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Single Phase Electrical Wiring Installation in Home – NEC & IEC

How to Wire a Single Phase Distribution Board & Consumer Unit in Home

Single Phase wiring installation is the most common wiring in residential buildings. In Single Phase supply (230V in UK, EU and 120V in US, Canada), there are 2 (one is Line (Live) and the other one is Neutral) incoming cables from the utility poles to 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 Single Phase and Three Phase Supply, their different and applications as well as the role of RCD, MCB, MCCB, CB, DB, MDB, Final and Sub Circuits which is already discussed in our previous electrical wiring installation tutorials.

Related Wiring Tutorials:

Requirements for Single Phase Wring Installation in Home

Required MaterialsNumber
Single Phase Energy Meter1
Two Pole MCCB: 63A to 100 A1
Double Pole: 63A, 30mA Trip Current RCD3
Double Pole MCBs: 63A3
Single Pole MCBs: 20A6
Single Pole MCBs:16A3
Single Pole MCBs: 10A6
Distribution Board Cases3
Copper strips for MCB common connection 3 (Cu Busbar segment)
Copper strip Busbar for Earth & Ground Link1 (Cu Busbar segment)

How to Wire Single Phase Main Distribution Board?

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

  • Connect the Incoming Live and Neutral (L and N) wires from the electric utility pole to the Single Phase Energy meter. If you are not sure how to do it, here is a step by step tutorial on How To Wire a Single Phase Energy meter).
  • Connect the Incoming Live and Neutral (L and N) Wires to the 2 Pole Moulded Case Circuit Breaker “MCCB” as shown in fig 1. It will be used as a main switch for all sections in the home.
  • Connect the MCCB to the Double Pole MCBc, RCD, Single Pole MCBs respectively for each sections and the outgoings wires and cable to the sub circuits and final sub circuits. Do the same steps for each section (3 Switch boards in our case). Keep in mind that proper connection should be done for Neutral and Live wires in the whole system as shown in fig 1. If confused, wiring color codes for IEC and NEC are given below in the info section for both single phase and three phase wiring.
  • Now, Connect the electrical devices and appliances with the Earth link terminal which leads to earth electrode in the earthing and grounding system as shown in fig 1.
  • Do the the same steps for all three distribution boards in different.

Related Post: How to Find the Rated Cable & Wire Size for Electrical Wiring Installations

Click image to enlarge

Single Phase Electrical Wiring Installation in Home – NEC & IEC
Fig 1: Single Phase Electrical Wiring Installation in Home

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

  1. As we shown in the fig 1, use separate main breaker and boards for each sections (3 different sections in our case). This way, electric supply would not interpreted on other section if one of the CB or MCB trip due to some reasons (Short Circuit etc). The whole system will go off at once if we connect each section loads (Fans, Light etc) directly to the main distribution board.
  2. If we use single circuit instead of three circuits for each section, high current will flow through the whole circuit if load of a single section increased which cause to overheat the cables. So there may be a risk of electric fire and hazard as well due to overheated cables In the building. Moreover, due to more current flowing in the cable, voltage drop may be increased and there the appliances and devices may not get the proper and rated voltage, so they might not work properly.
  3. Use the proper cable size and rated main breaker. In other words, The main breaker should capable to handle to load of all sections around the home. The same should be done for DP and SP breakers in sub distribution board which should handle the load (Lighting points , washing machine, fans etc) of desired section for sub and final sub circuits.

Electrical Wiring Color Codes of NEC and IEC

Wiring Color Codes:

We have used Red for Live or Phase , Black for Neutral and Green for Earth Wire. You may use the specific area codes i.e. IEC – International Electrotechnical Commission (UK, EU etc) or NEC (National Electrical Code [US & Canada] where;


Single Phase 120V AC:

Black = Phase or Line, White = Neutral and Green/Yellow = Earth Conductor


Single Phase 230V AC:

Brown = Phase or Line, Blue = Neutral and Green = Earth Conductor

Single Phase Electrical Wiring Installation Diagram According to IEC Color Code

Click image to enlarge

Single Phase Electrical Wiring Installation Diagram According to IEC Color Code
Fig 2: Single Phase Electrical Wiring Installation Diagram According to IEC Color Code

