1. Systems Of Wiring Buildings
There are three general systems of arranging the conductors within a building for electric lightingpurposes.
Tree or Single Main System,
Subdivided Main System,
Three-Wire System.

2. The Tree Or Single Main System

3. Subdivided Main System

4. The three-wire system

5. DISTRIBUTION BOARDS

6. Electrical System Must meet several conditions to be satisfactory:
Be safe
Be convenient
Be expandable
Look neat
Provide sufficient current

7. Service Entrance
Electrical power comes by overhead or underground wires
Power company provides:
Transformer
Service drop
Appropriate wiring to entrance head

8. Service Entrance
Transformer: converts high voltage from power lines to 240 volts for home and farm installations
Service drop: assembly of electrical wires, connectors, and fasteners used to transmit electricity from transformer to entrance head to service entrance panel

9. Service Entrance
Entrance head: waterproof device used to attach exterior wires to interior wires of a building
Modern systems – most have entrance cables buried underground
No need for entrance head
Service entrance panel: box with fuses or circuit breakers where electricity enters a building

10. Branch Circuits Most circuits begin from service entrance panel
Called branch circuits because they branch out into a variety of places and for a variety of purposes
Generally includes only one motor or a series of outlets or a series of lighting fixtures
Important to provide correct size of wire and fuse or circuit breaker for load on each circuit

11. Branch Circuits
Fuse: plug or cartridge containing a strip of metal that melts when more than a specified amount of current passes through it
Must be replaced if it blows
Circuit breaker: a switch that trips and breaks the circuit when more than a specified amount of current passes through it
Can be reset after being tripped

12. Branch Circuits
Fuses and circuit breakers designed to protect circuits from damage and fire
Installing fuses or breakers with a larger ampere rating than recommended for size of wire being protected destroys protection

13. ISI CODES IS No. DESCRIPTION IS 2705 CT for measuring and protection
IS Bus bar arrangement and marking
IS Meter (measuring)
IS Installation of Switch gear
IS Code of practice for earthing.
IS Selection, Installation and maintenance
of fuses upto 650V
IS Marking and arrangement of switch gear
Bus bar main Connectors and auxiliary
wiring.
IS Cubical Board.
IS Insulated conductor rating.
IS Enclosed distribution switchboard and
cutout for Voltage not exceeding 100 V.

14. IS 961 Miniature circuit breaker.
IS Fuse wire use in rewirable type electric
fuses upto 650V.
IS PVC insulated electric cable heavy-duty.
IS Aluminium conductor for insulated cable.
IS Recommended current rating for cable.
IS Code of practice for electrical wiring
installation system Voltage not exceeding
650 V.
IS Code of practice for wire safety of
building (general) Electrical installation.
  IS PVC insulated cables (wire). 
IS Rigid non metallic conduits for electrical
wiring.
IS Flexible (playable) non metallic conduit
for electrical Installation.

15. IS 1293 Three pin plugs and sockets.
IS Conductor for insulated electrical cables
and flexible codes.
IS Specification for conduit for electrical
installation.
IS Accessories for non metallic conduit for
electrical wiring.
IS Switches.
IS Plugs.
IS Capacitor.
IS General safety requirement for lighting
fitting.
IS Code of practice for lighting public
thorough fares.

16. IS 3528 Water proof electrical lighting fitting.
IS Water tight electrical lighting fitting.
IS Mild steel tubular and other wrought
steel pipe fitting.
IS Luminaries and street light.
IS HRC fuses having rupturing capacity of
90 KA.
IS Exhaust Fan.
IS Class – I Ceiling Fan.

17. ELCB AND MCB “MCB” is an acronym of Miniature circuit breaker
“ELCB” is an acronym for Earth Leakage Circuit Breaker.
This component is designed to detect electric current leakage in a house wiring and appliances connected to the wiring.
The leakage current (or leakage voltage) occurs because of defect in a part of the installation, which can be caused by faulty components or by injuries to the insulation of the wiring, cables, electrical appliances or other accessories such as the switches and socket outlets.
When there is leaked current that exceeds the preset value of the ELCB setting, the ELCB then breaks the connection of the incoming electricity supply from the internal house wiring.

