Monday, October 10, 2016

3 Phase Wiring Installation In Multi Story Building

In house wiring, we install two types of wiring in which one 3 phase wiring installation for house and other one single phase installation. In this post you will learn how to install three phase electrical wiring using a simple diagram in which i shown how to install three phase 4 wire system in a multi story building. One thing more that i shown 3 distribution boards in which every story have there own electrical main distribution board.

3 Phase Wiring installation In Multi Story Building / House

The three phase 4 wire system installation in home is very simple but to understand you must study each part of this class and devices which i use in the below diagram. I start from this from step one.

Utility Pole 3 Phase 4 Wire System

In the diagram is start from the utility pole and i get service line supply from utility pole to 3 phase kWh energy meter. This utility pole connect to step down transformer (supply from sub station). My means that the pole supply comes from the substation or step down transformer.

3 Phase kWh Energy meter

I also shown the wiring diagram for there phase 4 wire system kWh (kilowatt-hours) meter, I also published a post about the wiring and installation of three phase four wire system kWh energy meter. So kindly read the below article if you did not understand the method of 3 phase kWh energy meter connection.

Also read
How to wire and install the 3 phase kWh energy meter?
How to wire Single phase kWh meter?

4 Pole MCCB Breaker

After the connection of energy meter, i connect the 3 Phase 4 wire power supply to the MCCB (module case circuit breaker). However if you can do this connection then read the below post.
Also read
How to wire 3 Pole or 4 Pole MCCB Breakers?

Now come to the connection for distribution board for one story. The method of installation 3 phase wiring is simple, you divide your load in three parts and each part have there own Line (phase). My means that divide your load in 3 parts and provide one one phase to each part.
Now here i have multi story building in which each story have there own single phase distribution board.
So we will provide one one phase or line to each story. And our neutral will be common but this will be common in circuit breaker output point and each story have there own neutral wire. So provide my Line 1 or phase 1 to the first distribution board and you can see in diagram. So come to Distribution board.

Distribution Board Wiring Connection

In the db board, i use the following electrical devices.

Double Pole MCB Circuit Breaker 63 Amps

I get phase and neutral wire from the main circuit breaker( 4 pole MCCB) and connect to double pole MCB (miniature circuit breaker). Note that double pole MCB will be consider a main circuit breaker for single phase distribution board for below diagram.

Also read below
How to wire double pole MCB breaker?
How to wire and install single , double , three and four pole MCB (miniature circuit breakers)?

RCD Brekaer.
I also install and wire double pole RCD (residual current device) in each distribution board. If you did not understand the wiring and installation of RCD then read the following post.

Distribution Electrical board Wiring for Single phase
How to wire and Install the double pole RCD breaker?
How to wire a 4 pole RCD circuit breaker?

Earthing or Ground connection

I also done the earthing connection in 3 phase wiring installation diagram in multi story house. I shown this connection by using a earth symbol and green wire. In the below diagram the earth symbol consider as earth electrode.

Also read
How earthing system works for protection?

AC Voltmeter Wiring connection for single phase

I also do the voltmeter wiring connection is each distribution board and you can see it in diagram. However here is some post which help you more then this. (Note that the VM denote the ACV voltmeter in below diagram.

Also read
How to wire a voltmeter for single phase?
How to wire a voltmeters for Three phase?
How to wire voltmeter selector switch for 3 phase with volt meter?
How to install the volt meter selector switch for 3 phase 4 wire system?
How to wire light indicator for 3 phase 4 wire system?

Ampere meter / Ammeter connection with CT (current transformer)

I also shown the ammeter connection with current transformer in 3 phase installation diagram for multi story house. The connection of CT is simple with ammeter but this will be better for you if you read the following articles.

How to wire a ammeter for AC and DC?
How to wire ammeter with current transformer?
How to do digital ampere meter connection with CT Coil?

Complete Explanation of Three - 3 phase wiring installation in a multi story building

The installation of three phase 4 wire system in multi story building is simple if you want to use single phase supply for each story. Note that by doing this type of connection you must wire 4 distribution board where one for main MCCB circuit breaker and other for each story. And you can also do these connection in a single main DB but you must use a big size  distribution board box where you can easily install all circuit breakers. But if use there own distribution board in every story then this will be better option.

So let's do it step by step.
In the 3 phase wiring diagram i shown a utility pole from where i get service line connection for 3 phase kWh meter (energy meter). Now i connect the supply wire Red, Yellow , Blue and Black to the energy meter input connection terminals and get supply from energy meter out going connection to load.
One thing more that that we use color code of red yellow and blue when we are doing the three phase wiring but when it's come to the 3 phase four wire system, we use the black for neutral. And when we are gonna to doing connection of single phase ( current between phase and neutral) then we use red for phase (hot wire) and black for neutral.

