BUILDING SERVICES

1. BUILDINGSERVICES ENGINEERING

2. ◾ Most domestic premises receive a single-
phase supply of electricity from an area
electricity board at a rating of 230 volts and
frequency of 50 hertz.
◾ The area electricity board's cable, from which
the domestic supply is taken, consists of four
lines, three lines each carrying a 230 volt
supply and the fourth is the common return
line or neutral.
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◾ Neutral is connected to earth at the
transformer or substation as a safety
precaution should a fault occur on the
electrical appliance.
◾ Each line or phase is tapped in turn together
with the neutral to provide the single-phase
240V supply.

4. ◾ The supply or intake cable may enter
building in two ways
I. Underground duct
II. Overhead supply.
◾ An underground supply is preferred since all
of the electrical service is hidden.
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◾ From the service cable, the supply passes through the meter,
which records the electricity consumed in units of kilowatthours.
◾ Then the supply passes through the fuse which protects the
distribution board when excessive currents flow in the system.
◾ The fuse consists of a piece of wire made of a metal or an alloy of
appropriate melting point, i.e, aluminium, copper, iron, lead, tin
etc.
◾ If a current larger than the specified value flows through the
circuit, the temperature of the fuse wire increases. This melts the
fuse wire and breaks the circuit.
◾ From the fuse, the supply is passed to the distribution board.
◾ The distribution board has a main switch to control (Switch off
and switch on) the circuit breakers (MCBs and ELCBs).
◾ These fuses are a protection against excess current or overload, the
fuse or circuit breaker will isolate the circuit from the source of the
problem.

10. Electric Meter
Electric meters use either digital displays or dials.
The difference between one month's reading and the next is the amount of
energy in kWh that have been used for that billing period.

11.  Electricity meters operate by continuously measuring the
instantaneous voltage (volts) and current (amperes) to
give energy used (in joules, kilowatt-hours etc.).
 Meters for smaller services (such as small residential
customers) can be connected directly in-line between
source and customer.
 For larger loads, more than about 200 ampere of
load, current transformers are used, so that the meter can
be located somewhere other than in line with the service
conductors. The meters fall into two basic categories,
electromechanical and electronic.

12. Electromechanical
 On a single-phase AC supply, the electromechanical induction meter operates
through electromagnetic induction .
 This is done by counting the revolutions of a non-magnetic, but electrically
conductive, metal disc which is made to rotate at a speed proportional to the
power passing through the meter.
 The number of revolutions is thus proportional to the energy usage.
Electronic meters
 Display the energy used on an LCD or LED display, and some can also
transmit readings to remote places.
 In addition to measuring energy used, electronic meters can also record other
parameters of the load and supply such as instantaneous and maximum rate
of usage demands, voltages, power factor and reactive power used etc.
 They can also support time-of-day billing, for example, recording the amount of
energy used during on-peak and off-peak hours.
 The meter has a power supply, a metering engine, a processing and
communication engine (i.e. a microcontroller), and other add-on modules such
as a real time clock (RTC), a liquid crystal display, infra red communication
ports/modules and so on.

13. MAIN SWITCH:
1. The main switch is connected in the live and the neutral wires.
2. It is used to cut the connections from the live wire and the neutral wire
simultaneously from the main supply.
3. The main switch is installed in the distribution board, from where the supply is
divided into sub-circuit through ELCBs and MCBs.
4. The main switch can be cut off by a human or a computerized system to control
the flow of power in the building.

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◾ The consumer unit should be fitted close to
the point of service entry and from here the
service is divided into a number of sub-
circuits.
◾ It is normal in a domestic installation to
separate power circuits and lighting circuits
so that if a fault occurs then not all socket
outlets or lights are isolated.

15. RECEPTION AND DISTRIBUTION OF MAIN SUPPLY
 There should be a circuit breaker or a linked switch on live
conductor of the supply mains at the point of entry.
 The wiring throughout the installation should be such that there is no
break in the neutral wire in the form of a switch or fuse unit.
 All main switches should be either metal clad enclosed pattern or of
any insulated enclosed pattern and should be fixed at close
proximity to the point of entry of supply.

16. SINGLE PHASE SUPPLY
All loads in a single phase installation are connected in parallel and
supplied at the same voltage.
Figure shows a simple diagram of a single phase installation.

17. The consumer’s main switch-fuse is connected after the meter and
feeds a distribution board.
A switch fuse is a composite unit, comprising a switch with the fuse
not being carried by the moving member of the switch.
A distribution fuse board consists of one or more fuses or circuit
breakers mounted on a distribution to and protection of one or more
sub-mains or final sub-circuits.

18. Panel Board:
 A distribution board (also known as panelboard, breaker panel, electric
panel, DB board or DB box) is a component of an electricity supply system .
 divides an electrical power feed into subsidiary circuits while providing a
protective fuse or circuit breaker for each circuit in a common enclosure.

 Normally, a main switch, and in recent boards, one or more residual-current
devices (RCDs) or residual current breakers with overcurrent protection (RCBOs)
are also incorporated.

19. The distribution board houses several electromechanical devices:
i. Main Circuit Breaker: This is the main electromechanical device that
can cut off power from the meter cable.
ii. Miniature Circuit Breakers (MCB): A miniature circuit
breaker controls the supply to various miniature circuits on the main
circuit. They switch off if they detect an overcurrent i.e. current that
supersedes the circuit’s current rating. They can be single-pole, double-
pole, triple-pole, and four-pole, based on the capacity of each circuit
and the required energy input of the appliances connected.
iii. Residual Current Circuit Breaker (RCCB): Put simply, RCCBs are
lifesavers, mandatory in many states’ electrical codes. They can detect
if the current is being leaked into a human body or into water (i.e. an
earthing fault), and then automatically switch off. They are highly
sensitive circuit breakers used in series with MCBs and can detect any
slight imbalance between the phase conductors.

20. iv. Molded Case Circuit Breaker (MCCB): These devices have the same
function as MCBs, except with a far higher current rating. This means it
has more versatility and can interrupt larger current ranges, allowing it to
be used in both residential and industrial applications.
v. Isolators: These are manually controlled electromechanical devices for
isolating a part of the circuit for maintenance. They are often used in series
with MCBs for when an MCB fails. Electricians use this to cut off the
current in a circuit so that they can repair the circuit without getting
shocked.
vi. Busbars: Busbars are copper or aluminum conducting strips that carry
a large amount of current from the incoming meter line to the various
circuit breakers in the distribution board.
vii. Switches: These are present on all circuit breakers and automatically
switch off in case of any detection in overcurrent and short circuits.
vi. Identification Labels: These stickers help name the different miniature
circuits based on the rooms they control, so that end users can understand
which switch they have to flip to turn off or turn on a specific section of the
house/unit.

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◾ An isolator is a mechanical device, which is
opened manually and is provided so that the
whole of the installation, one circuit or one
piece of equipment may be cut off from the
live supply.
◾ In addition, a means of switching off for
maintenance or emergency switching must
also be provided.
◾ In practice it is the aim to bring the Electrical
supply to the appliance with as small a loss of
voltage through the conductor as possible.
◾ This means that the wiring must have the
smallest resistance that is economical

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◾ To balance electrical distribution across the
phases, connections at each floor should be
spread between the phase bars.
◾ To prevent the spread of fire and smoke, fire
barriers are incorporated with the busbar
chamber at each compartment floor level.
◾ The chamber must also be fire stopped to the
full depth of the floor.

23. ND PHTGRPHY
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