IEC-French Standard Typical Residential from NFC 15-100 Requirements

IEC French Standard Typical Wiring diagram and electrical installations required by NFC 15-100

SUPPLY
Usually single phase (230 V / 50 Hz). Earth is usually local (TT system). The protective conductor is mandatory in every circuit. An AD fuse is installed on the phase in conjunction with the main circuit breaker.

METER
A single kW/h meter is supplied. If an optional off-peak power fare is subscribed, a 2-fares meter with pilot-line switching is installed.

MAIN CIRCUIT-BREAKER
This device has 3 functions:
- Acts as the main switch of the installation
- Limits the current consumption to a pre-settled level of the contract with electricity supplier
- Provides protection against indirect contact through a residual current protection (type S, 500 mA).

LIGHTNING PROTECTION
The installations supplied by an overhead electric Iine and located in high risk lightning areas have to be protected by a Surge Protective Device (SPD) installed downstream of the main residual current circuit breaker. The Surge Protective Device has to be connected to the main earth terminal of the consumer unit.

CONSUMERS DISTRIBUTION BOARD
All the protection and control functions of the electrical installation are located in the main household trunking (called GTL). The power distribution panel board and the communication panel
board are located in the GTL.

POWER DISTRIBUTION PANEL BOARD
This panel board concentrates all the control and protection functions of the electrical installation. The protection against overcurrent (short circuit and overload) is provided by circuit-breakers or fuses. All the circuits have to be protected by a 30 mA RCD in order to provide the complementary protection against the direct contacts. Other devices could be located in the panel board as:
- Time switches and time delay relays
- Bell transformer
- Power relays (heating, etc)
- Latching relays for lighting
- Signalling lamps
- Daylight/dusk switches
- Dimmers
- Land-shedding relays
- Off-peak power relays
- Buzzer or bell.

CIRCUIT PROTECTION AGAINST OVERCURRENT
Each circuit has to be protected against overcurrent at its origin. The overcurrent protection device shall ensure the simultaneous breaking of both phase and neutral conductors. The protection device should be a miniature circuit breakers or a fuse cartridge.

SPECIALIZED CIRCUITS
Some appliances (e.g. washing machine, freezer, dishwasher, etc) should be supplied by a dedicated circuit having the appropriate cross sectional area and overcurrent and RCD protection. They will be connected either via a socket or via a cable outlet box (e.g. oven, cooking plate, water-heater).

SOCKET OUTLETS
The socket outlet circuits are installed in a star configuration. The maximum number of socketoutlets is 8 on a 2.5 mm2 circuit and 5 on a 1.5 mm2 circuit. Socket outlets are of the earthed type 2P+E. Shutters are mandatory for all type of socket-outlets up to 32 A.
PLUGS
They can be 2P or 2P+E type. The flat bodied 2P type should have sleeved pins. Specific 20 A and 32 A plugs are also available for high power circuits.

LIGHTING POINTS
The lighting circuits are installed in a star configuration. A maximum of 8 points per circuit is allowed, each controlled by switches or dimmers. Multiple-point control of lighting is usually achieved by latching relays and push-buttons. The use of time-lag switches for the light control in public areas is also recommended.

EARTHING
The earthing terminal is usually provided by a closed loop foundation earth electrode. Supplementary bonding of metal fittings in bathroom, kitchens, etc., is mandatory.

CABLING
Most domestic wiring is run either in plastic surface mounted trunking or in plastic flushed-in conduit systems. Generally PVC insulated solid copper conductors are used in fixed wiring. Concerning the surface-mounted trunking systems, the protection against the external influences has to be ensured throughout the entire length of the circuit.

ELECTRICAL ACCESSORY INSTALLATION
Switches, sockets, etc., should be installed in a flush or surface mounted box or in an especially designed trunking system. All the accessories have to be screw fitted.

OUTDOOR CIRCUITS
The use of a 30 mA RCD protection is mandatory for the protection of the domestic outdoor circuits. Outdoor sockets should be at least IP 44.

BATHROOMS
Specific rules apply for circuits in bathrooms.

COMMUNICATION BOARD
In the domestic installation a communication board is installed in the main household trunking (GTL). It is the central part of the communication network of the dwelling. Each room of the dwelling is supplied by a twisted pair cable originating from the communication board and terminating with an RJ 45 socket. This communication network is able to provide different services such as telephone, Ethernet and TV.

