How to Wire 3-Phase Electrical Distribution Board & Consumer Unit in Home
In our today electrical wiring installation tutorial, we will show how to wire and install a Three Phase distribution board and Consumer Unit from utility pole to a 3-Phase Energy Meter & 3-Phase Distribution board. We will also be showing that How to connect Three Phase & Single Phase Load circuits in a Three Phase Wiring Distribution System in home and commercial electric supply system.
Related Wiring Tutorials:
3-Phase Electrical Distribution Wiring Installation in Multistory Building
Single Phase Electrical Wiring Installation in Home – NEC & IEC
Single-Phase Electrical Wiring installation in a Multi-Story Building
What is Three Phase & Single Phase Power?
In power generation plants, Three Phase power is generated by an electrical generator or alternator. In an alternator, the generated voltage and current by three independent coils in the stator are separated by 120 degrees from each other. The power generated from alternators then transmitted and distributed through transmission and distribution lines to the sub distribution. Both single phase and three phase supply is further distributed by the three single phase transformers or a single unit of three phase transformer (configured in Star “Y” or Delta Connection) installed on the utility pole near the residential or commercial area.
The voltage levels are step-up via step-up transformers for power transmission. In the distribution system, they are again step-down the level of voltage via step-down transformer for further utilization. RCD, MCB, MCCB, CB, RCD, RCBO, Fuses, Switches etc are used as controlling and protective devices in the MDB, DB, Sun & Final Sub circuits. For example,
In the UK and EU, 11kV from the step-down transformer wired in Delta connection via (3 Phase, 3-Wires System) enters the 400V/230V distribution transformer wired in Star “Y” Connection (Three Phase, 4 Wires System).
In the US, 4.5k-7.2kV from the step-down transformer wired in Delta connection via 3 Phase, 3-Wires System enters the 240V/120V distribution transformer wired in Star Connection (Two Phase, 3 Wires System). For a three phase system, the arrangement can be different for different levels of voltage. We will show the wiring diagram in the next sections of this post.
Related Wiring Tutorials:
How to Wire Combo of 3 & 1-Φ, 400V/230V Distribution Board?
How to Wire a Three Phase, 400V Distribution Board? IEC & UK
As high power is needed in industrial and commercial buildings, they are connected to the three phase Delta connection (3 Phase – 3 Wire System – No Neutral Wire) before distribution transformer and then manage the required voltage and current according to the system requirements in three phase and single phase supply.
On the other hand, buildings that need low as well as high power in three phase and single phase are connected to the secondary of the distribution transformer. This way, they get a three phase Star connection (3-Phase, 4 Wire System with Neutral Wire). In the Star connection, Three Phase Line to Line (Phase to Phase) voltages are 400V AC (in US, 208V, 240V, 480V etc) and Single Phase Line to Neutral (Phase to Neutral), there are 230V AC (120V, 208V , 240V, 277V, 480V etc in the US).
In Three Phase Supply, motors and large electric heaters can be directly connected to the three Phases (Neutral is not needed in all cases) while in Single Phase, load circuits (light, fan etc.) can be connected in between Phase and Neutral through proper protective devices e.g. earthing/grounding wire. In the US, the 240V Single phase load can be connected to two phases without a Neutral wire.
Why Do We Need Three Phase Power Supply?
To operate high power equipment and appliances such as electric motors, high power rated air compressors & air-conditions, water heaters etc. we need Three Phase Power supply instead of Single Phase Power supply. In ordinary homes (domestic as residential), we mostly use Single Phase power supply to operate lighting load, fans, washing machines etc. But in some cases e.g. Industries, high torque motors, multi-story & large buildings (industrial as commercial), Three Phase power supply needed to operate and maintain the high power and voltage systems.
In our previous posts about Single Phase electrical wiring installation in home and already know what MDB, DB, Final Sub Circuit, MCB, MCCB, CB and RCD etc. So we will never repeat it again.
3-Phase & 1-Phase Voltage Levels in the US – NEC
In United States and Canada, different single phase and three phase voltage levels are available i.e. Single phase voltage is available for domestic and residential applications while three phase voltage can be used for industrial and commercial applications.
3-Phase voltage in the USA
Three Hots (3-Lines) = 208V- 3-Φ
Three Hots (3-Lines) – High Leg Delta = 240V– 3-Φ
Three Hots (3-Lines) – Delta = 480V- 3-Φ
Three Hots (3-Lines) – Wye = 600V- 3-Φ
3-Phase & 1-Phase Voltage Levels in the UK, EU – IEC
The three phase system is simpler in the UK & EU as compared to the USA and most of the countries (e.g. India, Pakistan, UAE and other Arab countries) follow the same voltage distribution system as UK, EU and IEC voltage levels. Both three phase and single phase voltage are available for residential and commercial application in the same unit as follows.
