Section 1A - Module 1: Essential Electrics Flashcards
Electrical Associations
C&G
The City and Guilds of London Institute
UK’s main awarding body for a variety of qualifications. They are the provider of course programmes and exams for some of the electrical qualifications on this course
Electrical Associations
IET
The Institution of Engineering and Technology
Formerly the IEE (Institution of Electrical Engineers)
Publishers of the BS7671: The requirements for electrical installations
(Also now as the Wiring Regulations) a NON-STATUTORY document essential for anyone working in the electrical installation industry. It lays down the standards to be met for compliance with statutory legislation.
Electrical Associations
NICEIC
The National Inspection Council of Electrical Installation Contractors
(NIC for short) consumer led organisation who ensure quality and compliance of the work carried out by its enrolled contractors
Applicants must have been trading 6 months, comply with stringent requirements and allow annual inspection of their works.
Membership is often a deal maker for tendering contractors and deal breaker if not enrolled :/
Electrical Associations
ECA
The Electrical Contractor’s Association
Support company, to be eligible you must demonstrate financial stability and profitability for a minimum of 3 years.
ECA underwrites their enrolled members works if a contractor is unable to fulfil their work obligation so makes it attractive for a customer.
Electrical Associations
JIB
The Joint Industry Board
Two strands: Electro-technical/Plumbing
Union whose membership is not really prescriptive. Prior to Part P it was the only organisation to offer a graded register of electricians based on levels of qualification, knowledge, experience and expertise.
Electrical Associations
CITB
The Construction Industry Training Board
CITB are an industry recognised certification body that accredit approved centres that meet their high standards
These centres are regularly monitored to ensure they are achieving a high standard and show continued compliance.
Building Regulations Overview Part 1
The first set of ‘building regulations’ were introduced in 1965 and they have been amended and updated over the years with the latest fully updated version as the ‘Building Regulations 2010’
THE BUILDING REGULATIONS ARE LEGAL REQUIREMENTS approved by the Secretary of State.
They are based on the building act 1984 and provide a practical guide to help meet that acts requirements (Regulation 7 of the Building Act 1984)
Building Regulations Overview Part 2
The Building regulations:
- Are approved by parliament
- Deal with the minimum standards of design and building work for the construction of DOMESTIC, COMMERCIAL, and INDUSTRIAL buildings
- Set out the procedure for ensuring that building work meets the required standards
- Are designed to ensure structural stability
- Promote the use of suitable materials to provide adequate durability, fire and weather resistance, and the prevention of damp
- Stipulate the minimum amount of ventilation and natural light to be provided for habitable rooms.
- Ensure the health and safety of people in and around buildings (by providing functional requirements for building design and construction).
- Promote energy efficiency in buildings
- Contribute to meeting the needs of disabled people
Approved Documents (Building Regulations) Part 1
Each of the sections in the Building regs is covered by ‘Approved Documents’
These documents cover the practical application of the Building regs and how the requirements for each part CAN be met. The practitioner doesn’t necessarily have to do things as per the documents as long as the requirements for safety are met in the work carried out.
Approved Documents (Building Regulations) Part 2
Approved Documents are split into part:
A - Structure
B - Fire Safety
C - Site prep resistance to contaminants and moisture
D - Toxic substances
E - Resistance to the passage of sound
F - Ventilation
G - Sanitation, hot water safety and water efficiency
H - Drainage and waste disposal
No document I
J - Combustion appliances and fuel storage systems
K - Protection from falling, collision and impact
L1A - Conservation of fuel and power in new dwellings
L1B - Conservation of fuel and power in existing dwellings
L2A - Conservation of fuel and power in new buildings other than dwellings
L2B - Conservation of fuel and power in existing buildings other than dwellings
M - Access to and use of buildings
No document N
No document O
P - Electrical safety
Q - Security in dwellings
R - Physical infrastructure for high speed electronic communications networks
Approved Document 7: Material and workmanship
Building Regs and Approved Docs
PART P - Origin and purpose
Part P was introduced in January 2005 to provide a means of ensuring that any electrical work undertaken in domestic premises is carried out safely and correctly, and is tested, documented and notified by a competent person.
Building Regs and Approved Docs
PART P - Certification
City & Guilds 2393
Work done needs to be certified and made known to the client and building control office
Part P applies to electrical installations in buildings or parts of buildings. Specifically:
- Dwellings houses and flats
- Dwellings and business premises that have a common metered supply - such as shops and public houses having flats above them that are served by a common meter.
