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How to Connect a Portable Generator to the Home Supply – 4 Methods

How to Connect a 1-P & 3-P Portable Generator to Home Supply with Changeover & Without Changeover or Transfer Switch (ATS & MTS)

We all suffer the power failure in emergency breakdown (i.e. short circuit, overload, damage to electric transmission lines, substations or other parts of the distribution system or storms and other bad weather conditions etc.) In this case, emergency generator can be used to restored the electric power to the home or other connected appliances.

In this step by step tutorial, we will be showing the portable generator wiring and connection diagram to the home supply and main distribution board. We will be using Automatic Changeover Switch also known as  Automatic Transfer Switch (ATS), Manual Changeover Switch (MTS or Manual Transfer Switch) to connect the generator to a house. In addition,  We may also wire a portable generator to home supply without changeover switch or transfer switches.

By using the following basic electrical wiring installation diagrams for generator connection, you may restore an emergency electric supply in case of power outage by connecting a portable generator (Gas/Petrol/Diesel Generator) to the main distribution board.

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So now let’s begin.

We can connect a portable generator to our home supply system by four methods.

Each method with wiring connection and working and operation has been explained in step by step tutorial. (Please read all cautions / warnings, user manual and care must be taken before, while installing a generator to the home electric power supply system.)

Important Note:

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 practical tutorial.

How to Connect a Portable Generator to Home by using Manual Changeover Switch or Manual Transfer Switch (MTS)?

Connecting a portable emergency generator to the home power supply system by using manual or automatic changeover swiches (Auto transfer Switch (ATS) is the the safest and recommended method.

Steps for Wiring & Installation of a Generator By using Manual Transfer or Changeover Switch

To connect a portable generator to the home electric supply system by manual changeover switch, follow the steps below:

  1. Install a Changeover switch (about 63-100A depends on the load) near main distribution board in the home.
  2. Connect the main power supply (Line and Neutral) as incoming to the first upper slots of Changeover Switch as shown in fig.
  3. Connect a 6 AWG (7/064″ or 16mm2)” cable wire to the lower two slots of Changeover switch.
  4. Now connect a 3-pin power socket to the 6AVG wire and install onto the wall (near to the generator) and put the generator 3-pin power plug into the power socket which you have installed before.
  5. You have done and ready to supply emergency electric power to the home appliances in case of emergency power blackout.

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Below are the wiring connection diagrams for generator wiring with the help of manual transfer or Changeover switch.

In case all the loads are connected to the generator supply in power outage.

Click image to enlarge

How to Connect a Portable Generator to the Home by using Manual Changeover Switch or Transfer Switch (ATS)
Fig 1 – How to Connect a Portable Generator to the Home by using Manual Changeover Switch or Transfer Switch (ATS)

If you want to connect specific load to the generator when utility power goes off i.e. some load on generator and the rest on main power supply as there may be a case where generator may not be able to handle the overall load.

Click image to enlarge

Generator Wiring Diagram to the Home Supply by using Manual Changeover Switch or Transfer Switch (ATS)
Fig 2 – Generator Wiring Diagram to the Home Supply by using Manual Changeover Switch or Transfer Switch (MTS)

How to Connect a 1-Phase Generator to a Home by using Automatic Changeover Switch or 2 Pole Manual Transfer Switch (MTS)?

In this way, We have to use a two poles (2P) automatic transfer or changeover switch to connect the generator to a home. The connection method is same as mentioned above for method 1, but we have to used single phase 2 pole automatic changeover instead of manual transfer switch. No hesitation in this way i.e. when the power restores from the utility, the auto transfer switch automatically detect the power and redirect from the generator supply to the main supply and vice versa.

Note: You may use Three Poles (3P) Changeover instead of 2 Poles as well.

Click image to enlarge

How to Connect a Generator to the Home by using Automatic Changeover Switch or Transfer Switch (ATS)
Fig 3 – How to Connect a Generator to the Home by using Automatic Changeover Switch or Transfer Switch (ATS)

How to Connect a Portable Generator to a Home without Changeover or Transfer Switch

The Installation process is same as mentioned above but without MTS (Manual Transfer or Changeover Siwtch). For this method,  switch off both the main switches (MCB) of main power supply and the Secondary MCB where generator has to be connected. Now, connect a Power inlet or 3 Pin Power socket  to the second MCB by using 6 AWG (7/064″ or 16mm2)”. Now connect the 3 pin power plug of generator in that power inlet or power socket (As shown in below fig). You have done!

The Blue Line (In fig 5, 6, 8 & 9) and arrows () shows the power flow in the circuit.

Click image to enlarge

How to Connect a Portable Generator to a Home without Changeover or Transfer Switch
Fig 4 – How to Connect a Portable Generator to a Home without Changeover or Transfer Switch?