British Standard BS7671

BS 7671

BS7671 free pdf link : http://bit.ly/1QNIdGf

British Standard BS 7671"Requirements for Electrical Installations. IET Wiring Regulations.", informally called The "Regs" (wiring regulations), is the national standard in the United Kingdom for electrical installation and the safety of electrical wiring in domestic, commercial, industrial, and other buildings. In general, BS 7671 applies to circuits supplied at nominal voltages up to and including 1000 volts AC or 1500 volts DC. The standard therefore covers the 230 volt 50 Hz AC mains supply used in the UK for houses, offices, and commerce.

The current version is BS 7671:2008+A3:2015 (the 17th edition incorporating Amendment 3:2015) issued in 2008 and updated ("Amendment no. 3") in January 2015 and mandatory from July 2015, although some provisions only come into force in January 2016.BS 7671 is also used as a national standard by other countries, which base their wiring regulations on BS 7671.

The first edition was published in 1882 as the "Rules and Regulations for the Prevention of Fire Risks arising from Electric Lighting." The title became "General Rules recommended for Wiring for the Supply of Electrical Energy" with the third edition in 1897, "Wiring Rules" with the fifth edition of 1907, and settled at "Regulations for the Electrical Equipment of Buildings" with the eighth edition in 1924. It did not become a recognized British Standard until the publication of the 16th edition in 1992.

The standard is maintained by the Joint IET/BSI Technical Committee JPEL/64, the UK National Committee for Wiring Regulations, and published by the IET (formerly IEE). Although the IET and BSI are non-governmental organisations and the Wiring Regulations are non-statutory, they are referenced in several UK statutory instruments, and in most cases, for practical purposes, have legal force as the appropriate method of electric wiring. The BSI (British Standards Institute) publish numerous titles concerning acceptable standards of design/safety/quality across different fields.

Since the 15th edition (1981), these regulations have closely followed the corresponding international standard IEC 60364. In 1992, the IEE Wiring Regulations became British Standard BS 7671 and they are now treated similar to other British Standards. BS 7671 has converged towards (and is largely based on) the European Committee for Electrotechnical Standardization (CENELEC) harmonisation documents, and therefore is technically very similar to the current wiring regulations of other European countries.

IEC – German Standard Typical residential wiring diagram issued from VDE 0100 requirements for electrical installations

IEC – German Standard
Typical residential wiring diagram issued from VDE 0100 requirements for electrical installations.

SUPPLY
May be single phase (230 V-50 Hz) or - in the majority of cases - 3 phases (400 / 230 V-50 Hz). Max. Tolerance (voltage): + 6% / -10%. TN- and TT- systems are in use. TT- systems are the most common in domestic installations. There is usually one meter. Facilities are provided with a second meter for special tariffs, etc. A fuse isolator unit allows all phases to be cut-off, isolating the whole domestic installation.

DISTRIBUTION BOARD
The distribution board usually contains pre-fuses (for example 3 x 32 A), RCBO 30 mA for household applications (1 or 3 poles). Transformer(s) as for entry door systems, MCB (16 A for general circuits up to 32 A (3 poles) for (water) heating systems). Time lag switches in dwellings. These devices are all mounted on a DIN-Rail.

POWER CIRCUITS
Single phase up to 3 WA, 7.3 KVA: 3 phases. Electrical appliances having a high power consumption (cookers, washing machines, etc.) are supplied via a specific circuit and connected either to 16 A socket-outlet or cable outlet or to a specific socket Perilexi or CEE 17. It is not uncommon to find 3 phases appliances. Protection rating and cable size of each circuit are calculated according to the appliance (min section 1.5 mm2 Cu 16 A).

GENERAL CIRCUITS
These circuits supply both lighting points and socket outlets. The rating of the protective device is usually 16 A. There is no limitation of the number of outlets on a circuit. This limit is calculated according to expected/probable use of the circuit. Socket outlets are generally of the 2P+E type “German". These plugs are non-polarized. All German socket outlets are earthed. In general, the protective conductor is distributed throughout all circuits. For class II devices < 2.5 A, the Euro-plug is used. The wire cross-section of the fixed installed cables is normally 1.5mm² (protected by a 16 A Circuit Breaker).

DAMP & OUTDOOR
INSTALLATIONS
Special rules apply, in particular for IP rating of accessories and equipment and RCD Protection.

