EIS 004: Battery Installation – Neutral continuity and MEN Connection

Overview - June 2023

Energy Safe Victoria has been made aware of an electric shock incident that potentially related to the installation of a battery system at a residential installation that provided backup power in the event of a grid outage.

Hazards

Energy Safe's investigation into the matter identified 2 separate non-compliances creating hazards in battery system installations:

1. The battery system was installed without continuity between the main neutral bar and the back up circuit neutrals, negating a fault return path.
2. The property had a Main Earth Neutral (MEN) connection at the main neutral bar as required, but there was a second MEN created at the battery system stand-alone output port neutral connection.

A number of other installations have been identified to have been carried out the same way, creating the same hazards. These issues indicate a number of installers are not aware of the minimum safety requirements as set out in our regulations and standards and the safety risks created by these situations.

Potential risk

Where neutral continuity is not maintained there is the potential of causing a voltage rise on the installation earthing system and therefore imposing a voltage on any conductive medium that is connected to the installation electrical earthing system. In this situation a return path for fault currents has not been provided.

Where neutral and earth cables are installed in parallel there is a risk of conductors not being of adequate size to carry fault currents.

Requirements

• AS/NZS 4777.1:2016 Clause 5.4 covers the requirements for the installation of multiple mode inverters and references the alternative supply arrangements in AS/NZS 3000.including neutral continuity, earthing arrangements and correct operation of RCDs.
• AS/NZS 3000:2018 Clause 7.3.8.1.2 requires the change-over device for the alternative supply to maintain the continuity of the neutral conductor and operation of the RCDs.
• The Electricity Safety (General) Regulations [ES(G)R]2019 - Reg 208 defines the requirements for the installation earthing systems and MEN connection. The installation must have an MEN connection either:
  • at the main switchboard; or
  • at an earth bar or link within a substation; or
  • made through an earthing conductor or terminal provided by the electricity supplier.
    
    There are some exemptions in this regulation that relate to mine sites and installations not connected to an electricity supplier’s distribution system.
    
• AS/NZS 3000:2018 Clause 7.3.8.1.1(c) relating to alternate (Stand-by) supplies to an installation states 'Neutral and Earth conductors shall not operate in parallel'.
• These requirements are above the manufacturer’s installation instructions.

If the manufacturer’s installation instructions require other systems of earthing or neutral continuity they are not to be installed and further information must be sort from the manufacturer.

Energy Safe will be carrying out targeted audits of these types of installation to ensure they have been installed safely.

Testing to identify these hazards

Testing to verify the safety of the installation must be carried out by the Licensed Electrical Worker and the Licensed Electrical Inspector.

Firstly, mandatory verification testing must be carried out in accordance with Section 8 of AS/NZS 3000.

Additional testing should then also be carried out to verify the installation:

• Neutral & Earth conductors are not operating in parallel (no additional MEN connection within the inverter)
• maintains continuity of Neutral conductors.

Note: Some inverters may create an MEN connection internally when switching over to back up mode. This is not allowed in Australia and must be identified and disabled. Refer to your manufacturer for details on how to achieve this.

Important safety message:

The following tests are performed with the installation and equipment in the energised state:

• The Licensed worker must ensure a safe test procedure is followed in accordance with AS/NZS 4836 – Safe working on or near LV and ELV electrical installations and equipment
• Use appropriate PPE for the task: Eye Protection, LV Gloves, protective clothing etc
• Ensure the work area and installation are safe to proceed with the testing
• Ensure that occupants of the property are not put at risk.

Note: The additional testing should be carried out in the following order, with Test # 2 only conducted once Test # 1 is verified to ensure both issues can be identified.

Test # 1 - Test method to confirm MEN only at the main switchboard

Important - ensure you carry out this test in both the grid mode and back up mode.

