A6M+One Selection and Pre-Installation Comprehensive Guide

This guide intends to support purchasers, owners and installers of the A6M+One single- and three-phase billing solutions to effectively plan and purchase the bundled hardware.

A6M+One Selection and Pre-Installation Guide

Solutions for single-phase and three-phase billing applications


Introduction

This guide is intended to support purchasers, owners and installers of the A6M+One single- and three-phase billing solutions to effectively plan and purchase the bundled hardware.


Please refer to the A6M+One (6M4/MB) Installation Guide article for information on how to install the equipment.

Important Information

  • You must select the correct meter type for your application. Refer to the Solution Selection Guide section for more information.
  • The CTs used for the CET Meter and Wattwatchers Auditor devices are NOT compatible or interchangeable and may cause damage or create a hazardous situation if installed incorrectly.
  • If you wish to monitor non-billing circuits, then you need to order the correct sized Current Transformers for the Wattwatchers Auditor device separately.

What is the A6M+One?

The Wattwatchers A6M+One billing solution combines the Wattwatchers Auditor A6M 4G device with an Australian NMI M-6 Pattern Approved revenue meter to provide billing data in 5 minutes resolution and additional non-billing circuit monitoring capability for applications such as:

  • Solar Large-scale generation certificate monitoring (LGCs)
  • Solar Power Purchase Agreements (PPAs)
  • EV charging monitoring
  • Embedded networks
  • Microgrids

The A6M+One billing solution is a compact, DIN-rail mounted bundle in either single-phase or three-phase configurations. Each bundle includes:


  • 1x Wattwatchers A6M 4G device with Modbus interface for connection to the CET billing meter and supporting monitoring of up to 6 circuits for non-billing applications
  • 1x CET NMI M-6 pattern approved revenue meter in one of the following configurations for billing applications:
    • Single-Phase Direct Connect Meter, or
    • Three Phase Direct Connect Meter, or
    • Three Phase Current Transformer Meter.

It is important to be aware that for all options, the included CET meter is capable of measuring one billing circuit only. For example, this may be the output of a single-phase inverter or the total output of multiple inverters at the Solar Supply Switch.


Should you need to monitor more than one billing circuit, then a separate A6M+One bundle will be required for each additional billing circuit.

Solution Selection Guide

Use the following solution selection guide to choose and order the correct configuration for your application.


Application

A6M+One Bundle

Included Products

Single-Phase applications up to 63A

A6M+One Single-Phase billing bundle

1x A6M+One (6M4/MB)

1x CET PMC-220

Three-Phase applications up to 100A per phase

A6M+One Three-Phase Direct Connect billing bundle

1x A6M+One (6M4/MB)

1x CET PMC-340-BA

Three-Phase Current Transformer applications up to 600A per phase

A6M+One Three-Phase CT billing bundle

1x A6M+One (6M4/MB)

1x CET PMC-340-BB

3x 600A/5A CTs


A6M+One Single-Phase billing bundle

The A6M+One Single-Phase billing bundle includes:

  • 1x Wattwatchers A6M+One (6M4/MB)
  • 1x CET PMC-220 Single-Phase Billing Meter

This version of the solution is suitable for use with a billing circuit rated up to 63A and wire size up to 25mm2 cross-sectional area (2.8mm wire diameter). 


The billing circuit cables are connected directly through the CET meter without the use of any external current transformers (CTs).


This solution requires at least a total available space of 4 poles (71mm) width on a 35mm DIN rail for the A6M+One (6M4/MB) (2 poles ~35mm) and the CET PMC-220 meter (2 poles ~36mm). 


The A6M device should also be installed with a single-phase 6A breaker or RCBO for protection and isolation of the power and voltage reference connections as per the local jurisdictional requirements. 


The CET PMC-220 meter is rated for 63A and should be protected by an upstream main switch or fuse with the same or lower rating.


For detailed technical information on the CET PMC-220 meter, please refer to the User Manual.