EARTHING
Earthing is local, usually through a foundation earthing arrangement. All metallic services shall be bonded (gas and water pipe, heating, waste systems, etc.) with a 10 mm2. In bathrooms the local equipotential bonding could have a cross sectional area of 4 mm2. Neutral is re-earthed in the control panel. A protective conductor is distributed to all socket outlets.

INSTALLATION RULES
The installation must comply with the requirements of VDE 0100 and the “TAB” (TAB = technische Anschlussbedingungen = special requirements of the energy supplier, for example EON, RWE, EnBw or Wattenfall). Installations may only be erected by registered and qualified electricians.

BATHROOMS
Special rules apply to bathrooms. The room is divided into different zones:

Zone “Bereich 0”: Electrical equipment are not allowed. Only special SELV-devices, max.12V AC or max. 30V DC are allowed. The power supply for these SELV-circuits is not allowed in “Bereich 0” and in “Bereich 1”.

Zone “Bereich 1”: Only fixed installed electrical equipment for hot water production and SELV or PELV –devices (max. 25V AC or max. 60V DC) are allowed. The power supply for the SELV- or PELV -circuits has to be installed outside “Bereich 0” and in “Bereich 1”.

Zone “Bereich 2”: Only Electrical equipment supplied by SELV- or PELV (max. 25V AC or max.60V DC) are allowed. Only shaver sockets according to DIN EN 61558-2-5 are allowed. In bathrooms, an additional equipotential bonding and RCDs (30 mA) protection for socket outlets are mandatory (Details in the DIN VDE 0100-701).

HOME AND BUILDING CONTROL
KNX (EIB) ISO/IEC14543, EN50090 is common in big and luxury installations.

ACCESSORIES
They shall comply with the appropriate VDE standards. Flush accessories are fitted in boxes. Claw-mounting and screw-mounting are used.

ENERGY SAVING & REGENERATIVE POWER GENERATION
Single-room heating control and time-controlled hot water supply is mandatory due to the EnEV (energy saving directive). Airproof installations are common in low energy buildings. More and more roofs are equipped with photovoltaic cells

NEC-Standard Typical Residential Wiring Diagram and Electrical Installation Requirements from NEC

NEC-Standard
Typical Residential Wiring Diagram and Electrical Installation Requirements from NEC

SUPPLY
Domestic supply is usually 2 phases (120 V/240 V - 60 Hz). 2 phases + neutral are supplied. Neutral is re-earthed at entry. Earth is local.

METER
Usually a weatherproof unit outside the house.

SERVICE PANEL
Ratings of 60 A, 100 A, 150 A and 200 A exist. The Service Panel (or Service Entrance Panel) usually contains a Main Disconnect device and the necessary protective devices for the sub-circuits.

POWER CIRCUITS
Appliances having heavy power consumption (ranges, water-heaters, etc.) are supplied on a specific circuit, often 120/240 V. Various socket outlets of appropriate ratings are available, these are noninterchangeable, thus 2 Phase + Neutral + Earth plug cannot be fitted to a 2 Phase + Earth socket, etc.

GENERAL PURPOSE CIRCUITS
These are 120 V-15 A and supply socket outlets (IP+N+G).These circuits supply bedrooms, etc. where the use of a large number of appliances is unlikely. Note that all general purpose socket outlets must be of the grounding type.

APPLIANCE CIRCUITS
The 120 V-20 A circuits supply areas such as kitchens,dining-rooms. etc., when there is a likelihood of more intensive use of appliances. The NEC [National Electrical Code) requires at least two appliance circuits for a domestic installation.Only socket outlets may be supplied on an appliance circuit. All domestic use NEMA 5-15R and 5-20R receptacles must be tamper resistant.

PLUGS
Various types of plugs exist to match the various configurations of socket outlets.

OUTDOORS
Outdoor socket outlets must have 6 mA GFCI protection and be housed in a weatherproof enclosure.

GROUND-FAULT CIRCUITINTERRUPTERS
(GFCI)
All domestic use 125 V - 15 A and 20 A socket outlets in the following locations must be protected by GFCI having a trip level sensitivity of 6 mA:
- Bathrooms
- Garages
- Kitchens
- Basements
- Outdoors
- Laundry and utility sinks (when socket outlets are within 6 feet).

ARC-FAULT CIRCUITINTERRUPTERS
(AFCI)
All domestic use 120 V - 15 A and 20 A branch circuits supplying outlets in living rooms, dining rooms, family rooms, bedrooms and similar areas must be AFCI protected.

