Electrical Work free electron atom free electron nucleus

Electrical Work free electron atom free electron nucleus copper wire (i. e. conductor) free electrons flowing in all directions positive electrons Simplified exploded view of a copper atom negative free electrons flowing in the same direction (an electrical current) bulb Battery and bulb circuit break the circuit and the current will cease to flow power source switch fuse battery cable 0. 5 ohm resistance Equivalent circuit diagram with meter installed From Plumbing (3 rd edition), R. D. Treloar, page 273 Basic electrical theory Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com

Electrical Work 4 V 4 V 4 V 12 V Electrical circuits in series 12 V 12 V Electrical circuits in parallel ammeter copper cathode (positive) dilute sulphuric acid zinc anode (negative) direct current alternating current (electron flow in one direction) R (electron flow back and forth) R soft iron core brown black grey black Production of direct current (principle of a battery) phase grey earth magnet grey brown black earth Single phase supply Electrical current (230, ~ 50 Hz) From Plumbing (3 rd edition), R. D. Treloar, page 275 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com Three phase supply (400 V)

Electrical Work 400 k. V power generating station 132 k. V national grid 33 k. V grid heavy industry substation 33 k. V subsubstation 33 k. V station 6– 25 k. V (3 phases and 1 common) either on poles, above or below ground substation light industry 11 k. V old red yellow blue black local substation 400 k. V main double pole switch (400 V between any 2 phases) industrial or 400 V commercial customer 230 V domestic customers neutral conductor cooker water heater lighting circuit station transformer new brown black grey blue super grid (to other power stations) downstairs ring circuit (RCD protected) 230 V circuit protective conductor meter Single and three phase connections from generator to consumer circuit breakers RCD or fuses main fuse concentric cable From Plumbing (3 rd edition), R. D. Treloar, page 277 Electrical supply Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com to equipotential bonding Consumer unit (fuse box) Domestic connection showing a TN-C-S system

Electrical Work tripping latch bi-metallic strip current flow magnetic trip coi MCB, cartridge and re-wirable fuse holders minimal amount of probe exposed Fused test lead proving unit to check operation of test equipment Approved test lamp Typical test meter and proving unit Locked off electrical circuits From Plumbing (3 rd edition), R. D. Treloar, page 279 Electrical safety Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com

Electrical Work consumer unit exposed structural steelwork 10 mm 2 cable meter 600 mm max gas meter main earth bar electrical supply water oil supply Equipotential bonding conductors Temporary bonding wire metal bath and basin taps Typical earth clip to BS 951 exposed metal pipework radiator metallic waste pipe Supplementary cross bonding Earth continuity From Plumbing (3 rd edition), R. D. Treloar, page 281 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com

Electrical Work 13 amp socket outlet 2. 5 mm 2 twin and earth PVC cable junction box N N E P spur outlet P E Ring final circuit neutral conductor NPE main double pole switch circuit breakers or fuses RCD 1. 5 mm 2 twin and earth PVC cable circuit protective conductor to simplify the illustration the earth has been omitted from the lighting circuit ceiling rose as switch is operated the contacts are made From Plumbing (3 rd edition), R. D. Treloar, page 283 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com bulb to next light note the lighting circuit does not return to the consumer unit 1 st floor landing switch 2 -way switching Lighting circuit Domestic house wiring 1 downstairs hall switch

Electrical Work 21 amp double polecpc (earth) switch with neon light indicator 2. 5 mm 2 twin and earth PVC cable neutral neon light 21 amp heat proof flex phase thermostat circuit breaker consumer or fuse unit 3 k. W heater element Typical radial circuit to an immersion heater thermostat earth (green and yellow heat proof flex or just green) live via the fuse (brown or red) dhw storage cylinder earth cable clamp heater element terminals fuse neutral (blue or black) Note: the second colour listed represents the old flexible cable colours cable Termination of cable to a plug From Plumbing (3 rd edition), R. D. Treloar, page 285 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com Immersion heater connection Domestic house wiring 2

Electrical Work conduit floor board cpc must be the last conductor to be disconnected should the supply cable be pulled from the appliance slotted joist conductors securely terminated Terminating cables at fixed appliances 50 mm min protection of cables in walls ceiling board 50 mm min Support of cables under floors Installation practices From Plumbing (3 rd edition), R. D. Treloar, page 287 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com cable not subject to undue stress steel conduit hole in centre line of joist to prevent weakening

Electrical Work power N supply L contacts bi-metallic strip brass contacts temperature adjusting screw Invar rod brass tube immersion heater element etc. (reduced in size) Invar steel terminals Bi-metallic strip temperature setting control Differential expansion terminals step down transformer contacts switch L capillary tube sleeve or pocket into appliance N Filament ignition hammer spring filament crystals Thermostats bellows earth pilot sensor filled with a electrode Liquid expansion volatile fluid step up transformer spark lead Piezoelectric ignition L pilot flame N Spark ignition Ignition devices Electric thermostats From Plumbing (3 rd edition), R. D. Treloar, page 289 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com Electrical components 1 Spark generator

Electrical Work primary windings soft iron core a. c. ~ input secondary windings terminals high voltage current output electro-magnetic Transformer force back and forth coil of wire (solenoid) armature low voltage current iron armature contacts yoke valve iron core a. c. Solenoid in out d. c. single diode rectifier Rectifier bridge rectifier a. c. Relay Should a low voltage pass through the coil the armature is drawn into the relay making the high voltage contacts d. c. insulating material capacitor fitted to c. h. pump metal foil plates Printed circuit board (PCB) Capacitor Contains many electrical components, such as a transformer, relay and capacitor From Plumbing (3 rd edition), R. D. Treloar, page 291 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com Electrical components 2

Electrical Work From Plumbing (3 rd edition), R. D. Treloar, page 292 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com

Electrical Work domestic circulator 3 -port mid-position motorised valve cylinder thermostat boiler programmer room thermostat junction box electrical supply Central heating wiring systems From Plumbing (3 rd edition), R. D. Treloar, page 293 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com

Electrical Work earth terminal phase or neutral terminal Testing for insulation resistance known earth (e. g. screw of plug outlet) insulation resistance tester exposed metal Multi-test meter digital multi-meter Testing for earth continuity Inspection and testing of electrical work From Plumbing (3 rd edition), R. D. Treloar, page 295 Copyright Blackwell Publishing Ltd, all rights reserved: www. blackwellpublishing. com Able to undertake a whole range of electrical tests, from insulation resistance to earth loop impedance