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

• 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 

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

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) 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.

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.

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

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.

(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.

(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.