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How To Wire a Single Phase kWh Meter? 120V/240V & 230V AC – NEC & IEC

Installation of 1-Phase Energy Meter | 1-Φ, 2-Wires Electric Meter for 230V & 120V/240V AC Mains Supply & Service

(From the Power Supply to The Main Distribution Board (MDB) & Load Centers according to NEC & IEC)

In the following step by step meter installation guides, we will show how to wire a single phase electric meter for 230V AC (UK, EU based on IEC) and installation of single-phase 120V and 240V (US based on NEC) regulations for existing or new mains service installation.

For general and clear illustrations, we have used the RED color for Phase, Line or Live wire while the BLACK color shows the Neutral wire. The color coded versions are also included for both IEC and NEC wiring color coeds.

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How To Install a 1-Phase kWh Meter for 230V, 120V & 240V - IEC & NEC

Warning: These examples show the most commonly used arrangement and generic wiring for electric meter installation in the UK, EU, India, Pakistan, South Africa, United Arab Emirate and other IEC (International Electrotechnical Commission) following countries. The same rule applies for NEC (National Electrical Codes) in the US and Canada. There may be some variations depending on the specific areas, meter designs (smart electronics or electromechanical) and supply systems. The setting may be different in other types of kWh or electric energy meters in different locations around the world. For proper safety. Please contact the supply and service provider to confirm the connection type before electrical wiring installation.

Keep in mind doing your own electrical work is dangerous as well as illegal in some cases. Contact the licensed electrician or the electric power supply provider before practicing any change/modification in electrical wiring connections. In addition, It is must to obtain necessary licenses and approval from the local authority before doing the existing or new service installation.

Be careful: Do not contact metal tools to the screw terminals if the circuit is live especially in case of 230V & 400V Meters (IEC) as the terminal block screws are not insulated. 

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 the wrong format. So please! Be careful because it’s all about electricity and electricity is too dangerous.

Single Phase Meter Wiring for 230V AC – (UK & EU) – IEC

In UK, EU, Asia and IEC following countries, the single phase supply of 230V AC is provided by two wires systems (Phase & Neutral) from the transformer (Single-Phase 230V, or Three Phase 400/230V Transformer) to the meter box and further to the main distribution board in the residential premises.

An electric meter (aka energy meter or kWh meter “kilo-watt-hour”) can be digital (smart with an LED display known as electronic meter) or analog (electromechanical) having a rotating aluminum disk. Nowadays, smart electric meters are commonly used due to extra useful features and advantages over the old school technology, That’s why the Govt of UK required electric energy suppliers to install smart meters instead of analog meters.

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IEC Wiring & Connection Diagram for 1-Φ, 2-Wires, 230V AC Meter

Installation of Single Phase kWh Meter (1-Phase, 2 Wires, 230V AC Energy Meter)

  1. First of all, make sure to disconnect the main power before working on electrical installations.
  2. Starting from the left side for MAIN, connect the incoming (from transformer) Phase (Line) wire to to the 1st slot on the meter (Main).
  3. Connect the incoming Neutral (N) wire to to the 2nd slot on the meter.
  4. On the Load side, connect the Outgoing Neutral in the 3rd slot.
  5. Now connect the outgoing Phase wire in the 4th slot and connect it to the main distribution board as shown in the fig.

Below is the basic connection diagram for installation of a Single-Phase2-Wires) kWh meter (Digital or Analog Energy Meter) from the 230V AC supply to the main distribution board in home.

Click image to enlarge

How to Wire a 230V, 1-Phase Electric Energy Meter

Make sure the position of meter should be vertical on its center line. Securely tight the bolts, washers and nuts etc and after connecting the wires to the meter, Close the safety windows. This way, the installation work of single phase meter box is successfully completed. You may turn ON the main power to check and verify if everything is fine and working accordingly.

Here is another live example of an energy meter which has been installed on the main pole (utility pole) near to the consumer buildings.