Operation and Working

1. In case when utility power supply is not available:

In this case, generator supplies electricity to the home appliances and power flow will continue to those connected electrical appliances and devices through (the Red Line in the Blue rectangle box) by generator (as shown in below image).

The Red Line in the Blue rectangle box) and arrows () shows the power flow in the circuit.

Related Post: How to Wire Battereis in Series, Parallel and Series-Parallel?

Note: Please! Be Careful.

In this case, the first MCB (Main Switch which is connected to main power supply) would be “OFF” and the second MCB switch (which is connected to generator) should be “ON”. For extra safety purpose, Switch off the 3 Pin Power socket by switching OFF the button when generator is not in used.

Click image to enlarge

How to Wire a Generator to the distribution board
Fig 5 – How to Wire a Generator to the distribution board

2. In case when power supply restores from power house:

In this case, the main electric lines supplies electricity to the home appliances and power flow will continue to those connected electrical appliances in the system  through the (the Red Line in the Blue rectangle box) by main power supply from the power house. Thus, portable generator remains standby.

The Blue Line and arrows () shows the power flow in the circuit.

How to Hook up an Emergency Generator to the House
Fig 6 – How to Hook up an Emergency Generator to the House?

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Note: Please! Be Careful.

In this case, the first MCB (Main Switch which is connected to main power supply) would be “ON” and the second MCB switch (which is connected to generator) should be “OFF”. For extra safety purpose, Switch off the 3 Pin Power socket by switching OFF the button when generator is not in used.

Cautions And Warnings:

Only 1 MCB should be “ON” at a time. If the second MCB is “ON” in the above shown figures and operation, i.e. both MSBs switch “ON” at the same time. Then;

  1. When utility power restores from the power house , it may damage your generator or burn the whole system that can cause electric shock & hazard, dangerous fire and explosion at once.
  2. When main electric supply is not available, generator will send electric supply back into main cables and lines which may overload the generator and may electrocute those linesman & electricians who work/repair in other homes and utility power lines

Wiring of Portable Generator to Home Supply with Separate MCB

  • Please read all the given notes, warnings, instructions, manuals and cautions before implementing this method as it may not be legal in some countries due to safety and hazard. Also, It is not recommended for beginners and only a possible way for practical engineers and experienced technicians in case of very emergency (i.e power supply failure in hospitals during serious operations) and there is no alternative to restore the power supply.

This is quite simple (as well as dangerous) method to connect a generator to the fuse board with the help of 3-Pin Power wall socket and an additional MCB to quickly restore the power supply in case of utility power failure.

In case of power failure, just switch “OFF” the main switch (DP MCB) and simply connect the generator 3-pin plug into 3-Pin power inlet/ wall socket which is already installed in the home wiring system as shown in the below wiring diagram.

Click image to enlarge

Wiring of Portable Generator to Home Supply with Separate MCB
Fig 7 – Wiring of Portable Generator to Home Supply with Separate MCB

Operation and Working

The working and operation of method #3 is same like method #2.

1. In case when power supply restores from power house:

In this case, the main electric lines supplies electricity to the home appliances and power flow will continue to those connected electrical appliances in the system  through the (the Red Line) by main power supply from the power house. Thus, portable generator remains standby.

The Blue Line through the Line (Red) and arrows () shows the power flow in the circuit.

Note: Please! Be Careful.

In this case, the first MCB (Main Switch which is connected to main power supply) would be “ON” and the second MCB switch (which is connected to generator) should be “OFF”. For extra safety purpose, Switch off the 3 Pin Power socket by switching OFF the button when generator is not in used.

Click image to enlarge

How to Connect a Generator to the Fuse Board
Fig 8 –

2. In case when utility power supply is not available:

In this case, generator supplies electricity to the home appliances and power flow will continue to those connected electrical appliances and devices through (the Red Line) by generator (as shown in below image).

The Blue Line through the Line (Red) and arrows () shows the power flow in the circuit.

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Note: Please! Be Careful.

In this case, the first MCB (Main Switch which is connected to main power supply) would be “OFF” and the second MCB switch (which is connected to generator) should be “ON”. For extra safety purpose, Switch off the 3 Pin Power socket by switching OFF the button when generator is not in used.

Click image to enlarge

Connection of the Portable Generator to the Home with Separate MCB
Fig 9 –

Cautions And Warnings:

Only 1 MCB should be “ON” at a time. If the second MCB is “ON” in the above shown figures and operation, i.e. both MSBs switch “ON” at the same time. Then;

  1. When utility power restores from the power house , it may damage your generator or burn the whole system that can cause electric shock & hazard, dangerous fire and explosion at once.
  2. When main electric supply is not available, generator will send electric supply back into main cables and lines which may overload the generator and may electrocute those linesman & electricians who work/repair in other homes and utility power lines
  3. If you don’t have enough practical experience and not sure about the safety rules provided by the power supplier or generator user manual in you country, don’t practice this method to connect the portable generator to home supply system. It is also recommended to contact a licensed electrician or power supply company before implementing this method.