TAMPER RESISTANT
(SHUTTERED) SOCKET OUTLETS
All domestic use 125 V - 15 A and 20 A socket outlets must be Tamper Resistant (shuttered).

EARTHING (GROUNDING)
The use of ungrounded (2P) sockets in domestic installations is no longer allowed by the NEC. Earth can be distributed in the installation in one or two ways:
- By a specific earth conductor distributed along with live + neutral
- By using metallic boxes, conduit and sheathed cables and using this metallic system as earth.
All conductive non-current carrying parts of the electrical system should be effectively bonded to earth.

Polarity:
Polarity is conserved throughout the installation.

Live (hot):
Terminal screws brass colour; conductors insulated in black

Neutral:
Terminal screws silver or marked white or W; conductor insulated in white.

Ground:
Terminals green colour or marked G; conductors insulated in green or wire is left bare.

Cabling:
Various types of cables are used in domestic installations, the most frequent are:

NM. Non-metallic sheathed; AC, Metal-clad cable.

Similarly various types of conduits are also encountered:
- Rigid steel conduit
- Intermediate metal conduit
- Thinwall metal conduit
- Flexible metal conduit
- Rigid non-metallic conduit
- Surface raceway.

ELECTRICAL ACCESSORY
INSTALLATION
Accessories are fitted in standard boxes, either metal or plastic, the most common sizes being 2 inches by 4 inches and 4 inches by 4 inches.

IEC British Standard Electrical Wiring Installations

IEC – British Standard

Typical residential wiring diagram issued from BS 7671 requirements for electrical installations.

INSTALLATION GUIDELINES

BS 7671, “Requirements for Electrical Installations” is published by the Institution of Engineering and Technology and BSI, it governs all domestic electrical installations (and many other types).

SUPPLY

Since 1 January 1995 nominal voltage in UK is 230 V +10% / - 6% AC at 50 Hz. Earth is normally supplied but may be local.

HOUSE SERVICE CUT-OUT

The Electricity Boards protective device, usually a 80 A or a 100 A HRC Fuse. It is sealed in a special housing to prevent tampering.

METER

Usually a dual meter for normal and off-peak energy consumption, sealed to prevent tampering.

CONSUMER UNIT

It houses the main switch which isolates the total installation and the individual circuit protection devices. The consumer unit should comply with BS EN 60439-3. Circuit protection is normally provided by miniature circuit breakers to BS EN 60898 (older installation may have fuse protection). The consumer unit may also contain one or more residual current devices providing additional protection in all or part of the installation (older installations may not have RCD protection provided).

POWER CIRCUITS

Appliances having heavy current consumption (cookers, waterheaters, etc.) should each be supplied on a specific circuit of the appropriate rating. In general, a double pole switch controls and isolates the appliance when necessary and the connection of the appliance can be made either directly to the switch or via a flexible cable outlet. Switches should conform to BS EN 60669 and Cooker Control unit to BS 4177.

SOCKET OUTLET CIRCUITS

Socket outlets should comply with BS 1363-2 and are usually of the switched type. They are usually supplied via a ring final circuit which is a circuit running from the protection device to each outlet and then returning to the protection device. Permanent connections to a ring final circuit and branches off the ring are made via fused connection units to BS 1363-4. Socket outlets to BS 546 are no longer used in domestic installations in the UK but are still widely used in some other countries.

PLUGS

Plugs of domestic appliances should conform to BS 1363-1. They contain a fuse link to BS 1362 of a rating appropriate to the flexible cord of the appliance (max =13 A). Domestic appliances sold in UK must be fitted with a BS 1363-1 plug, further the UK plug and socket safety regulations require mandatory third party certification of plugs.

LIGHTING CIRCUITS

Usually a circuit supplies several lighting points in turn. A lighting point usually consists of a ceiling rose in which incoming, outgoing and switch connections are made and a pendant flexible cord supplying an attached lamp holder or may be a complete luminaire. Light switches should meet BS EN 60669-1. Dimmers should meet BS EN 60669-2-1.

BATHROOMS

The wiring regulations are very strict. Every switch or other means of electrical control or adjustment shall be so situated as to be normally inaccessible in the bathroom. The required Ingress protection is managed through a series of defined zones progressively from the bath or shower. Pull cord switches are allowed, shaver sockets with isolating transformers are also allowed but should conform to BS EN 61558-2-5.

