This month, MWA Technology feature in EIBI magazine with an article for Monitoring & Metering. MWA Technology MD Martin Wardell detailed the potential pitfalls of meter selection in a time where thousands of meters are being incorrectly specified and installed in buildings throughout the UK.
Too many consultants and specifiers are not paying enough attention to selecting and specifying meters. Poor implementation of submetering, made worse by no clear understanding of how to use it properly and the benefits it can bring when done properly is leading to problems.
Regarding the choice of meters for monitoring purposes our mantra is to follow what the practices that the UK water, gas, thermal (heating & cooling) and electricity utilities follow.
While many consultants specify water meters to be MID certified, they rarely specify the MID ratio which indicates the accurate range of the meter. UK water utilities choose water meters with a minimum of R400 which represents the ratio between the continuous flow rate and the minimum accurate flow rate. Furthermore all UK water companies no longer use water meters “reed switch” pulse output devices. These have been found to become unreliable and have led to over reading at low flow rates and under reading at high flow rates. Generally most water meters operated by such companies when a pulse output is required use encoded pulse sensors such as the Itron Cyble or Elster PR6/7 units.
Single-jet and multi-jet meters generally have relatively low MID ratios and are also sensitive to correct installation which means that they must be such that they are only installed in horizontal pipe runs with their indexes facing upwards. Any other installation results in poor performance or the meters stopping at certain flow rates. UK water companies do not use multi-jet meters.
Regarding gas meters, selection based on the UK gas utilities criteria will ensure that meters are selected with a minimum low pressure drop and are suitably matched to the range of flow rates to be encountered by the meter. Oversizing of gas meters to ensure compliance with IGEM UP/2 pressure drop requirements can result in meters being inaccurate at lower flow rates or may not even record consumption at all. This is particularly relevant to turbine gas meters, Quantometers, some of which not only exhibit high pressure drops at certain flow rates but also have relatively low turndown ratios.
Generally diaphragm meters and rotary meters are MID certified. However, Quantometer is a variant of fiscal turbine gas meters and are not certified to MID standards. Unlike the rest of Europe there has been a tendency in the UK to install thermal energy (heat meters) based on conventional paddle wheel water meters which is not a common practice in mainland Europe. The use of such water meters leads to an unreliable energy metering system. The use of low grade water meters results in premature failure of the metering system after a relatively short period of time. Thermal energy (heating & cooling) meters should be based on proven solid state ultrasonic or vortex shedding technology which will give many years of accurate performance. Such meters should ideally be supplied by a single manufacturer and certified to MID Class II.
There is also growing concern that building services contractors are also choosing meters on “cost over quality” with little regard to the
anticipated accurate operating life of the meters as they look to meet budgets and time pressure on their projects for the major contractors.
Expensive data collection
With the drive towards sustainability, energy usage and carbon emissions reduction buildings are having sophisticated and expensive data collection and display systems installed so that managers can constantly monitor energy consumption and using this information look to control usage and minimise wastage. This information is only as good as the meters from which it is gathered. It is well known that many contractors are more concerned about the short-term performance of meters – as long as they work for a year – that is fine. It is then the operator of the building “who picks up the pieces” and is faced with the expensive task of replacing meters in an operation building.
Talk to any of the energy and estates managers in many of the universities throughout the UK and they know that many of the buildings that they operate have required meters replacing only a short period of time had elapsed after the buildings had been handed over. Quality is long remembered long after price has been forgotten. This is a mantra that the sector seems to be dismissing at the moment, as we see a huge surge in the number of projects with failing meters sometimes only a few months after handover. When quizzed some project managers have said it is to do with depleted budgets or that all I need the meters to do is “work” for a year and a day.
The rule of thumb is to follow the practice of UK utilities and to install “utility grade” meters as you can trust their accurate operation and the data they generate for a minimum of 15 years.