A6M+One Three-Phase Direct Connect billing bundle

The A6M+One Single-Phase billing bundle includes:

  • 1x Wattwatchers A6M+One (6M4/MB)
  • 1x CET PMC-340-BA Three-Phase Billing Meter

This version of the solution is suitable for use with a billing circuit rated up to 100A per phase and wire size up to 35mm2 cross-sectional area (6.6mm wire diameter).


The Single-Phase and Three Phase direct-connect versions of the solution are suitable for use with a billing circuit rated up to 100A per phase and wire size up to 35mm2 cross-sectional area. 


The billing circuit cables are connected directly through the CET meter without the use of external current transformers (CTs).


This solution requires at least a total available space of 9 poles (161mm) width on a 35mm DIN rail for the A6M+One (6M4/MB) (2 poles ~35mm) and the CET PMC-340 meter (7 poles ~126mm). 


The A6M device should also be installed with a three-phase breaker or RCBO with a rating of ≤ 16A for protection and isolation of the power and voltage reference connections as per the local jurisdictional requirements. The breaker or the RCBO is not included as part of the Wattwatchers bundle.


The CET PMC-340-BA meter is rated for 100A and should be protected by an upstream main switch or fuse with the same or lower rating.


For detailed technical information on the CET PMC-340 meter, please refer to the User Manual.

A6M+One Three Phase CT billing bundle

The A6M+One Single-Phase billing bundle includes:

  • 1x Wattwatchers A6M+One (6M4/MB)
  • 1x CET PMC-340-BB Three-Phase Current Transformer Billing Meter
  • 3x 600A/5A Current Transformers

The CET PMC-340-BB billing meter is suitable for use with a billing circuit rated up to 600A per phase. This version requires separate 600A split-core CTs specific to the CET meter that are included with this bundle. Details of billing CTs are given in the table below.


CET Meter Current Transformer Specifications

Size (Amps)

Max circuit rating / CT output ratio

Opening Width (mm)

Max conductor size inc. insulation (cable or busbar)

Cable length (m)

Max cable distance from CET meter to CT

600A / 5A

36 mm

2.8 m


Extension of the billing CT cables should be avoided and the existing length should be treated as the maximum allowed from CET meter location to where the CTs are clasped over the billing circuit conductors.


This solution requires at least a total available space of 9 poles (161mm) width on a 35mm DIN rail for the A6M/4/MW (2 poles ~35mm) and the CET PMC-340 meter (7 poles ~126mm). 


The A6M and CET PMC-340-BB device should be installed with a three-phase breaker or RCBO with a rating of ≤16A for protection and isolation of the power and voltage reference connections as per the local jurisdictional requirements. The breaker or the RCBO is not included as part of the Wattwatchers bundle.

Consideration should also be made to install a CT disconnect and test block to allow for any future testing or maintenance of the CET meter to be performed without an outage or interruption to the billing circuits. This is not included as part of the Wattwatchers bundle.


Note that it is possible to use CTs with a higher rating than 600A, but these are not supplied by Wattwatchers and additional configuration changes in the field will be required. Please contact the Wattwatchers sales team or contact Wattwatchers Support for additional information.


For detailed technical information on the CET PMC-340 meter, please refer to the User Manual.

Access to billing data

The energy consumption data from the CET billing meter is transmitted to the Wattwatchers platform by the Auditor 6M device over 3G/4G and is then made available via the Wattwatchers API.


Data from the CET billing meter is not currently available in the Wattwatchers Dashboard web portal application and must be consumed from the Wattwatchers API or one of our billing solution partners.


If data from the billing circuits is required to be accessed from the Wattwatchers Dashboard, then it is recommended to monitor the same billing circuit with both the CET billing meter and the additional Wattwatchers non-billing circuit monitoring functionality. This would require the non-billing CTs to be connected to the A6M+One (6M4/MB).