- Common access areas in blocks of flats such as laundries and gymnasiums.
Part P also applies to parts of the above electrical installations:
- In or on land associated with the buildings - such as fixed lighting and garden pond pumps.
- Outbuildings such as sheds, detached garages and greenhouses
Part P - Self certification
In order to self certify domestic electrical installation works you must be registered with a competent persons scheme operator or be directly employed by a company who are Part P registered and appear on the company register as being competent to undertake such works whilst in their employment.
(NOT COVERED FOR PRIVATE JOBS IF EMPLOYED BY A COMPANY))
Self certification continued, Registration Providers and Costs
Requirements:
- Proof of technical competence (Part P full Scope)
- Library of technical reference materials inc:
BS7671 IET Wiring Regulations
The Electricity at Work Regulations (EAWR) 1989
Copy of the Part P (advisable) - Evidence of your competence to do jobs (show previously completed work)
- Ability to use test instruments and complete electrical installations and minor works certificates correctly
- The condition and appropriateness of test instruments
- Public liability insurance (minimum £2 million)
- Written copy of your complaints policy
- Written copy of your health and safety policy
Part P Scheme operators
Blue Flame Certification
ELECSA
NAPIT Certification Ltd
Certsure LLP
STROMA
BESCA
OFTEC
Principles of Electricity 1
SI units
C J Ω V W A
C - Coulomb - Charge J - Joule - Energy Ω - Ohm - Resistance V - Volt - potential difference W - Watt - Power A - Ampere - electric current
Principles of Electricity 1
Conductor
A material that permits the flow of current
Metal
Principles of Electricity 1
Insulator
A material that prevents the flow of current
Ceramic
Plastic
Rubber
Principles of Electricity 1
Line and Neutral Conductor
Like water, electricity needs somewhere to flow around, a CIRCUIT. It needs to start from a source and in an electrical domestic situation this is the energy meter. The electricity flows outwards using the LINE (or live) conductor, powers the various appliances in the home then returns to the unit via the NEUTRAL conductor.
Both LINE and NEUTRAL are technically LIVE so ‘LINE’ is used to distinguish between the two.
Principles of Electricity 1
Amperes
1 ampere = 6.24 x 10 to the power 18 (more easily called a Coulomb) ELECTRONS (negatively charged particles) flowing through a certain point. (Interesting but not relevant.
Suffice it to say that an Amp is a measure of the amount of electrical current or electron flow through a certain point.
Electrons are repelled by each other and when given a push, the conga through a material like metal to create a flow.
Principles of Electricity 1
Amperes relative reference
1na - 1ya = Tiny currents in the antennae of your mobile 10ma = TV remote control 50ma = Keyboard and mouse 1A = High powered torch 3A = Typical laptop 15A = Microwave oven, vacuum cleaner 10,000+A = A bolt of lightening
Principles of Electricity 1
Conventional current Vs Actual Electron flow
Conventional current is the mistake that scientist made assuming that current flowed from positive to negative. Actual electron flow is from negative to positive with the electrons. All engineering is based on the conventional current (cue eye roll).
It’s cool though. All the math still works.
Principles of Electricity 1
Voltage (this is mind boggling)
Volts push current around an electric circuit (which is measured in Amps)
Voltage refers to difference in electrical potential energy, per unit of charge, between two points!!
Potential energy (measured in joules) = ability to do work (moving, heating etc) Unit of Charge = Coulomb (easier way of saying that huge amp number of electrons) THEREFORE 1A = 1C per second and 2A = 2C per second etc (much neater)
So…a certain number of joules of energy are being transferred for every unit of charge that flows.
EXAMPLE: Battery (1.5V) - Cable carries coulomb of charge (1.5 joules of energy) - this electrical potential energy pushes joules to the bulb - bulb emits 1.5 joules of heat and light
1V = 1Joule per Coulomb
Voltage is actually the measure of potential difference between two points. On a battery it’s the difference between the negative and positive terminal
(Interesting that Voltage can also be used to create communications by toggling between a low voltage and no voltage to create a binary code that carries no current but can be decoded by another device!)