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Wiring a Single-Phase Digital or analog Energy Meter from the Supply to The Main Distribution Board for 230V AC

In the above figures and diagrams:

  • PIN =  Incoming Phase or Live from the source of supply voltage (i.e. from transformer)
  • POUT = Outgoing Phase or Line to the home main distribution board.
  • NIN =  Incoming Neutral from the source of supply voltage.
  • NUOT = Out going Neutral to the home main distribution board.

General Requirement for 230V, 1-Phase Meter Installation

  • You must contact and inform the electricity providers before any kind of service installation/modification or wiring a meter.
  • Only use single core PVC, double insulated for all cables.
  • 900mm clearance space in width should be provided in case of electric meters and Low voltage panels and switchgears with a rating of +100 Amps.
  • Use minimum of 4mm2 (stranded copper wire) between the consumer unit and electric meter.
  • The meter tails (cables used to connect your meter to the cut out o or main breaker) should be double insulated in size of 25mm and properly terminated in to the meter slots.
  • The meter tails should be the shortest possible, or at least, the length of meter tails from the cut-out through the metering equipment to the consumer unit) should always be no more than 3 meters of cable (more on BS7671 Reg. 434.2.1).  
  • You will have to contact a licensed electrician to connect wires from the distribution board to the electric meter. The electricity will be provided later by power service providers by showing them the BS7671 certificate signed by your electrician.
  • The meter box must be installed on the external side of the wall which can be easily accessible from the front and unlikely to be damaged.
  • There should not be a gas meter, telephone and other utility equipment above or below the electric meter box.
  • The meter cabinet (surface mounted or flush mounted) approved by UK power networks can be used based on the proper guidelines and codes.

An 38 mm hockey stick (performed tube) with the meter cabinet must be installed according to the following minimum specifications.

Meter cabinet from the ground level

  • 600 mm Min
  • 1100 mm Max

Meter tails

  • 25mm

Clearance from front of cabinet

  • Min 1000 mm

Hockey stick (preformed tube)

38 mm ( min 1450mm high &  310mm long) and 500 mm minimum depth in garden.

Cable access hole

  • 20/30 mm

The overall single phase meter wiring (IEC color coded) from the utility power supply to the main distribution board will look like this.

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How to Wire a Single Phase Consumer Unit with RCD - IEC, UK & EU

Single phase meter wiring using the old UK color coded version (prior to 2004) but still appliable to other counties in the Asia & KSA, UAE, SA etc.

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How to wire RCD (Residual Current Device) - Wiring of the Distribution Board with RCD (Single Phase Home Supply From Utility Pole & Energy Meter to the Consumer Unit)
How to wire RCD (Residual Current Device)?

Single-Phase Meter Wiring for 120V & 240V – US – NEC

The level of voltages are different for both single phase and three phase supply in the US as compared to the UK and EU. This way, the equipment designs for devices and meters are also different for multiple voltage levels. For example, In case of utility pole mounted single phase transformer (7200V/240V & 120V) the level of voltage between a Line and Neutral wire is 120V single phase (2 Wires as Hot & Neutral), while the voltage between two Hot wires (Hot 1 & Hot 2) is 240V single phase.

In the following sections, we will show how to wire an electric meter for 120V and 240V single phase according to NEC.

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Lugs (Jaws) & Prongs on 240V-120V Electric Meter & Socket

How to Wire 120V Single-Phase Electric Meter?

Let’s see how to wire a 1-phase, 2 wires, 120V AC energy meter.

