5700 x 2030 x 2515 5860 450 50 0.15
320 5700 x 2030 x 2515 5860 450 57 0.3
400 5905 x 2030 x 2520 6180 990 65.1 0.3
500 6205 x 2030 x 2550 6990 990 81.3 0.3

 

FUEL CONSUMPTION  FOR DG SET:

Generator KVA Diesel consumption Liter per hour
5 1.25
15 2.91
20 4.78
25 4.78
30 6.55
40 8.11
50 10.19
62.5 10.92
75 13.52
82.5 13.52
125 19.76
140 23.4
200 30.99

 

D.G Spacing Guidance

Description DG set with Acoustic Enclosure Open DG set in room.
in Open Area in Closed Area
Free space on both sides Min. 1.5 m Min. 1.5 m Min. 2 m
Free space at front side (Radiator Hot air outlet at Front) Min. 3 m Min. 3 m N/A
Free space at front side (Radiator Hot air outlet at Top) Min. 1.0 m Min. 1.5 m N/A
Free space at rear side
(Alternator)
Min. 2 m Min. 2 m Min. 2 m
Fresh air inlet opening area N/A N/A Min 1.5 times of the Radiator area.
Hot air discharge opening area N/A N/A Min 2.5 times of the Radiator area.
Distance between two sets Min 1.5 meter between two
canopies
Min 1.5 meter between
two canopies
Min 1.5 meter between two foundations.

 

Simple Calculation of Flood Light, Facade Light, Street Light & Signage Light-(Part2)


(B) Facade Lighting:

  • Normally Facade Lighting are used to illuminate Building area from Outer Side. 
  • There are three factor should be consider while designing of outdoor Facade Lighting.
  1. Setback
  2. Spacing
  3. Aiming

1) Setback:

  • The recommended setback should be 3/4 times the building height. 
  • If a building is 10 Meter tall, the recommended setback is 7.5 Meter from the building. 
  • If the locating the floodlight closer to the building will sacrifice uniformity and If setting it further back will result in loss of efficiency.
  • Setback distance = 3/4 x Building height
  • Setback distance =3/4 x (10 Meter) = 7.5 Meter 

a

2) Spacing:

  • Spacing of floodlights should not be exceeding two times the setback distance. 
  • If the setback is 7.5 Meter the floodlights should not be placed more than 15 Meter apart.
  • Spacing = 2 x setback distance
  • Spacing=2 x 5  = 15 Meter

b

3) Aiming:

  • The floodlight should be aimed at least 2/3 the height of the building.
  • If a building is 10 Meter high, the recommended aiming point is approximately 6.6 Meter high. 
  • After installation aiming can be adjusted to produce the best fine appearance. 
  • Aiming Point = 2/3 x Building Height.
  • Aiming Point =2/3 (10 Meter) = 6.6 Meter high

c

(C) Sinage Lighting:

  • Normally Sinage Lighting are used to illuminate Sinage Board either Floor Mounted or Pole Mounted
  • There are three factor should be consider while designing of Sinage Board Lighting.
  1. Setback
  2. Spacing
  3. Aiming

1) Setback:

  • When using floodlights to light a sinage, the setback should be 3/4 the sign height
  • If the sinage height is 18 Meter then the setback distance would be 13.5 Meter. 
  • If the floodlight closer to sinage will sacrifice uniformity while setting it further back will in a loss of efficiency.
  • Setback distance = 3/4 x sinage height
  • Setback distance =3/4 (18 Meter) = 13.5 Meter.

d

2) Spacing:

  • The spacing floodlights should not be exceed two times the setback distance. 
  • If the setback is 13.5 Meter, the floodlights should not be placed more than 27 Meter apart. 
  • Spacing = 2 x setback distance.
  • Spacing = 2 x 5 (Meter) = 27 Meter.

e

3) Aiming:

  • The floodlight should be aimed at least 2/3 up the sign.
  • If a sign is 18 Meter tall, then the floodlight should be aimed approximately 12 Meter high. 
  • Aiming can be adjusted to produce the best appearance. 
  • Mounting a full or upper visor to the floodlight can reduce unwanted glare. 
  • Aiming point = 2/3 x sign height
  • Aiming point =2/3 (18 Meter) = 12 Meter high

f

Street Light Pole Height & Spacing (as per CPWD):

  • There are four type of Street Light Pole arrangement.
  • One side Type.
  • Staggered Type.
  • Opposite Type.
  • Central Type.
  • As per CPWD we can calculate Pole Height and Spacing as per under

(1) One side Street Light Pole arrangement.

  • Pole Height = Width of Road.
  • Pole Spacing = 3 to 4 Times Height of Pole.
  • If the Road width is 8 Meter than
  • Pole Height=8 Meter
  • Pole Spacing =24 to 32 Meter.

g

(2) Staggered Type Street Light Pole arrangement.

  • Pole Height = 0.8 time Width of Road.
  • Pole Spacing = 3 to 4 Times Height of Pole.
  • If the Road width is 8 Meter than
  • Pole Height=6.4 Meter
  • Pole Spacing =24 to 32 Meter.

h

(3) Opposite side Street Light Pole arrangement.

  • Pole Height = 0.5 time Width of Road.
  • Pole Spacing = 3 to 4 Times Height of Pole.
  • If the Road width is 8 Meter than
  • Pole Height=6.4 Meter
  • Pole Spacing =24 to 32 Meter.

(4) Central Street Light Pole arrangement.

  • Pole Height = 0.8 time Width of Road.
  • Pole Spacing = 3 to 4 Times Height of Pole.
  • If the Road width is 8 Meter than
  • Pole Height=4 Meter
  • Pole Spacing =24 to 32 Meter.
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