There are a variety of meter types and models. We have discussed that meters can be STS or AMI. However, within these two technology methods there are various types or models of devices. Each is designed for specific electrical requirements and environment. Deciding which equipment is best for your circumstances depends on the following:
- Does each section have its' own Distribution Board?
- Is the supply to the section Single Phase or Three Phase?
- If Three Phase; how many Amps per phase?
- Is there a high risk of tampering with meters?
Naturally, the ultimate issue is one of the capital investments of buying the equipment. So, while a consultant may offer an equipment specification, the cost of purchasing the recommended devices may be prohibitive. In this case the body corporate needs to make a decision whether to find a way to finance the equipment or to settle for a lesser specification than that which was recommended.
Explaining which meters to choose for AMI is the simplest and so we will cover AMI first.
AMI meters are generally the same; they are just very clever meters that can be read remotely. Small differences in equipment will differentiate various manufacturers, but the general overall idea remains the same. AMI meters do not use keypads, so they are generally installed in a central location. Without splitting hairs, this means that choosing an AMI device is much easier.
The only difference to consider is whether the AMI device has inbuilt intelligence for prepayment or not. While it will not make a huge difference because the prepayment system will balance all accounts and meters over time, there is a more immediate level of accuracy related to an AMI device that has intelligence for prepaid. This is because an inbuilt intelligence for prepayment ensures that there is a disconnect command from the meter itself. This means that there is no chance of the meter allowing the customer account to run into any amount of arrears which a prepayment system would balance off of any future payments the customer makes.
When choosing an STS device further considerations are required. STS metering solutions generally come in two types:
- Single Unit Devices
- Split Unit Devices
Single Unit Devices is a single housing device that may vary in size, and includes the meter, keypad and LCD display. Split Unit Devices are comprised of the meter as one component and the keypad/LCD as another component. Split Unit Devices therefore have a physical advantage over Single Unit Devices because the meter component can be remotely located from the Keypad/LCD. This is useful when you have an environment where tampering with the meter in order to by-pass billing is a problem. While most Single Unit Devices do have Tamper and Significant Reversal detection, these mechanisms only protect the meter device; they do not protect the distribution board which is another source of by-pass.
When using Single Unit Devices it is recommended that protection for the distribution board is also provided. One method to do this is to use lead seals to present opening of boards. The lead seal should have a stamp mark that is difficult to replicate. Single Unit Devices are perfect for retro-fit situations and are normally cheaper to purchase and install. So they are generally the option of choice in an existing situation.
The reality of every system is that it is subject to abuse. In the case of prepaid it is just a question of how long before you detect this abuse. This why the PrepaidMeters.co.za prepayment system provides a method based on Standard Deviation to help identify potential problems. Split Unit Devices are generally more expensive to purchase than Single Unit Devices. They can also be more expensive to install in a retro-fit situation simply because a twin flex wire must be used to link the meter component with the remote located keypad/LCD. Factors such as distance from meter housing box to the keypad/LCD and the complexity of the path leading between these two points have always been the key factor impacting on installation costs. Often these factors make the better choice of using Split Units prohibitive.
To overcome the costs of installation related to Split Units a new technology called Power Line
Communications (PLC) was introduced. This technology uses the existing electrical wires as a means to establish communications between the meter and the keypad/LCD. While this solution does eradicate the cost factors associated with running the communication wire between the two end points, it makes the cost of the actual devices more expensive. As a result, what you would spend on a normal installation of non-PLC Split Units will be paid in technology costs within the meter devices itself.
Meter Features that You Must Have
In addition to the above variants one also has to consider that some meters can be supplied without certain features. The following features can be options:
- Significant Reversal (SRE)
- Mains Over Voltage (MOV)
- Optical Port Interface (OPI)
In general when it comes to Tamper, SRE and MOV you do not want to cut corners in order to cut costs. However, when it comes to OPI you may consider a cost reduction if there will never be a need for data collection using a Remote Access Terminal.