After the connections of three phase kWh meter we provide the 3 phase 4 wire supply to 4 pole MCCB circuit breaker which on th- 100 amp. Now the next step is outgoing supply from the 4 pole MC CB circuit breaker. The N neutral wire will be common for each story or load and you see it in the below diagram, that i connect the neutral black color wire from the breaker and wire it with a connection point connector.

So the neutral will be common for each story or distribution board and one one phase will be distribute to the each story. So i connect the neutral wire to a neutral connection point or connector from where we can get connection of neutral for load.
I connect a neutral wire to this neutral connection point and connect to the story 3 distribution board double pole MCB breaker. And then i get Phase wire from the MCCB and connect to this MCB breaker. Then MCB supply goes to the double pole RCD and you can see it in below diagram. Note these two breaker are 63 amps.

3 phase wiring installation diagram

Now from the RCD breaker the neutral wire goes to neutral connection point as i shown in above 3 phase wiring diagram and the phase (hot wire) red color is goes to all single pole MCB breakers which i shown in above diagram.
In the above3 phase wiring diagram the 2 single pole breaker are 16 amp , 2 are 10 amps and other sex are 6 ampere breaker. Note that this just in example and you must install or wire breaker regarding your total load. Note that use high quality wire for your wiring system. And always chose or use the wire regarding load (amps).

I also wire the voltmeter in above three / 3 phase wiring third story building wiring, for which i get hot wire connection from input points of single pole MCB breakers and neutral from neutral connection connector point. And same i wire the light indicator.
In the above diagram i shown the ammeter connection with current transformer (CT coil) and also provide the complete method of wiring and installation of ammeter with current transformer in above links. However use always the current transformer regarding the ammeter requirements. If the ammeter is 60/5 then use a current transformer with same value 60/5.
You can also use AC series type of ammeter but the CT type ammeter is better then ammeter which we use between supply in series connection.

As i shown in above 3 phase wiring diagram that i do the earthing connection, and provide the earth wire to each point. I shown in bottom of diagram earth symbol with name of earth electrode and from here i provide the ground connection to all story loads / rooms etc. And in each story i use the earth connection point, from where a person can provide the earth wire to any load / electrical machine, outlets etc.

In the above 3 phase wiring diagram 1,2,3,4..... in circle means that these wire goes to load 1 , load 2 and load 3. It's mean that if the 1 hot wire (phase - red) wire goes to the room A then the neutral 1 (black wire) is also for the room A and the earth connection 1 number wire is also for the same point (load- room A).

Follow the same method for story 1 and story 2, but provide the L2 (phase 2 - Hot wire 2 ) to the story 2 and Line 3 to story 1 which is bottom of 3 phase wiring diagram. However lets get another review on diagram step by step.

3 Phase Wiring Step By Step Guide Multi Story Building

  • First of all provide the serves line wire to the 3 phase kWh meter from utility pole.
  • Then provide the 3 phase 4 wire supply to 4 pole MC CB Circuit breaker.
  • Then connect the neutral point from MC CB to neutral connection point.
  • Then get connection from the main neutral point and connect to story 3 or other story double pole MCB circuit breaker.
  • The connect the L1 to the story three double pole MCB between the CT (current transformer) and from MCB connect neutral and phase to the RCD circuit breaker. (Note some people know RCD with name of ELCB  (earth leakage circuit breaker).
  • Then from RCD connect the neutral wire to neutral connection point and phase to circuit single pole breakers.
  • Then provide the supply to the voltmeter and indicator light.
  • Then Do connection between CT coil and ammeter.
  • Then provide the earth connection (green wire) to story three earthing connection point.
  • Then provide the supply to each loads from circuit breaker , neutral connection point and earth / ground connection connectors.
That's all , same follow this method for each story. but provide there own different phase wire and neutral wire.


This in example of 3 phase wiring installation in multi story building, and i use different ampere circuit breaker, just for your understanding. However always use breaker regarding your load. Now i hope you understood the 3 phase wiring in multi story house or building, now if want gave us suggestion or any question then use the below comments section. 


  1. Kindly share with 3 phase selector

    1. Dear I Will publish about three phase selector soon....

      Dear i also share 3 phase voltmeter selector switch wiring diagram and if you did learn about this then kindly read the below post.

  2. Hi, I'm using three phase line. I would like connect ROTARY SWITCH,. Is that possible to connect (4P ISOLATOR- ROTARY SWITCH- 4p MCB). OR By (4P ISOLATOR-4P MCB- ROTARY SWITCH). COULD YOU explain 4p ISOLATOR- ROTARY SWITCH - 4mcb CONNECTION with diagram.

  3. Great post, and great website. Thanks for the information! Auto Electrician Werribee