Single Phase Electrical Wiring Installation in Home NEC & IEC

Single Phase 120V/230V Distribution and Panel Board Wiring in Home

Single Phase wiring installation is the most common wiring in residential buildings. In Single Phase supply (230V in UK, EU and 120V & 240V in the US & Canada), there are two (one is Line (aka Phase, Hot or Live) and the other one is Neutral) incoming cables from the utility poles to the kWh energy meter and then directly connected to the main distribution board (Consumer unit).

In this step by step tutorial, we will show how to wire a single Phase Consumer Unit Installation in home from Utility Pole to a Single-Phase Energy Meter & Single-Phase Distribution board and then How to connect Single Phase Loads in single Phase Wiring Distribution System in home electric supply system.

Before go in details, you will have to know what is a Single Phase and Three Phase Supply, their applications as well as the role of RCD, MCB, MCCB, CB, DB, MDB, Final and Sub Circuits, Fuses, Switches etc.which is already discussed in our previous electrical wiring installation tutorials.

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The following different levels of voltages are available for domestics (as residential) and commercial (as industrial) application in the US, Canada (following NEC and CNC) and UK, EU and other countries which follows the IEC e.g. India, Pakistan, UAE, KSA, Philippine, South Africa, Nigeria, Indonesia etc. The following fig at the end of this section will help you easily understand the difference between single phase and three phase voltage levels in the NEC and IEC.

In the USA, for single phase 120V and split phase or 240V, the secondary winging of the distribution transformer mounted on the utility pole is center-tapped i.e. two hot wires (Hot 1 and Hot2) and the center wire as Neutral. This way, the voltage level between Hot and Neutral is 120V single phase and voltage between two hots (Hot 1 & Hot 2) is 240V single phase.

Single Phase Voltage Levels in the USA

Three Phase Voltage Levels in the USA

i.e.

And

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In a Three Phase Wiring Distribution System (Star Connection i.e. 3 Phase, 4 Wire System); The power and distribution transformers may be wired in Star (Y) or Delta configuration). For example, the basic configuration for single phase and three phase system in the UK is 230V/400V where the primary of the distribution transformer mounted on the utility pole is connected in Delta Connection while the secondary is connected in Star or Y Connection.

This way, the Voltage between any phase and neutral is 230V single phase, while the voltage level between three lines are 400V three phase.

Single Phase Voltage Levels in the UK & EU

Three Phase Voltage in the UK & EU

I.e.

And

120V, 208V, 240V, 277V & 480V, Single Phase and Three Phase Supply Voltage Systems NEC US

120V, 208V & 240V High Leg Delta Configurations

230V & 400V Single Phase & Three Phase Power Supply Systems IEC UK & EU

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To Wire and install a single phase consumer unit for electric supply distribution in multi sections of a house, follow the steps given below:

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If you have to install a single phase mains distribution system in different sections around the home (large area), follow the following important things before doing so.

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Single Phase 120V & 240V Distribution and Panel Wiring in home.

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Single Phase 120V & 208V Distribution and Panel Wiring in home.

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Single Phase 120V & 208V & 240V (High Leg Delta) Distribution and Panel Wiring in home.

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Single Phase 277V & 480V Distribution and Panel Wiring in home.

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Good to know: it is against the code to use two separate single pole circuit breakers for 208V or 240V circuits. If you still want to connect two SP breakers as double pole for 240V circuit, the switches of both breakers should be bonded and connected together i.e. both SP breakers should be switched ON & OFF with the same common switch. In addition, use the proper rated breaker, wire size, outlets, and switches etc. (check the bottom note (instruction & precaution) for calculators and tutorials about wire size, sizing outlets, switches and socket etc.

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Single Phase 230V Distribution and Consumer Unit Wiring in Multi-sections of home.

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Single Phase, 230V Consumer Unit & Distribution Board Wiring with RCD

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Single Phase, 230V Split Load Consumer Unit & Distribution Board Wiring

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Single Phase, 230V Dual Split Load Consumer Unit & Distribution Board Wiring

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Good to Know: According to IET (Institution of Engineering and Technology) wiring regulations: 17th Edition (BS 7671:2008 1: 2011), an RCD protection must be provided in the consumer unit except smoke and burglar alarms system.

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There is no much difference in IEC and NEC wiring for single phase MCBs and associated wiring i.e. a single phase expect for 240V. In other words, 120V single phase load can be connected directly to the single pole MCB via three wires e.g. Black as Hot, White as Neutral and green with yellow stripe or bare conductor as protective ground.

In 240V single phase wiring, the load can be connected to the double pole MCB via three or four wires (as Neutral is always needed in that case and depends on the system design) i.e. Black as Hot 1, Red as Hot 2, White as Neutral (optional) and green/yellow stripe or bare conductor for ground wire.

Below are some typical single phase wiring diagrams used for power distribution in the home (United States of America and Canada).

Wiring Installation of Single Phase 120V Circuits & Breakers in Main Service Panel

Wiring Installation of Single Phase 120V & 240V Circuits & Breakers in Main Service Panel

Wiring Installation of Single Phase 120V & 208V Circuits & Breakers in Main Service Panel

Wiring Installation of Single Phase 120V, 208V & 240V (High Leg Delta) Circuits & Breakers in Main Service Panel

Wiring Installation of Single Phase 277V & 480V Circuits & Breakers in Main Service Panel

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For Single Phase Loads (230V or 120V) Washing Machines, TV, Power socket, Lighting Points, Fans etc., can be directly connected to the Phase and Neutral wire through proper wiring and controlling as shown below. Note that Earth or ground wire must be connected to each of the electrical appliances and equipment connected to both single phase and three phase supply systems to avoid electric shock and hazard.

Wiring single phase 230V load and MCB in the Distribution board and consumer unit with RCD.

Wiring single phase 230V Split Load load and MCB in the Distribution board and consumer.

Wiring single phase 230V Dual Split Load load and MCB in the Distribution board and consumer.

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Below is given layout wiring diagram of single phase consumer unit installation in a residential area.

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We have used Red for Phase, Live or Hot, Black for Neutral and Green for Earth/Ground Wire in the typical single phase wiring diagram. You may use the specific region or general practiced codes in the local area i.e. IEC International Electrotechnical Commission (UK, EU etc.) or NEC (National Electrical Code [US & Canada] see the detailed post about NEC & IEC wiring Color Codes where;

NEC USA:

Single Phase 120V AC:

Single Phase 240V AC:

Three Phase 208V & 240V AC (High Leg Delta):

Three Phase 277V & 480V AC:

IEC & UK:

Single Phase 230V AC:

Three Phase 400V:

For reference, here is the OLD UK Wiring Color Codes (Prior 2004) which still applicable in other countries i.e. India, Pakistan, UAE, KSA and other Arab Countries.

400V Three Phase

230V Single Phase

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You may also check the related Electrical Wiring Installation Tutorials.

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Single Phase Electrical Wiring Installation in Home NEC & IEC