Principles of Electricity 1
Ohms
Ω - Ohms - R
This is the circuits impedance or resistance
“The current flowing through a circuit under constant temperature conditions is directly proportional to the applied voltage and indirectly proportional to the total effective resistance of the circuit”
V=IR
I=V/R
R=V/I
Principles of Electronics 1
Power (P) or Watts (W) and Energy (E)
Watts is a small unit of measurement that measures the rate at which heat is given off by the circuit when electricity is converted.
Power (P or W) = Volt (V)x Current (I or A)
E.g. An electric fire drawing a 10A current from a 230V supply would dissipate 2300 Watts of power
P = VxI Therefore. 230 x 10 = 2300
The power rating of an electrical appliance (Wattage) may be found along with its working voltage, model number etc on its rating plate
(Most appliances are give a kiloWatt (kW) rating because the wattage is such a small unit.
2300 / 1000 = 2.3kW
Energy is a measure of the amount of power dissipated by a circuit and the time for which it operates - kWh - Kilowatt hour
Energy = Power x Time
Electric fire operated for 3 hours
E = PxT E = 2.3 x 3 = 6.9kWh
Principles of Electronics 1
Power loss, voltage drop and overheating
As current overcomes the resistance in a cable or device, heat is created.
Power is lost along the whole circuit and this causes the voltage to drop.
This can be minimised by using the correct cable with a sufficient CROSS SECTIONAL AREA (CSA) which will offer less resistance to the current.
Having too long a run with too small a cross sectional area will cause overheating and potential damage. Shorter runs are best and larger cables carry bigger current.
Principles of Electricity 1
Sources of Electricity and circuit theory
Mechanical/Chemical
AC/DC current
Mechanical electricity is what supplies our homes. It’s driven by steam to spin electromagnets which produce electricity (More on this in Electric supply section)
Chemical is associated with a battery supply of voltage
In both instances the battery or mechanical source create an ‘Electromotive Force’ (EMF) which drives current around a circuit. The Voltage or ‘potential difference’ pushes electrons around the circuit as a current which operates the motor, light bulb, circuitry.
In the case of a battery the current is DC - Direct Current, the electrons all flow in one direction.
AC
Ac stands for alternating current and is found in the majority of industrial, commercial and domestic properties. The usual voltage is 230V 50Hz where Hz denotes the amount of times per second (frequency) the current reverses direction.
Owing to the the dangers associated with AC at this voltage, it is a requirement that the neutral conductor is connected to earth at the supply transformer.
Principles of Electricity 1
Ohms Law and Resistivity
Resistivity is a materials natural resistance to the flow of a current
We can calculate the resistance of any given material from the equation
R = PI/a
P = Resistivity constant for the material (Ωm) L = the length of the material (m) A = the cross sectional area of the material (m2)
Resistivity values examples:
Material Resistivity (Ω m) Silver 16.4x10power-9
Principles of Electronics 1
Fuses 1
Why and how?
Fusing is a safety measure that aims to prevent high electrical currents from passing through circuits not designed to carry them.
Their basic design is that they contain fuse wire which melts or ‘blows’ when the current is too high and therefore breaks the circuit before any more damage can be done.
Principles of Electricity 1
Fuses 2
Fuse Types
Cartridge - MCB’s - Rewireable - High Breaking Capacity
MCB’c or Miniature Circuit breakers are also used and they ‘trip’ and are re-settable. You see these in newer domestic consumer units.
Cartridge fuse - little glass body with silver end cap with fuse elect inside
High Breaking Capacity Cartridge fuse - body with little metal rage at either end, it has a quartz filler inside
Re-wireable Fuse - looks like a brass holder in a plastic casing. Screws secure the fuse element
Principles of Electricity 1
Fuses 3
Fuse rating
Nominal current of protective device
Frequently in domestic properties, fuses are overrated. The following formulae will ensure we find the correct rating
I=P/V Or A=W/V
So a 100W Light bulb on a 230V circuit would = 0.434 A and would only need a 1Amp fuse. Most often a 3 would be fitted but some people in ignorance would use 13A. Having a higher rated fuse means that the circuit could heat up way too much before anything is caught, thus damaging the cable/equipment.
REMEMBER!!! The fuse protects the circuit, the earth protects you!!
Principles of Electricity 1
Circuits
Series and Parallel 1
Series
This is where a circuit is made from the EMF (a battery for example) to device (bulb) to device to device back to EMF.
