Electrical wiring and safety

By Yogesh Joshi

Residential Circuits• Residential loads are connected in parallel,

since the voltage remains the same through the loads and if a circuit fails it does not affect the others

• Purelly resistor load (e.g. lights, toaster)– Demand P = VIcos(av – ai)– cos(av – ai) is the power factor

• If a motor is added (e.g. celing fan, refrigerator) – Demand Q = VIsin(av – ai), as well as P– sin(av – ai) is the reactive factor

Parallel wiring

Series Wiring

Sockets• A power socket is used for connecting

appliances.• Big hole specifies the neutral end (to source)• Small specifies the hot end (from source)• Examples

– 125V @ 15A– 125V @ 20A– 230V @ 30A– Ground Fault– Arc Fault

Switches• Switches allow the user to control a load (on/off)• Examples

– Single

– Double

– 3 way

– 4 way

– Toggle

– Pilot light

Cables• Black – hot, connection from the AC source to switch

typically• Red – return, connection from switch to load• White – neutral, connection from load back to the AC

source, it closes the circuit• Green – ground, protects people from electrically charged

metal parts

Color code

Size of Cables• 14 : minimum approved width in United

States for residential wiring. In PR we can use it for lamps wiring

• 12 : minimum approved width in Puerto Rico for residential wiring

• 2 : cable used from service panel to distribution panel, passes up to 100A of current

Size of Cables (cont.)

Service Panel• Nude cable comes from

transformer• It then changes to a white

cable and connects to the box

• From here a connection to breaker and ground is done

Distribution Panels• Load balancing: the act of distributing equally all 120V

loads

Safety measuresLive parts of electric equipment operating at 50

volts or more guarded against accidental contact by approved cabinets

Safety measures• Safety gloves And apron• Safety shoes• Safety Goggle• Proper insulated tools• Measuring equipments

Wire connectorsCrimping

◦Special Tool◦Approved Marine Connectors◦Use of Ratcheting Tool

Solder

Heat-shrink TubingTapping by cello tape

Wire connectors• Screw type connector

• Male-female connectors

AC & DC Protection • Ckt Breakers: work like a fuse,

opens current path when threshold is exceeded. This protects the circuits from high currents, no protection to people

• Ground connection: connection to ground so that users are protected from alternate current paths, like breakers they open the current path but when a current change is found

AC & DC Protection • Fuse • Covering on conductor• Signs warning of high voltage shall be

posted where other than qualified employees might come in contact with live parts

Ac &DC Protection• Must have source and return wires◦Return wires to a common point

◦May use feeder wire from power panel for: engine, helm console, etc.Wires above flood level of bilge◦Waterproof if in bilgeInsulated support every 18”Twist DC wires within 1 meter of compass• Portable ladders shall have nonconductive

side rails if they are used where the employee or the ladder could contact exposed energized parts

Effects of equipment on power distribution

• Burning• Heating • Fire • Explosion• Damage of equipment

References• http://www.healthyworkinglives.com/advice/workplace-hazards/electricit

y• https://www.google.co.in/search?

q=electrical+short+circuit+causes&espv=2&biw=931&bih=414&source=lnms&tbm=isch&sa=X&ved=0ahUKEwickI_PiKPQAhUFN48KHfxDDuAQ_AUIBigB&dpr=1.1#imgrc=9X5By7Ah5kfj0M%3A

• https://en.wikipedia.org/wiki/Category:Electrical_connectors• http://www.slideshare.net/jigsdbest/electrical-wiring-practices-and-

diagrams• https://www.google.co.in/search?

q=connector+are+used+for+cable&espv=2&biw=931&bih=458&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjDt5bpg6PQAhXJtY8KHdNjAYsQ_AUIBigB#tbm=isch&q=screw+connector&imgdii=be2jBXVcpWsf3M%3A%3Bbe2jBXVcpWsf3M%3A%3B1X1UTMwPMdd96

• Thanks…….