18. A CLOSE VIEW OF MCB

19. MCB Characteristics

20. Advantages of MCB’s over Fuses
Tripped MCB readily identified even in darkness
Cannot be switched back on while fault exists – trip free mechanism
Enables supply to be restored immediately and easily even by untrained personnel
Accepted as a circuit isolator
Locking devices can be attached for maintenance purposes
Do not normally require replacement
‘Single phasing’ of motors is not an issue
Do not age in service
Tamperproof

21. An ELCB unit inside a house electric panel
A close-up view of the ELCB unit

22. Typical ELCB circuit
generation of ELCB design.

23. the ELCB was actually a voltage-operated device that was designed to detect a current leaking through the earth path of electrical equipment and appliances.
The circuit that you see here is actually a residual current devise (RCD), or residual current circuit breaker (RCCB).

24. Observe that the supply coil, the neutral coil and the search coil all wound on a common transformer core. On a healthy circuit the same current passes through the phase coil, the load and return back through the neutral coil. they will produce an opposing magnetic flux.
when there is fault or a leakage to earth in the load circuit, or anywhere between the load circuit and the output connection of the ELCB circuit, the current returning through the neutral coil has been reduced.
Then the magnetic flux inside the transformer core is not balanced anymore. The total sum of the opposing magnetic flux is no longer zero. This net remaining flux is what we call a residual flux.
The periodically changing residual flux inside the transformer core crosses path with the winding of the search coil. This action produces an electromotive force (e.m.f.) across the search coil.
The induced voltage across the search coil produces a current inside the wiring of the trip circuit. It is this current that operates the trip coil of the circuit breaker.
During tripping when a fault is detected, both the phase and neutral connection is isolated.

25. The test pushbutton and the test resistor are arranged and wired to provide a testing function for the ELCB circuit. This part of the circuit bleeds away a fraction of the running current from the phase coil, and sends it through the return coil.

26. HOUSE SINGLE LINE DIAGRAM

29. PLATE ELECTRODE EARTHING:
Earthing electrode shall consist of plate, not lessthan 600 mm x 600 mm x 12 mm thick. The plate electrode shall be buried as far as practicable below permanent moisture level but, in any case, not less than 3 meters below ground level. Wherever possible, earth electrodes shall be located as near the water tap, water drain or near down take pipe.
Earth electrodes shall not be installed in proximity to a metal fence. It shall be kept clear of the buildings foundations and in no case it shall be nearer than 2 meters from the outer face of the wall.

30. The earth plate shall be set vertically and surrounded with 150 mm thick layer of charcoal dust and salt mixture mm GI pipe shallrun from the top edge of the plate to the ground level. The top of the pipe shall be provided with a G.I. threaded cap for watering the earth through a pipe. The G.I. cap over the GI pipe shall be housed in a masonry chamber, approximately mm x mm x mm deep. The masonry chamber shall be provided with a cast iron inspection cover resting over a GI frame, embedded in masonry.

31. PIPE ELECTRODE EARTHING:
Earthing electrode shall consist of a CI pipe (class B of approved make), not less than 40 mm dia. and 3 meters long. CL pipe electrode shall be cut tapered at the bottom and provided with holes of 12 mm dia. drilled at 75 mm interval upto 2.5 meters length from bottom. The electrode shall be buried vertically in the ground as far as practicable below permanent moisture level, but in any case notless than 3 mtr. below ground level. The electrode shall be in one piece and no joints shall be allowed in the electrode. Wherever possible, earth electrodes shall be located close to water tap, water drain ora down take pipe.

32. Earth electrode shall not be located in proximity to a metal fence
Earth electrode shall not be located in proximity to a metal fence. It shall be kept clear of the building foundations and in no case; it shall be nearer than 2 meters from the outer face of the wall.
The pipe earth electrode shall be kept vertically and surrounded with 150mm thick layer of charcoal dust and salt mixture upto a height of 2.5 meters from the bottom. At the top of the electrode a G.I. threaded cap shall be provided for watering the earth. The main earth conductors shall be connected to the electrode just below the G.I. cap, with proper terminal lugs and check nuts. The G.I. cap over the CL pipe and earth connection shall be housed in a masonry chamber, approximately 300 mm length x 300 mm wide and 300 mm deep. The masonry chamber shall be provided with a cast iron inspection cover resting over a C.I. frame, embedded in masonry.