Single Phase Electrical Wiring Installation Diagram According to NEC Color Code

Click image to enlarge

Single Phase Distribution Wiring According to NEC Color Code
Fig 3: Single Phase Distribution Wiring According to NEC Color Code

Good to Know

In a Three Phase Wiring Distribution System (Star Connection i.e. 3 Phase, 4 Wire System);

Line to Line Voltage = 415V AC (208V in US) Three Phase System

Line to Neutral Voltage = 230V (120V in US) Single Phase System


  • L1 to L2= 440 V
  • L2 to L3= 440 V
  • L3 to L1= 440 V


  • L1 to N = 230 V
  • L2 to N = 230 V
  • L3 to N = 230 V

in USA and other Countries

  • L1 to L2= 208V
  • L2 to L3= 208V
  • L3 to L1= 208V


  • L1 to N = 120V
  • L2 to N = 120V
  • L3 to N = 120V

Related Post: How to Connect a Portable Generator to Home Supply System (Three Methods)

Wiring Diagram of single Phase Distribution Board In Home

Below is given layout wiring diagram of single phase consumer unit installation.

1 Phase Electrical Wiring Installation in Single and Multi-Story Building
Fig 4: 1 Phase Electrical Wiring Installation in Home

How to Connect Single Phase Loads in a 1-Phase Wiring Distribution System?

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 system to avoid electric shock and hazard.

How to Connect Single Phase Loads in a 1-Phase Wiring Distribution System?
Fig 5: How to Connect Single Phase Loads in a 1-Phase Wiring Distribution System?

General Precautions

  • Electricity is Our Enemy, if you give it a chance to kill you, Remember, they will never miss it. Please read all caution and instruction while doing this tutorial in practical.
  • Disconnect the power source before servicing, repairing or installing electrical equipments.
  • Ue the proper cable in size with this simple calculation method ( How to determine the suitable size of cable for Electrical Wiring Installation)
  • Never try to work on electricity without proper guidance and care.
  • Work with electricity only in presence of those persons who has good knowledge and practical work and experience who know how to deal with electricity.
  • Read all the instruction and cautions and follow them strictly.
  • Doing your own electrical work is dangerous as well as illegal in some areas.Contact the licensed electrician or the power supply company before practicing any change in electrical wiring connection.
  • The author will not be liable for any losses, injuries, or damages from the display or use of this information or if you try any circuit in wrong format. So please! Be careful because it’s all about electricity and electricity is too dangerous.

You may also check the related Electrical Wiring Installation Tutorials.

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  1. Enock samuel says:

    nice theory.but i need to know measures after installation

  2. ebai richard says:

    What is the best practice to wire a 3 bedroom apartment with two toilet, a kitchen, a seating room and 4 outdoor security lamps. However i will like to know the how many circuit braker and ratings that will be needed for, lamps, sockets, 2 water heater, etc
    Thanks in advance and looking forward to hearing from you.
    Ebai Richard
    Whatsapp: +237679340379

  3. Robert Krueger says:

    Have need of a circuit to control 3 d.c. air horns with 3 separate n o switches with 1 common power supply. Any switch can turn on all horns at same time. Also could use a single timer to control horns but also must be able to be as an emergency alarm system. And have a command switch from the front office to override all in paralel. Any other questions- my phone is 951-858-3242 i am maintenance leadman at a manufacturing plant.

  4. Anonymous says:

    How do we calculate the number of single pole MCBs and double pole MCBs to be used for a wiring installation?

  5. Srinivasa Rao Ravinuthala says:

    Dear Sir,
    You are giving very good knowledge useful for electrical family.I request you to please send electrical technology subject to my mail also.

  6. Fakhreddin says:

    I want a book tutorial for single and three phase home wiring

    1. Noge sebaeng says:

      Toss information will our learners very important

  7. Fakhreddin says:

    Hello this theory is very important and very nice

  8. Hi, how do I connect the wires from the lower changeover slots to the main db?

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