The level of current flowing through the circuit will be the same at any point in the circuit. The supply voltage will divide across each component and will be proportional to the resistance of that component
If each lamp has the same resistance the same voltage will be ‘dropped’ across them. If they have different resistances, the voltage will be proportional, the bulb with the highest resistance will receive the highest voltage. In each case, the voltage dropped across each component will only add up to the source voltage. Eg. 12V battery supply, 3 bulbs at the same resistance would each require 4 volts to be dropped across each.
Principles of Electricity 1
Circuits
Series and Parallel 2
Parallel
In a parallel, each component is connected across the terminals of the supply therefore each component receives the same as the supply voltage.
NB. Dave’s interpretation here:
Whereas in a series, the voltage changes depending on the resistance of the component, in a parallel, the voltage is the same across all component but the current splits between each of the parallel branches depending on the level of resistance for each component.
All the different branch currents when added together will be the total current pulled from the supply.
Most things are wired in parallel because there is less risk of multiple components failing if one thing goes wrong.
Basic Domestic Circuits
Quick definition
Lighting
Ring Final Circuit
Radial
Lighting is a radial design (radial like the suns rays, reach out from a central hub and do not return)
Ring Final Circuit is a literal ring of circuit that returns to the consumer unit
Basic Domestic Circuits
Lighting specs
There is usually a radial lighting circuit on each floor of a domestic property
These are usually covered by a 6A rating and are either a 1.0mm or 1.5mm PVC cable
Details regarding the design are covered in BS7671 section 559 ‘Luminaires and lighting installations’ and appendix 4 ‘current carrying capacity and voltage drop for cables’ which will speak to the specifics of the rating needed for the fuse or MCB if they deviate from the standard
Basic Domestic Circuits
Ring Final Circuit
The sockets in domestic premises will usually be BS 1363 13A sockets.
Mostly in a ring circuit design although for some properties and situations, a radial circuit might be more suitable.
THE SIMPLEST WAY TO IDENTIFY A RING OR RADIAL CIRCUIT IS TO LOOK AT THE PROTECTIVE DEVICE SUPPLYING IT a ring will have two conductors whereas a radial only one. If there are three conductors then a spur has been taken from the consumer unit
Specs: traditionally wired in 2.5mm PVC but again each circuit must be designed in accordance with appendix 15 Regulation 433.1 in appendix 4 of BS7671
(Reg 411.3.3 required that all socket outlets normally accessible to ordinary persons MUST be protected by means of a 30mA RCD. This requirement includes cooker control units incorporating a 13A socket.
Basic Domestic Circuits
The Spur
A spur is an addition to a ring final circuit in the way of an extra socket or even lighting circuit
A spur is a cable which is either connected directly to the ring circuit conductors (non fused spur)
Or
By means of a fused connection unit (FCU) - (fused spur)
Basic Domestic Circuits
The Spur
Non fused
A non fused spur must be wired with the same size cable as the ring circuit and may provide one single or one double socket outlet or one item of permanently connected equipment.
You can wire it up in one of three ways
1) from a socket on the circuit
2) From the consumer unit
3) by use of a joint box
Basic Domestic Circuits
The Spur
Fused
The FCU must be wired in the same way as a socket outlet, two conductors in each terminal, the spur itself is then wired into the load side of the FCU.
The cable size and fuse should suit the need. For example if it was a lighting circuit a 1.5mm cable (the smallest permissible in an FCU ) with a 5A fuse would be in order. FCU’s are available in switched and non switched versions
Main Protective Bonding and Supplementary Bonding
It is a requirement of BS7671 that all extraneous conductive parts (gas, water, oil, structural steel work etc) are bonded together and are connected to the main earthing terminal (MET) in or nearby the main Consumer Unit (CU)
Why?
To minimise the possibility of dangerous potential differences existing between extraneous parts should a fault occur
This bonding together is called ‘equipotential bonding’
In some parts of the property, ‘supplemental bonding’ may be required where there are pipes that have become separated from the main sources, eg a bathroom water pipe was extended with plastic piping leaving a portion of metalwork unbonded.
EARTH CLAMPS should be used when connecting bonding conductors to pipe work. These are designed to provide low resistance connections and to clearly inform the occupants how important the connection is for their safety. SAFETY ELECTRICAL CONNECTION: DO NOT REMOVE
Safety
Circuit Protection
Safe Isolation
Circuit Protection - BS7671 requires that a circuit is disconnected automatically should a current greater than for which it was designed (over current) flow through it.
