Meeting metering standards

When it comes to adhering to the EU’s strict carbon emission reduction targets and qualifying for the Government’s Renewable Heat Incentive (RHI) scheme, metering accuracy plays a pivotal role as Trevor S. Palmer, Managing Director at Sontay, explains.


With precise and reliable metering acting as one of the primary tools for proving that the building services sector can minimise fuel consumption and cut energy costs in-line with new targets, accuracy and meter intelligence is now even more important than ever.


However, during 2013 we have highlighted the inherent need for an improved process when specifying, selecting and commissioning heat-metering systems specific to the application. We went on to predict that without a drive in detailed metering tuition (led by either Government or industry figures) building occupiers would continue to achieve disappointing, inaccurate and unreliable heat-metering results.


Yet, progress on these fronts remains disappointing.


Lack of detail


Unfortunately, we are beginning to see the consequences of an industry devoid of proper industry-led heat metering guidance. A report Ofgem published last year noted that close to 40% of all RHI applications are delayed because of a lack of detail about system capacities, heat-meter compatibility or missing schematics. It went on to suggest that not only had around 25% of applications failed to provide basic details about their meters, but that when sites were audited by Ofgem, many meters had not been installed correctly, resulting in the suspension of payments to some users.


On 24 September last year, the Department of Energy and Climate Change (DECC) made changes to the non-domestic RHI, which affected heat metering. The amendments were aimed at simplifying the process and to increase the uptake of the scheme. The changes eased metering requirements and meant only a minimum number of meters were necessary to calculate the RHI payment. In certain circumstances, they also allowed heat loss from external pipework to be disregarded where it could be considered that it was properly insulated. In addition, applicants who could prove that it is either physically or financially overly burdensome to install a heat meter, would instead be allowed to submit a heat loss calculation in place of installing additional meters.


Making the heat metering process easier is a step forward but it is far from the end of the story.


Inadequate specification


Metering in the UK remains an area typified by inadequate specification, poor installation techniques and a lack of knowledge that completely compromises the performance of the meter itself. Let me explain why.


First, let’s take a look at the legislation. The 2010 Building Regulations requires reasonable provision for the installation of energy meters in buildings with a floor area greater than 1000sqm and which enable at least 90% of the fuel to be assigned to the various end-use categories (heating, lighting, etc). Following CIBSE Guidance TM39: Building Energy Metering is advised to ensure best practice.


Meanwhile, the European Commission’s Measuring Instruments Directive (MID) is also important. Approval to MID is required for meters used in any billing application, including heat and water meters, with instruments having to meet the general essential requirements of the directive plus one of ten instrument-specific annexes. With the MID European Type Approval Certificate, an instrument may be freely sold and used in any European country. MID and the harmonised standard EN 1434 (which is widely used to prove compliance) deals not only with meter compliance but with the requirements for installation and maintenance.


So far, so good. The problems are in the detail of what actually happens on site. Problem one (as seen in the Ofgem report) is that the wrong meter is often used for an application.


Broadly speaking, there are two types of products; flow parts for water (water meters) and flow parts for heating (flow sensors). It is the latter that should be used for heat metering not the former. Far too frequently, this is just not the case. Too many building services engineers simply select and install meters on price alone and not on whether the meters themselves are actually correct for the application.


Inaccurate measurement


Heat meters comprise three parts; a flow sensor to measure volumetric flow, a pair of matched temperature sensors and a calculator. Many engineers are confused about flow meters designed for non-continuous flow (such as water meters) and those intended for continuous flow. Water meters made for non-continuous flow typically have an upper temperature limit of +90°C and are generally limited to flow not exceeding three hours per day over a six year period. Flow sensors for heat meter applications typically have an upper temperature limit of +130°C and are designed for 24 hours a day, every day continuous flow. Water meters, if used in heat-metering applications (i.e. high duty or continuous flow) are unlikely to retain the accuracy over the normal five year lifespan of the product and should not therefore be specified or installed.


Specifying a water meter that is designed for non-continuous use and paired with a MID approved heat-meter integrator will render any installation inaccurate and irrelevant.


An MID approved integrator must be connected to a flow sensor to ensure accurate measurement and billing. MID product approval is determined by the international metrology institute, the PTB (Physikalisch-Technische Bundesanstalt). Any changes made to the integrator must be carried out at a PTB approved laboratory. If modifications are carried out in the field, as they frequently are (such as reprogramming of an integrator), then the integrator is no longer accurate, will not meet the MID compliance requirement and cannot be used for billing purposes.


Metering is not a one-size-fits-all kind of business. Far from it.  Since the use of unapproved meters for billing carries a potential risk of prosecution, contractors and consultants have a responsibility to ensure that their clients have compliant meters fitted for the right application. An industry source I came across recently claimed that 90% of meters presently fitted in commercial buildings are not compliant for billing purposes. Our own experience at Sontay makes me fear that this figure, unlike the numbers recorded by the vast majority of UK metering installations, is, regrettably, an accurate one.


In order for the Government’s RHI scheme to fully take flight, it is important that applications must be easy to fill in and quick to be accepted. Yet, without the adequate precision guaranteed by properly installed and specified heat-metering devices, building occupiers will be more likely to make mistakes in their heat-data calculations, resulting in delayed or withdrawn payments, and an inadequate system for all concerned.

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