OUTDOORS

Any socket outlet provided outdoors or intended to supply outdoor equipment (e.g. electric lawn-mowers should have a 30 mA RCD protection).

EARTHING

Socket outlets to BS1363-2 have provision for earthing. A protective conductor (which could also be steel conduit) is generally required for all low voltage circuits (1000 V a.c. between conductors) and its continuity must be proved. All main incoming services, for example, water and gas pipes and metallic parts of the building structure, etc. must be bonded and connected to the main earthing terminal of the installation. In addition it may be necessary to supplementary bond water and waste pipes, sinks and other metallic items such as central heating radiators. However in rooms with a fixed bath or shower, supplementary bonding must be applied to simultaneously accessible metal parts unless RCD protection of all circuits in the bathroom is provided.

POLARITY

The polarity is conserved and marked throughout the installation:

Live:

Terminals marked L are for brown coloured insulated conductors, both solid conductors and flexible conductors are coloured brown

Neutral:

Terminals marked N are for blue coloured insulated conductors, both solid conductors and flexible conductors are coloured blue.

Earth:

Terminals marked E or are for green/yellow coloured insulated earth conductors, both solid conductors and flexible conductors are either coloured green or yellow or sleeved as such.

CABLING

Most domestic wiring is done in flat p.v.c. insulated and sheathed 3 core cable (flat twin and earth). Maximum use is made of floor and internal wall voids to run cables. Surface installations are run in conduit or trunking, these can be plastic or metal. Various British standards govern the design and construction of conduits, trunking and cable. Wiring accessories may be installed in plastic or (more often) metal flush boxes to BS 4662. Surface installations are made in appropriate proprietary boxes.

Cost Estimation as per Philippine Electrical Code

All electrical system design, installation and cost estimation for single and multi-family dwelling units are under the provisions of the Philippine Electrical Code (PEC) and other relevant laws and stndards.

COST ESTIMATION GUIDE

1. Prepare paper, pencils, scale and rulers. Mark papers indicating the panel no., circuit number and the location of the circuit run.

2. Study plans, drawing and specifications.

2.1 Coordinate with Civil, Mechanical and Architectural Estimators about the following

2.1.1 Height between floors

2.1.2 Drop ceilings and ceiling supports

2.1.3 Height between finish floor and ceilings

2.1.4 Major beams and columns thru which conduits may not pass

2.1.5 Other architectural/civil/mechanical drawings indicating positions of the lights, special outlets or aircon unit equipment.

2.2 Check and make a physical count of the following

2.2.1 Lighting fixtures – number of each type of fixtures

2.2.2 Convenience outlets – duplex

2.2.3 Special outlet

2.2.4 Panel boards – make a complete description of each panel board.

The description should include:

a. main breaker rating or lugs only

b. no. of branches per ampere trip

c. kAIC

2.2.5 Other electrical equipment to be supplied by contractor

2.3 Study carefully the circuit runs and the riser diagram together with theschedule of load.

3. Determine the approximate length of wire and conduit per circuit.

3.1 For the conduit (each circuit) - measure the length from the last outlet to the panel using the scale. The trace of the route must be followed as per drawing.

3.2 For the wire – measure the length between outlets and the length shall be multiplied by the no. of wires. The sum of the products (lengths x the no of wires) shall be the approximate length of wire.

3.3 Sum up the total length of conduit per size and divide by 3. Round off and add 10%.

3.4 Sum up the total length of wire for each size and divide by 150 to get the no of rolls. Round off and add 10%.

3.5 Set aside the papers and data temporarily.

4. Determine the approximate length of wire and conduct for the panel homerun to the main panel or main distribution panel.

4.1 Conduits – measure the length of the run. Check the shortest possible route and avoid obstructions. Total length divide 3 and add 5%

4.2 Wire – multiply the length of conduct by the following constants

a. 2- for two-wire single phase

b. 3- for two-wire single phase with neutral

c. 3- for three-wire, 3-phase

d. 4- for 3-phase, 4 wire

5. Boxes

5.1 Octagonal boxes – provide one box for each lighting fixtures

5.2 Utility box 4”x 2” – provide one box for each switch, duplex outlet or special outlet (small)

5.3 Square box 4” – provide one box if the conduits terminating exceed 4 conduits or special big outlets.

5.4 Square box 4 11/16 – provide one box for one-inch diameter conduits or for special purpose outlets. Also provide one box for multiple (6 or more) terminations.