Grid mode test

Using a clamp / tong tester set on Amps:

1. Ensure the Main Switch Normal Supply is ON, Inverter Supply Main Switch ON and Back Up Supply circuit breaker is ON, allowing the Inverter and Battery system to be powered up and operational.
2. Ensure the circuit breakers to the normal loads are OFF – lights, power, stoves, A/C etc off.
3. Ensure you have a load on the back up circuit, for example a kettle on, or a refrigerator running, etc.
4. Test for current flow in the Back up Active conductor.
   Record the result, for example – 2.0 A (total current flowing in the back up circuit).
5. Test for current flow in the Back up Neutral conductor.
   Compliant test result – Same value as recorded on the backup active.
6. Now test the current flow in the earth conductor connected to the main earth bar or M.E.N connection.
   Compliant test result : Zero (0) Amps

Note: If a current is recorded on the earth conductor, this may indicate an additional MEN connection within the inverter, causing the inverter earth and neutral to operate in parallel.

Back up mode test

Using a clamp / tong tester set on Amps:

1. Ensure the Main Switch Normal Supply is OFF, with the back up supply ON.
2. Ensure you have a load on the back up circuit, for example turn a kettle on, or have a refrigerator running, etc.
3. Test for current flow in the Back up Active conductor.
   Record the result – ie: 2.0 A (total current flowing in the back up circuit).
4. Test for current flow in the Back up Neutral conductor.
   Compliant Test Result – Same value as recorded on the backup neutral.
5. Now test the current flow in the earth conductor connected to the main earth bar or MEN connection.
   Compliant Test Result – Zero (0) Amps

Note: If a current is recorded on the earth conductor, this may indicate an additional MEN connection within the inverter, causing the inverter earth and neutral to operate in parallel.

Images courtesy of TechSafe Australia acting under the Solar Victoria battery audit program.

Above images shows the current flow through the Active conductor is divided between the Earth and Neutral conductors, indicating a Neutral / Earth connection within the MMI and allowing the Neutral and Earth conductors to operate in parallel.

Test # 2 - Test method to confirm continuity of neutral conductors

With your Multi-meter / Voltage Tester set on AC Volts:

1. Ensure the Main Switch Normal Supply is OFF, with the Back Up Supply ON
2. Test between the Main Earth Bar and the Back Up Neutral bar / conductors.
   Compliant Test Result : Zero (0) Volts
3. Now test between the Main Earth Bar and the Back Up Active conductors.
   Compliant Test Result : 230 Volts

Notes

1. If a voltage is recorded on the Back Up Neutral bar / conductors, this indicates the neutral conductors are not continuous to the Main Neutral.
2. Be aware – continuity testing between the Main Neutral Bar and the back up Neutral Bar may provide a pass test to indicate continuity in either the de-energised or grid supply states, but then may not maintain continuity when switched to the back up (Stand-by) modes.

Image Courtesy of TechSafe Australia acting under the Solar Victoria battery audit program.

The above image shows voltage tested on the Back Up Neutral Bar, indicating neutral continuity has not been maintained in the back up mode, recording a potential voltage of 82.9 V a.c.

Summary

• Carry out mandatory verification testing in accordance with Section 8 of AS/NZS 3000 - The Wiring Rules.
• Ensure the MEN connection is at the main switchboard (or compliant with the options as outlined in ES(G)R-r.208).
• Perform confirmation testing as detailed in this document to ensure Neutral and Earth conductors are not operating in parallel.
• Ensure neutral continuity is maintained from the Main Neutral to the circuits that are provided backup power either when connected to the grid supply or operating in stand-alone mode in the event of a grid outage.
• Do not follow the manufacturer’s instruction if they don’t comply with the requirements of the standards or the regulations.

Further information

The Electrical Regulatory Authorities Council (ERAC) has also published information relating to these requirements, see: Multiple_Mode_Inverters_Stand-alone_Operation (ERAC).

Relevant rules

Australian standards

Grid connection of energy systems via inverters Part 1: installation requirements

Clause 5.4

Additional requirements for multiple mode inverters.

Australian standards

The Australian/New Zealand Wiring Rules (AS/NZS 3000:2018)

Clause 7.3.8.1.2

Connection to electrical installation, alternative supplies, switching.

The Electricity Safety (General) Regulations [ES(G)R] 2019

Regulation 208 – Earthing systems.