Additional non-billing circuit monitoring

For each of the A6M+One billing solutions, the CET meter must monitor the billing circuit. The Wattwatchers A6M provides the 4G communications for remote monitoring of the CET meter and also has its own non-billing submetering capability for up to 2x three-phase circuits or up to 6x single-phase circuits. This would require the non-billing CTs to be connected to the A6M+One (6M4/MB).


Use of the metering inputs on the Auditor 6M requires additional Wattwatchers split-core CTs to be installed for each input to be monitored. These are available in sizes ranging from 60A to 600A and must be ordered separately if required.


Electricians may extend the non-billing CT cables up to 10m total in length, or shorten cables if necessary. However, this should be avoided where possible.


If you require additional monitoring than the single Auditor allows, or to monitor circuits further than the recommended cable length, then additional independent Auditors can also be individually purchased. 


Wattwatchers Auditor Current Transformer Specifications

Size (Amps)

Max circuit rating / CT output ratio

Opening Width (mm)

Max conductor size inc. insulation (cable or busbar

Cable Length (m)

Nominal cable length from CET meter to CT

Maximum Cable Length (m)

Max cable length from CET meter to CT

60 A / 80 mA

10 mm

1.6 m

10 m

120 A / 100mA

16 mm

1.6 m

10 m

600 A / 100mA

36 mm

2.8 m

10 m



A number of product bundles have also been prepared to assist in ordering based on the common size ranges of solar systems. Please see the following table to assist with ordering all equipment to monitor both the billing and non-billing circuits.

Product Bundle (kVA)

System Size (kW AC)

System Phases

Non-billing CT Size

Billing Meter

Billing CT

8.2

Up to 10

Single

60A/100mA

PMC-220

None

72

41-70

Three

120A/100mA

PMC-340-BA

None

430

131-430

Three

600A/100mA

PMC-340-BB

600A/5A


So for example, if you are installing this solution on a Three Phase 99kW Solar System, then the 430kVA bundle provides the necessary hardware to monitor the solar generation for both billing and non-billing purposes.


Please also refer to the Wattwatchers A6M+One Quick Start guides for more information on the installation requirements and capabilities of this device.

Warning on CT Compatibility

The Current Transformers used for the CET Meter and Wattwatchers Auditor devices are NOT compatible or interchangeable.


The CTs used for Wattwatchers Auditors (including those for 600A primary input) are rated to provide 100mA output and are NOT compatible CET meter inputs.


The 600A/5A CTs used for the CET meter are rated to provide 5A output and WILL cause damage if these are wired into the Wattwatchers Auditor device. The output of the 600A/5A CTs must not be disconnected or left open-circuit when the primary circuit is energised as dangerous voltages may be present and may create an electric shock or electrocution hazard.

Purchasers and installers must ensure they do not mix up the 600A/5A billing CTs and the non-billing CTs. The current ratio should always be double-checked on all CTs prior to installation and during device commissioning.


Wattwatchers does NOT warrant damage to hardware caused by improper installation where an installer has failed to follow all instructions as directed, mishandled or wired components incorrectly, used parts for an unintended purpose, or used alternative unapproved parts (e.g. CTs). All warranties will be voided under these conditions. 

Preparing for installation

Coordinating any installation effectively requires purchasers, owners and electrical installers to communicate clearly with one another during the project.


The checklists below are recommended to assist through this process, to prompt necessary checks and details for discussion and as a useful record keeping tool.


Please refer to the pre-installation checklists attached to this article.


Example Checklist

  • Owner or purchasers pre-installation checklist example (to be added)
  • Electricians pre-installation checklist example (to be added)

CET Meter Documentation

More information or support

Our technical team is available for urgent matters (such as where an installer is actively troubleshooting onsite) from 09 AM to 5 PM, Monday to Friday, AEST/AEDT on 02 8316 7540 (+61 2 8316 7540 from overseas).


For all other enquiries, please first check our Support Page.