How to Wire Three Phase Main Distribution Board?
Generally, Electric supply and service providers install a single phase energy meter when load is less than 7.5kW (10HP) in domestic areas (consumer unit for home). If the limit is exceeded, then it’s recommended to install a 3-phase energy meter for consumer units. When load exceeds 7.5 kW, then 3-phase electrical wiring is recommended in domestic areas (homes).
In this tutorial, we assume that we will only connect single phase load (Light points, fans, TV, Power Socket, AC etc.) in the current section of three phase electrical wiring installation. In other words, we will not power up 3 phase motors because in our homes, we don’t have that kind of (three phase) loads. If a three phase load exists in your home, then you can do so. As we can see that the total load is exceeded the limit of single phase electrical wiring installation as we will be feeding different rooms and areas in the home, that’s why we have to wire our distribution in three phase system. For direct three phase loads, see the next sections in this post.
Practical Procedure of Three Phase wiring of distribution board & installation
We have learned the basic electrical wiring of bulb, fans etc (i.e. Sub-circuits and final sub circuits) in our previous posts, so follow the steps below to do the same as mentioned below.
First of all, connect the three-phase energy meter as shown in fig. (If you don’t sure how to wire a 3-phase energy meter, then check this simple tutorial which shows How to wire a Three-Phase Energy Meter.
Connect the MCCB (Molded Case Circuit Breaker) as main switch to the incoming three phases (R, Y, B) from 3-phase energy meter. (Check the wiring color code for different areas in below section)
Now connect the outgoing three phases (R, Y, B) from MCCB (Molded Case Circuit Breaker) to the DP (Double Pole MCB, RCD, SP (Single Pole MCBs and load) as shown in fig)
Now connect the RCD from DP with Phase (Line) and Related Neutral Link. The Outgoing Phase lines should be connected to the final and final sub circuits. The same can be done for Neutral Wires.
Finally, Connect the electrical appliances with the Earth link terminal which leads to the earth electrode in the earthing and grounding system as shown in fig below.
Follow the same steps for all three distribution boards for different rooms and areas.
How to Wire 3-Phase Electrical Distribution Board & Consumer Unit in Home
In our today electrical wiring installation tutorial, we will show how to wire and install a Three Phase distribution board and Consumer Unit from utility pole to a 3-Phase Energy Meter & 3-Phase Distribution board. We will also be showing that How to connect Three Phase & Single Phase Load circuits in a Three Phase Wiring Distribution System in home and commercial electric supply system.
Related Wiring Tutorials:
3-Phase Electrical Distribution Wiring Installation in Multistory Building
Single Phase Electrical Wiring Installation in Home – NEC & IEC
Single-Phase Electrical Wiring installation in a Multi-Story Building
What is Three Phase & Single Phase Power?
In power generation plants, Three Phase power is generated by an electrical generator or alternator. In an alternator, the generated voltage and current by three independent coils in the stator are separated by 120 degrees from each other. The power generated from alternators then transmitted and distributed through transmission and distribution lines to the sub distribution. Both single phase and three phase supply is further distributed by the three single phase transformers or a single unit of three phase transformer (configured in Star “Y” or Delta Connection) installed on the utility pole near the residential or commercial area.
The voltage levels are step-up via step-up transformers for power transmission. In the distribution system, they are again step-down the level of voltage via step-down transformer for further utilization. RCD, MCB, MCCB, CB, RCD, RCBO, Fuses, Switches etc are used as controlling and protective devices in the MDB, DB, Sun & Final Sub circuits. For example,
In the UK and EU, 11kV from the step-down transformer wired in Delta connection via (3 Phase, 3-Wires System) enters the 400V/230V distribution transformer wired in Star “Y” Connection (Three Phase, 4 Wires System).
In the US, 4.5k-7.2kV from the step-down transformer wired in Delta connection via 3 Phase, 3-Wires System enters the 240V/120V distribution transformer wired in Star Connection (Two Phase, 3 Wires System). For a three phase system, the arrangement can be different for different levels of voltage. We will show the wiring diagram in the next sections of this post.
Related Wiring Tutorials:
How to Wire Combo of 3 & 1-Φ, 400V/230V Distribution Board?
How to Wire a Three Phase, 400V Distribution Board? IEC & UK
As high power is needed in industrial and commercial buildings, they are connected to the three phase Delta connection (3 Phase – 3 Wire System – No Neutral Wire) before distribution transformer and then manage the required voltage and current according to the system requirements in three phase and single phase supply.