  1. First of all, make sure to disconnect the main power supply before working on electrical installations.
  2. Connect the Line IN incoming from the transformer as “HOT” wire to the top left lug (Black Color).
  3. Connect Line OUT as “HOT” wire (to the load side) from the top right lug to the load center or panel box main breaker (Red Color).
  4. Connect a jumper wire (White Color) between the two lower lugs as shown in fig.
  5. You may connect the neutral to the center lug labeled as (G & N) but it is optional. Just connect the load side Line (Hot) and Neutral wires to the main breaker box. The wire strip on the back side of the DEM meter to the neural point should be connected according to manual (see following notes for it). Keep in mind that this latch only comes with meter for 120V or both 240V & 120V split phase supply but not with the meters designed only for 240V.
  6. You may use #10AWG (Copper) or #8 AWG (Aluminum) for these 120V circuits (see details below).
  7. #4 AWG (American Wire Gauge) copper wire is suggested for the ground (protective earth) connection.
  8. Now carefully install and fix the meter without pinching flexible wire in the meter box (i.e. 4 meter prongs to 4 jaws in the meter box).

Click image to enlarge

In the case of DEM type meters, remove the clip on the back side of the meter. If the Neutral wire (White Color) is connected to the central lug in the meter socket, just connect the flexible wire (18-20 AWG) on the screw of back side of meter to that Neutral terminal, if not, just connect to other neutral points such as Neutral bar in the panel box. Keep in mind that there is no need to connect the neutral to the meter socket in case of USG meter kits.

The latch or metal tape must be closed to record and read kWh meter for electric bill calculations and watt hour usage. Also note that the wrong connection of this flexible wire to other screws will trip the breaker, may cause a flash, damage to the meter or even serious injury with hazardous fire.

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Back Side of the 120V & 240V Meter for Latch & Strip Wiring to the Neutral-Ground Point

How to Wire 240V Single-Phase Electric Meter?

Let’s see how to wire a 1-phase, 3 wires or 2 wires, 240V & 120V AC electricity meter.

  1. Disconnect the main power supply before working on electrical installations.
  2. Connect the incoming Line 1 IN (as Hot 1) wire from the transformer to the top left lug (Red Color).
  3. Connect the incoming Line 2 IN (as Hot 2) wire from the transformer to the top right lug (Black Color).
  4. Connect Line 1 OUT wire as “HOT 1” (to the load side) from the bottom left lug to the load center or panel box main breaker (Red Color).
  5. Connect Line 2 OUT wire as “HOT 2” (to the load side) from the bottom right lug to the load center or panel box main breaker (Black Color).
  6. Optionally, You may connect the neutral wire to the center lug labels as N & G. As there is no need for Neutral if you run only 240V circuits. If you still need 120V circuits, you will have to wire the Neutral wire to the panel box where 120V AC is available between any Hot wire and a neutral wire, whereas 240V single phase is available between two hot wires.
  7. You may use #8AWG (Copper) or #6 AWG (Aluminum) for 240V circuits (see details below).
  8. #4 AWG copper wire is suggested for the ground (protective earth) connection.
  9. Now carefully stab the meter in the meter socket (with a strong push) and restore the power to verify everything is well and working properly according to the plan and design. Done.

Click image to enlarge

How to Wire Single-Phase 240V & 120V kWh Meter

Cable & Wire Sizes For Hot, Neutral & Ground – NEC

Use a proper wire size based on the load circuits. In this general scenario, you may use #10AWG (Copper) or #8 AWG (Aluminum) for these 120V circuits. For 100 Amps, you may use #4 AWG for Copper and #2 AWG Aluminum for service lines (both Hot and Neutral). Similarly, For 100 Amps, you may use 2/0 kcmil (AWG) for Copper and 4/0 kcmil for aluminum (based on NEC table 250.122). In addition, it is required to use a minimum of #4 AWG wire for ground wire to the grounding rod. You may check with local area code for confirmation.

The following table shows the typical wire sizes of Miniman Line conductor, Neutral conductor and Ground wire. 

Breaker size Typical Wire Sizes For Meter & Panel Box
Line Conductor Neutral Conductor* Ground wire
Aluminum Copper Aluminum Copper Aluminum Copper
100 Amp #2 #4 #4 #4 #6 #4
200 Amp 4/0 2/0 2/0 1/0 #2 #4

*Neutral size is determined by load calculation and NEC table 250.122. Always check with your local area codes.

