Three Phase Electrical Wiring Installation in Home – NEC & IEC
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 generated power 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:
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.
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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.
Following are the Voltage levels available in the USA and Canada.
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
i.e.
- Between L1, L2 & L3 = 208V, 240V, 480V or 600V – (3-Phase)
1-Phase Voltage in the USA
- Hot to Neutral = 120V – 1-Φ
- Hot to Neutral = 208V, (High Leg Delta) – 1-Φ
- Two Hot = 240V – 1-Φ (Split Phase)
- Hot to Neutral – Wye = 277V – 1-Φ
- 2 Hots + Neutral – Wye = 480V – 1-Φ
- Hot + Neutral – Wye = 347V – 1-Φ
i.e.
-
- L1 to N = 120V, 208V, 277V, 347V, 480V or 600V – (1-Phase)
- L2 to N = 120V, 208V, 277V, 347V, 480V or 600V – (1-Phase)
- L3 to N = 120V, 208V, 277V, 347V, 480V or 600V – (1-Phase)
Note: In case of High Leg Delta (Power Leg or Wild Leg), additional of 208V single phase voltage are available between High Leg & Neutral as well as 120V, & 240V are available from the meter box to the load center and panel box.
Related Wiring Tutorials:
- How to Wire 1-Phase Split Load Consumer Unit? – RCD+RCBO
- How to Wire 230V Dual Split Load Consumer Unit? – RCD+MCB
Three Phase and Single Phase Supply Voltage Systems “120V, 208V, 240V, 277V & 480V” – NEC – US
High Leg Delta Configurations (120V, 208V & 240V)
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.
3-Phase Voltage in the UK & EU
- Phase to Phase = 400V
- Any Phase to Neutral = 230V – (1-Φ)
- Between Three Phases = 400V – (3-Φ)
I.e.
- L1 to L2 = 400 V – (3-Phase)
- L2 to L3 = 400 V – (3-Phase)
- L3 to L1 = 400 V – (3-Phase)
1-Phase Voltage in the UK & EU
- Phase to Neutral = 230V
i.e.
- L1 to N = 230 V – (1-Phase)
- L2 to N = 230 V – (1-Phase)
- L3 to N = 230 V – (1-Phase)
230V & 400V Single Phase & Three Phase Power Supply Systems – IEC – UK & EU
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Requirements for Three Phase Wiring Installation
In this tutorial, we need the following wiring accessories to wire three phase power in home.
- Three Phase Energy meter: 1 No
- Three Pole MCCB, 63A (100 or 250A in US) : 1 No
- Double Pole: 63A, 30mA Trip Current (RCD/GFCI): 3 No
- Triple Pole MCBs, 63A (100-250A In US): 3 Nos
- Single Pole, 20A, MCB: 6 Nos
- Single Pole, 16A (20A in US): MCB: 3 Nos
- Single Pole, 10A (15A in US): MCB: 6 Nos
- Distribution board cases: 3 Nos
- Bus bar Link for Neutral Cable Connections
- Copper strips for MCB common connection: 3 Nos (Cu Busbar segment)
- Copper strip Busbar for Earth & Ground Link
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 from 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 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.
In addition, If you need to connect a single phase load or need to wire a separate consumer unit or subservice panel, read the previous published posts on single phase wiring diagrams.
Related Posts:
Below are given the Three Phase Distribution Electrical Wiring Installation Diagram according to NEC & IEC.
Three Phase Electrical Wiring Installation Diagrams – US -NEC
Three Phase 208V Distribution and Panel Wiring.
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Three Phase 240V (High Leg Delta) Distribution and Panel Wiring.
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Three Phase 480V Distribution and Panel Wiring.
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Related Posts:
- How to Wire Single-Phase, 230V Consumer Unit with RCD? IEC, UK & EU
- How to Wire 1-Phase & 3-Phase Split Load Distribution Board?
- How to Wire Automatic UPS / Inverter to the Home Supply System?
Three Phase Electrical Wiring Installation Diagrams – UK, EU – IEC
Click image to enlarge
Note: The same description and details can be used for both NEC and IEC wiring diagrams as mentioned for the above general fig 1.
Three Phase, 400V, Split Distribution Board Wiring with RCD – Only 3-Φ Loads
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Three Phase, 400V, Split Distribution Board Wiring with RCD – 1-Φ Loads from 3-Φ Supply
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Three Phase, 400V, Split Distribution Board Wiring with RCD – Combo of 3-Φ & 1-Φ Loads
Click Image to enlarge
Three Phase, 400V, Typical Distribution Board Wiring with RCD for 3-Φ Load Circuits
Click image to enlarge
Three Phase, 400V, Typical Distribution Board Wiring with RCD for Both 3-Φ & 1-Φ Load Circuits
Click image to enlarge
Related Posts:
How to Connect Single Phase 120V Loads in a 1-Phase Wiring Distribution System? – NEC – US
Three phase load circuits can be directly connected to the three hot wires. Keep in mind that Neutral is not needed in all cases. The single phase load can be connected to hot and neutral (120V) or two hot wires (240V single phase). Below are the typical three phase panel wiring for US and Canada.