On the other hand, buildings that need low as well as high power in three phase and single phase are connected to the secondary of the distribution transformer. This way, they get a three phase Star connection (3-Phase, 4 Wire System with Neutral Wire). In the Star connection, Three Phase Line to Line (Phase to Phase) voltages are 400V AC (in US, 208V, 240V, 480V etc) and Single Phase Line to Neutral (Phase to Neutral), there are 230V AC (120V, 208V , 240V, 277V, 480V etc in the US).
In Three Phase Supply, motors and large electric heaters can be directly connected to the three Phases (Neutral is not needed in all cases) while in Single Phase, load circuits (light, fan etc.) can be connected in between Phase and Neutral through proper protective devices e.g. earthing/grounding wire. In the US, the 240V Single phase load can be connected to two phases without a Neutral wire.
Why Do We Need Three Phase Power Supply?
To operate high power equipment and appliances such as electric motors, high power rated air compressors & air-conditions, water heaters etc. we need Three Phase Power supply instead of Single Phase Power supply. In ordinary homes (domestic as residential), we mostly use Single Phase power supply to operate lighting load, fans, washing machines etc. But in some cases e.g. Industries, high torque motors, multi-story & large buildings (industrial as commercial), Three Phase power supply needed to operate and maintain the high power and voltage systems.
In our previous posts about Single Phase electrical wiring installation in home and already know what MDB, DB, Final Sub Circuit, MCB, MCCB, CB and RCD etc. So we will never repeat it again.
3-Phase & 1-Phase Voltage Levels in the US – NEC
In United States and Canada, different single phase and three phase voltage levels are available i.e. Single phase voltage is available for domestic and residential applications while three phase voltage can be used for industrial and commercial applications.
3-Phase voltage in the USA
Three Hots (3-Lines) = 208V- 3-Φ
Three Hots (3-Lines) – High Leg Delta = 240V– 3-Φ
Three Hots (3-Lines) – Delta = 480V- 3-Φ
Three Hots (3-Lines) – Wye = 600V- 3-Φ
3-Phase & 1-Phase Voltage Levels in the UK, EU – IEC
The three phase system is simpler in the UK & EU as compared to the USA and most of the countries (e.g. India, Pakistan, UAE and other Arab countries) follow the same voltage distribution system as UK, EU and IEC voltage levels. Both three phase and single phase voltage are available for residential and commercial application in the same unit as follows.
How to Wire Three Phase Main Distribution Board?
Generally, Electric supply and service providers install a single phase energy meter when load is less than 7.5kW (10HP) in domestic areas (consumer unit for home). If the limit is exceeded, then it’s recommended to install a 3-phase energy meter for consumer units. When load exceeds 7.5 kW, then 3-phase electrical wiring is recommended in domestic areas (homes).
In this tutorial, we assume that we will only connect single phase load (Light points, fans, TV, Power Socket, AC etc.) in the current section of three phase electrical wiring installation. In other words, we will not power up 3 phase motors because in our homes, we don’t have that kind of (three phase) loads. If a three phase load exists in your home, then you can do so. As we can see that the total load is exceeded the limit of single phase electrical wiring installation as we will be feeding different rooms and areas in the home, that’s why we have to wire our distribution in three phase system. For direct three phase loads, see the next sections in this post.
Practical Procedure of Three Phase wiring of distribution board & installation
We have learned the basic electrical wiring of bulb, fans etc (i.e. Sub-circuits and final sub circuits) in our previous posts, so follow the steps below to do the same as mentioned below.
First of all, connect the three-phase energy meter as shown in fig. (If you don’t sure how to wire a 3-phase energy meter, then check this simple tutorial which shows How to wire a Three-Phase Energy Meter.
Connect the MCCB (Molded Case Circuit Breaker) as main switch to the incoming three phases (R, Y, B) from 3-phase energy meter. (Check the wiring color code for different areas in below section)
Now connect the outgoing three phases (R, Y, B) from MCCB (Molded Case Circuit Breaker) to the DP (Double Pole MCB, RCD, SP (Single Pole MCBs and load) as shown in fig)
Now connect the RCD from DP with Phase (Line) and Related Neutral Link. The Outgoing Phase lines should be connected to the final and final sub circuits. The same can be done for Neutral Wires.
Finally, Connect the electrical appliances with the Earth link terminal which leads to the earth electrode in the earthing and grounding system as shown in fig below.
Follow the same steps for all three distribution boards for different rooms and areas.
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