How to Connect a 3-Phase Generator to Home with 4 Pole Automatic Changeover Switch?

To connect a three phase portable generator to the home supply, We have to use a four pole (4P) automatic changeover or transfer switch. The connection method is same as mentioned above for single phase generator and changeover switch, but we have to used three phase 4 poles manual changeover switch. It is the most reliable and recommended way to connect a generator to the home supply because when the power restores from the utility, the automatic transfer switch automatically detect the power and redirect from the generator supply to the main supply and vice versa.

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Note: You may use Three Poles (3P) Auto changeover switch instead if Four Poles (4P) changeover or transfer switch.

Click image to enlarge

How to Connect a 3-Phase Generator to Home with 4 Pole Manual Changeover Switch
Fig 10 – How to Connect a 3-Phase Generator to Home with 4 Pole Manual Changeover Switch

How to Connect a 3-Phase Generator to Home with 4 Pole Manual Changeover Switch?

There is no big difference in wiring connections for automatic and manual changeover and transfer switches with portable generator. In the following wiring connection, we have used a four pole manual changeover switch to connect a three phase emergency generator to the distribution boards. The wiring connections for three phase transfer switch are same as wiring for single phase 2 pole changeover switch in method one, while there is another two slots for additional line and neutral as shown in fig below.

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Note: You may use Three Poles (3P) Manual changeover switch instead if Four Poles (4P) changeover or transfer switch.

Click image to enlarge

How to Connect a 3-Phase Generator to Home with 4 Pole Auto Changeover Switch?
Fig 11 – How to Connect a 3-Phase Generator to Home with 4 Pole Auto Changeover Switch?

Wiring Color Code:

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

NEC:

Single Phase 120V AC:

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

Three Phase 208 AC:

Black = Phase 1 or Line1, Red = Line 2, Blue = Line 3, White / Gray = Neutral and Green/Yellow = Earth Conductor

IEC:

Single Phase 230V AC:

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

Three Phase 208 AC:

Grey= Phase 1 or Line1, Black = Line 2, Brown = Line 3, Blue = Neutral and Green = Earth Conductor

General Precaution

General Precautions while playing with Electricity.

  • 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 instructions, user manuals, 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 read other Electrical Wiring Installation Tutorials.

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18 Comments

  1. All of these diagrams are dangerous and illegal and shouldn’t be published here. No one should ever connect a generator to the house in these ways. The only way is to use a changeover switch so that the mains is isolated whilst the generator is in use and visa versa. In other words, the switchboard is connected to the common side of the changeover switch and the mains connected to the input 1 and the generator to the input 2.

    1. i totally agree with Alan the way to go is either a auto change over or a mechanical change over either way it is no possible to have both supplies on at once

  2. Method 2 is almost right but there should be no wiring or connections to the top MCB’s.
    The mains power should come into the top of the changeover switch only and no wiring to anywhere else.
    Basicly you are interupting the mains power to the MCB’s by the changeover switch, when you switch it over, the power will flow from the generator to the MCB’s. Only one set of MCB’s is needed.
    In Australia, if you published or told a non qualified person how to wire up electrical equipment like this, you could be prosecuted if they were injured. Please remove all other methods, there is only one method, the manual or automatic changeover swith.

  3. I use 2 high power relays switching both L and N and have it so they are wired to automatically switch power source. This is wired with delay timers in the circuit to ensure clear separation of power supply when changing over and prevent accidentally making the Mains line live. You don’t want to kill the electrician working down line trying to fix the reason for the power cut in the first place. If you are going to have it manually switched you need to consider making it physically impossible to have both on.

    1. Tim, you don’t need a delay you need to electrically interlock each relay coil with each other so only one can energise as well as mechanicaly interlocking them so it is impossible to energise both.
      They do fail and I have worked on cranes with forward reverse contactors for years (relays) they do stick and jam on sometimes. Mechanical interlocks prevent this happening. The better way is to get a changeover contactor which is energised with the mains on with 2 normaly open contact and 2 normaly closed contacts. When the power fails, it drops out and the auxillary input is connected.

  4. Hi,

    Thank you very much for the information, By the way I have a question regarding the portable generators that I always power up my store unfortunately some times I found that when I switch on many things my generator sims to sound loudly and suddenly Shut down and offline. Please can you help me to rectify the fault.

    1. In my Case, (When I face this problem) I check the generator oil (engine lubricant) if they need to change, Check the spark plug if they need to clean/replace, Check the load (especially overload), make sure the gas/oil as input is connected and sufficient to run the generator. Finally contact the generator mechanic for overhauling.

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