Wiring Installation of Three Phase, 208V Circuits & Breakers in Main Service Panel.
Wiring Installation of Three Phase 240V (High Leg Delta) Circuits & Breakers in Main Service Panel.
Wiring Installation of Three Phase 480V Circuits & Breakers in Main Service Panel.
Related Posts:
How to Connect Three Phase, 400V Loads in a 3-Phase Wiring Distribution System? – IEC & UK
As mentioned above, Three Phase loads (400V, 3-Phase Motors) can be directly connected to the three lines accordingly i.e. there is no need to connect to the neutral point (In some cases, Neutral is still needed in a three phase system which depends on the system design. Refer to the user manual before installing such an appliance). For Single Phase Loads (230V or 120V AC Light, TV, Power socket, Fans etc.), they can be connected to the Phase and Neutral wire as shown below. Note that Earth or ground wire must be connected to the electrical appliances and equipment connected to both single phase and three phase supply systems for safety as it prevents electric shock hazards.
Wiring 3-Phase, 400V Load Points and MCB with RCD & RCCB in Distribution Board
Wiring Three Phase 400V load and MCB’s in the Split Load Distribution board and consumer unit with RCD.
Wiring Typical Three Phase 400V load circuits and MCB in the Distribution board and consumer unit.
Related Posts:
- Staircase Wiring Circuit Diagram – How to Control a Lamp from 2 Places?
- Corridor Wiring Circuit Diagram – Hallway Wiring using 2-Way Switches
Schematic Wiring Diagram of Three Phase Distribution Board
The following typical layout wiring diagram shows three phase distribution board and consumer unit installation in a residential/commercial area.
Three Phase Wiring Color Codes – IEC and NEC
NEC – USA: Three Phase 208V & 240V AC (High Leg Delta): Three Phase 277V & 480V AC: Single Phase 120V AC: Single Phase 240V AC: Related Posts: IEC & UK: Three Phase 400V: Single Phase 230V AC: 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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General Precautions & Instructions
You may also check the related Electrical Wiring Installation Tutorials.
- Staircase Wiring Circuit Diagram – How to Control a Lamp from 2 Places?
- Corridor Wiring Circuit Diagram – Hallway Wiring using 2-Way Switches
- Tunnel Wiring Circuit Diagram for Light Control using Switches
- Hospital Wiring Circuit for Light Control using Switches
- Hotel Wiring Circuit – Bell Indicator Circuit for Hotelling
- Hostel Wiring Circuit Diagram and Working
- Godown Wiring Diagram – Tunnel Wiring Circuit and Working
- How to Wire 120V Water Heater Thermostat – Non-Simultaneous?
- How to Wire a Pilot Light Switch? Wiring of 2 & 3 Way Neon Light Switches
- How to Connect a Portable Generator to the Home Supply – 4 Methods
- Even More Electrical Wiring Installation & Tutorials
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In the diagram, no protection (switchgear) is used between utility pole and incoming of 3-ph energy meter…is direct connection from utility pole to meter OK or is it necessary to use any fuse/cut??
Thanks. The information is very useful since I am constructing my own 4 bedroom house in New Delhi. I have a query though: i would like to have one light; fan and TV in each room to be connected to a single phase UPS. The electrical contractor is asking for high extra payment for doing this. Would there be significant extra cost involved. I would have thought that the only extra is drawing one wire from the mains to the UPS and from the ups to the bus for emergency circuits. The wiring of the mergency circuits would not change since they would get power from the grid normally and from the ups in case of power failure
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One ups power and multi utility meters wiring diagrams
I want to 3,phase and single phase electrical panel energy meter CIRCUIT
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Please can you guide or send me a link to understand a change over switch and a phase selector in a 3 phase environment.
Consider a max 10 KW connection is provided by electricity board then what will be max power capacity at each phase?
Total Power : 10 KW
Electricity Board : MAHA VITARAN
Phase 1(R) : V = ? & I = ?
Phase 2(Y) : V = ? & I = ?
Phase 3(B) : V = ? & I = ?
we ask some question the building the install wiring is three phase but the wiring is single phase that building have a laboratory so i think some lab need 3 phase for the units so how to install 3 phase electrical wiring , the electric compony install 25 kva its that enough for the load of the building.
I can not understand how Phase to Phase voltage is 440 volt , and phase to neutral voltage is 230 v ?
as i know V phase to neutral = VLine/ root 3
so for 440v VL , V phase = 254 volt ?
please correct if I am wrong
You are ignoring the Power factor in 3 Phase system….
25hp motor can you use 220v contactor?
yes of course . you can use . but the conducting capicity should be higher than your running load .
Easy to follow description for Electrical Professionals and even other engineering fields.
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how should i wire a three phase water heater to single phase 240 volt. i have two 120 legs and a neutral to attach to 3 lugs and a neutral in the heater.
Please can you present a well illustrated diagram showing how a free standing 3-Phase AC is connected. I am intrested in the details at the switching point of the AC.
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mandepartners
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Please give me a practical example on how to determine the DB load balancing for a three phase supply system for an architectural building design electrical drawing aspect.