5.5 Pull boxes – provide one box for every 18 meters of conduits length depending upon the length of run. Other pull boxes may be designated by plans. Check with the designer/consultant about the sizes.

6. Fittings

6.1 For PVC pipes

6.1.1 Couplings – provide 1 coupling for every length plus 1 coupling for every termination.

6.1.2 Elbows – provide 1-90⁰elbow for every quarter turn for sizes of 32 mm (1 1/4”) and above.

6.1.3 Cement – provide 1 can forevery 10 length of conduit.

6.1.4 End bells – provide 1 for every termination.

6.2 For RSC conduits

6.2.1 Coupling – provide 1 additional coupling for every 5 lengths

6.2.2 Elbows- provide one 90-degree elbow every 90-degree turn for sizes of 25 mm (1”) diameter above.

6.2.3 Locknut and bushing – provide one pair for every termination.

6.3 For electrical metallic tubing

6.3.1 Couplings- one set for every length

6.3.2 Elbows- use on site bended EMT

6.3.3 Adapters w/ locknut and bushing- for every termination are 1 adapter and 1 pair of locknut and bushings.

6.4 Straps – two (2) straps for every length of conduit. In sizes of 25 mm diameter and above use clamps especially for RSC or EMT conduits.

6.5 Other fittings

6.5.1 Wire trays/cable trays – check with drawings and consultant/designer

6.5.2 Cable trough / duets – check w/ drawings especially that the drawings may have specific sizes.

7. Other Considerations

7.1 for lighting fixtures – add 1 m of wire for every termination or lighting fixtures

7.2 for convenience outlets

a. Add 0.8 m. for every C.0. to the length of pipe and 1m of wire for every termination

b. Add 0.4 m above the height of counters if the C.O. is above the counter in addition to the height of the counter. Add also 1 m of wire for every termination.

7.3 for homeruns terminating a panel boards add 2 meters of wires for every circuit.

7.4 provide an empty conduit for every spare circuit per panel

7.5 normally the electronic and communication circuits will be in separate sheets and have an ECE estimate

7.6 provide 1 connector for every termination # 6 up.

8. Summarize the lists of materials as follows

8.1 conduits – total of each size

8.2 fittings - total of each type/size

8.3 boxes - total of each type/size

8.4 panels – per panel and lowest canvassed price

8.5 Wires - total length of each wire size

8.6 Connectors – (solderless less) total termination of each size for wire #6 wire and above.

8.7 Tape – 1 roll PVC tape for every 100 m of wire plus 1 roll of rubber tape for every 200m of wire.

8.8 other materials must be itemized.

9. Costing

9.1 get the unit cost for each item and deduct all discounts.

9.2 from the total cost add 5% to 10% mark up

9.3 For all others materials like duets, panels, transfer switches, safety switches, and etc.- get the price from the fabricator net (less discounts) and add 5% markup.

10. Preparation of Bid or Asking Price

10.1 Material cost

Conduits Fitting Boxes__________________________

Wires and wiring Devices________________________

Lighting fixtures _______________________________

Safety Devices_________________________________

Service Entrance and Mains_______________________

Others________________________________________

_______________________

Subtotal A

10.2 Labor Cost

10.1 If materials are imported

a. Labor Cost is 20 % of subtotal A

b. Supervision is 3% of subtotal A

c. Mark-up is 1.25 % of subtotal A

10.2 If the conduits and most materials are locally available

a. Labor cost is 25 % to 30% of subtotal A

b. Supervision cost is 4% to 5% of subtotal A

c. Mark up cost is 2 % of subtotal A

10.3 Contingencies – an allowance of 5% to 7% of the total cost of materials and labor

10.4 Overhead – this include the cost of transportation, office staff tools and equipment depreciation, papers and office supplies to representation, and cost of money.

- Normally 7% to 10% of the cost of materials is the cost of overhead.

10.5 Permits – show the plans to the municipal electrical engineer or his assistant and request for an estimate. Add 5% to cover the exingencies.

10.6 a. the sum cost as computed in 10.1 and 10.5 is to be multiplied by 0.03 to get the contractor’s tax.

b. Add the contractor’s tax to the sum of sections 10.1 to 10.5 and round off. This will be your bid price.