Sub-Metering Systems – Are they any good?


Elcomponent MD Bill Gysin looks at getting real value from aM&T systems…

The simple answer to that slightly provocative question is of course “it depends” and it depends on quite a few key factors! If ever there was an energy management device that must be viewed in terms of a complete package, aM&T systems are that device. As good as their weakest link, and there are many links to consider. Elcomponent celebrates thirty years in the business this year, and in that everything has changed and everything has stayed the same! It’s a good time to take a brief look to guarantee that your investment in sub-metering pays immediate and substantial dividends…

The Data

It sounds obvious, but it still has to be stated that it’s the data that matters most, and it’s not just a question of accuracy, imperative as that may be. It has to be the right data, delivered at the right level of detail, and delivered reliably for years into the future with the minimum of maintenance. That is not just down to the right hardware and a good quality installation. Before those choices are made, the system has to be designed so that the meters are reading the right loads or supplies, ensuring that the picture thus obtained is easily understood and readily provides the information needed to save energy. And remember a lot of little savings is harder work and less effective than a few big savings!

The right data, but also the right frequency of data too ‘Half-Hour’ interval data is the UK norm and for good reason, it has been shown to be right in the ‘Goldilocks Zone’, but if your processes need more familiarity, make sure your system can provide it. Don’t consider anything that cannot at the very least provide ‘HH’ profiling, and whilst we’re on the subject of intervals, the data update interval is also critical. Systems that update their software on a ‘day plus one’ basis (i.e. the most recent data available is yesterday’s) shall provide good basic information but there is a whole lot they cannot do. As the demand for interactive dashboards continues to grow the case for realtime data becomes more and more compelling. You want to engage with a wider audience to footer a new awareness? That’s tough to do if the best you’ve got is yesterday’s data. If you would like to see alarms and alerts before, it’s too late ‘day plus one’ has its drawbacks too! The case for a 30 minute update to match the 30 minute meter read interval is not hard to make, and it’s entirely doable. Make sure the data acquisition system is fit for purpose and robust, there is no ‘one size fits all’ solution for this. The networking solutions should fit the requirements on the ground… cable is cheaper and more reliable than wireless links – until you have to dig up the car park. Tailored solutions work better and are far more cost-effective, and as the data is the foundation of the system, it’s worth spending time getting this element right.

The installation

Installing a sub-metering system isn’t rocket science, but it’s not easy either. We’ve lost count of the number of systems that we’ve replaced over the (30) years that never quite worked or sometimes didn’t work at all, and not all were badly installed by any means. They just weren’t installed and commissioned as well as they needed to be. No two installations are the same of course, but there are some common threads that bind them together. Most are a combination of our new and existing meters, most are multi-utility, and most involve a variety of meter outputs (pulse, MODBUS, M-Bus etc.). Almost all involve a tariff meter connection or two… An extensive list of what could go wrong would take up the remaining pages of this magazine, and would almost certainly try the patience of the readers who made it this far, but here’s a few of the more common pitfalls…

  • Pulse Values:

How hard can it be? Harder than it looks is the answer! The combination of ‘units per pulse’, ‘pulses per unit’ imperial units and metric units and the inaccessibility of some pre-existing meters means mistakes are easy to make. Religious attention to detail at bot installation and commissioning stages is the only antidote.

  • Incorrectly installed or programmed existing assets:

The world is full of meters that have been there for years and never worked properly!

  • Tariff meter data connections:
  • The professional sub metering/ AMR

Installer needs more than qualified staff. They must also hold MPU (Meter Pulse Utilisation) agreements with all the relevant Meter Operators, Meter Asset Managers and Utility providers to allow them to connect legally and properly to tariff meters.


Future Profiling

Nothing, it is said, lasts forever, and that is certainly the of M&T software. In fact there is a wider choice of software on offer now than ever before, and as a web based solutions become the norm new web tools allow functionality to be delivered by the latest products that in itself creates a need for portability at the data level.

This does not alter the fact that aM&T systems must be viewed as a package, but it does mean that all the important data must be readily transportable to whatever software solution fits the client’s needs now and in the future. It should be borne in mind that those needs may change.

Dash 1

Chart 1

Chart 3

The Software

Notwithstanding the desirability of ensuring portability of data, if the right choice is made in terms of software there should be no need to change – at least for many years into the future.

The core requirements for effective energy management haven’t hanged, the need to address a wider, and not expert audience has.

Traditional functionality must include easy normalisation of data (one click preferably) because there is a limit to how much can be achieved through waste elimination and the honesty of traditional ‘low hanging fruit’. At some point the impact of degree days, floor area, occupancy and production (to name but a few) must be assessed, and it must be easy to do.

Similarly, regression analysis must be present to provide additional power to the more usual presentation of consumption and profiles. Measurement and verification (M&V) is a relative newcomer but it is increasing by a standard in a repeatable way, and is a requirement of ISO50015.

Without the above functionality hard-core energy management cannot be done, so it has to be present, but there are now other ways in which good software is being used to improve energy and carbon performance. The umbrella often used is ‘behavioural change’ and it addresses the biggest challenge of them all – the impact of people on that performance. It is people who override controls designed to optimise energy use, it is people who switch on heaters and open windows, and it is people who often are the reason for the gap between expected and actual performance in energy terms.

The jury may still be out on the best way to encourage a workforce or users of a building, but one thing is certain – providing accurate and relevant information in simple and accessible form is a key component, and the right software can do that key effectively. It must be accessible which means no (or low) user charges – it must be friendly and it must be accurate.

With those criteria met, M&T software find itself at a whole new audience and a new role. It has to be up to the task.

For more information contact:

01279 503 173


About Author

Comments are closed.