Here is the table in image format if you need to downland as a reference.

Wire sizes of Line Neutral and Ground wire for Meter and Breaker Size - NEC table 250.122

General Requirement for 120V, & 240V, 1-Phase Meter Installation

  • The meter box must be tightly and securely attached to the wall or firmly fixed to a solid surface at the right level.
  • Only use the approved material for the meter box such as conduit and galvanized pipe and attachment brace.
  • The wires and lugs connecting screws must be tightened i.e. strong termination.
  • Use proper wire size for the exact ampere rating of equipment as well as the amps capacity of panel box and load centers.
  • Check the latch on the back side of the meter for proper connection according to 120V and 240V meters.
  • Finally, check and verify the wiring connection according to the user manual guide provided by the supplier with the meter.

Meter box from the ground level

  • 4ft to 5′-6″.

Clearance from front of meter box cabinet

  • Min 4ft clear space & 12 inch on all sides.

Separation with Gas & other meters

  • Minimum 3 to 5ft & 6 inches on the outlet side of gas meter bar.

Underground pipe connection

  • Minimum 18 Inches below the ground line.

Rigid Conduit

  • As per NEC

Grounding Wire Size to the Ground Rod

  • #4 AWG (Copper)

Related Wiring Tutorials about NEC and IEC:

Load Center, Panel & Distribution Boards Wiring Tutorials

NEC – USA

IEC – UK & EU

General Home Wiring (Both NEC & IEC)

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11 Comments

  1. Anonymous says:

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  2. Thilak raj says:

    thanks for the great info.<br />i need another info like this.<br />i.e i have a single 3 pin plugin socket connector and i have energy meter like as you shown above so how to connect the 3 pin spike buster plug to energy meter to find out energy consumed?

  3. Nabeel Taj says:

    please tel me that the neutral of input and output are common or not in digital energy meter

  4. I read this paragraph fully about the difference of
    most recent and preceding technologies, it’s remarkable article.

  5. Muhammad Hayat says:

    GoodGood knowledge

  6. abdullateef moshood says:

    Good good one

  7. Doulathrao Kadam says:

    what happen when two meters r connected in parallel. Whether the consumption of units of both meters r same or differ.

    1. Dear Sir,
      We have already done the experiment by connecting two parallel wires to two different energy meters, connected (common single load of) halogen lamps of 2 X 1 Kw, capacity each, both the lamps connected parallel, and each input and output connected to 2 X 42.5 Mtr. wire length to each lamp.

      Wire resistance was 1.032 and other 4 wires of 1.63, 1.9, 2.03, 2.33 and 2.37 connected simultaneously against common wire having 1.03 Ohm. each length was 42.5 X 2 mtr length.

      Live source to both the meter, and neutral to 2 nd meter, Neutral made common at mtr end to run both the energy meter.

      Current observed 8.69 Amps = I1 + I2 , 230 V for both lamps at source. It was observed that 2 nd mter reading was moving fast, and the ratio of power consumption observed in the ratio of 1.6/1.032 ohms. Calculated Amps for each lamps 4.35 amp.

      Power consumption in second meter observed fast compared to 1st, even after alter terminations from 2 nd to 1 st meter.

      Result are attached. This is because of high resistance in wire. as per calculation losses is comes approxy.

      KWH ( Power in Hour) = KW ( Speed) X Hours, Hence in less ampacity wire takes more time to consume same enegy, and it is proportional to its resistance ratio.

      We can say if the ampacity of wire does not meet the requirement in high res. wires takes more time and leading to heat the wire also.

      If same wire connected to AC , high res wire takes more time to cool the room compared to low res wire.

      waiting response from expert, energy saving point of view.

      M. No 7718885109.

  8. Venkatesh R Kamat says:

    How to find out meter is running or electricity is consuming in digital meter. Earlier we had mechanical ring rotating that was evident. Now not able to find out.

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