The UK's approach to metering is farcical and needs to change, says Trevor S. Palmer
Minimising fuel consumption and cutting energy costs remain the fundamental priorities for the building services sector and the vast majority of its clients. On that we can all agree.
But how do we actually prove that we are delivering on these objectives? Accurate and reliable metering is surely the answer. If only it were so simple.
Metering in the UK is an area typified by inadequate specification, poor installation techniques and a lack of knowledge which 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 require reasonable provision for the installation of energy meters in buildings with a floor area greater than 1,000 sq m and which enable at least 90 per cent 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 also with the requirements for installation and maintenance.
Trevor Palmer: 'Inadequate specification'
So far, so good. The problems are in the detail of what actually happens on site. Problem one is that the wrong meter is often used for an application.
Broadly, there are two types of products; flow parts for water (water meters) and flow parts for heating (flow sensors). It is the latter which 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 lowest cost alone, and not on whether the meters themselves are actually correct for the application. 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 designed for continuous flow. Water meters designed for non continuous flow typically have an upper temperature limit of +90 deg 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 deg 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.
Using a water meter designed for non-continuous use paired with a MID-approved heat meter integrator will render any installation inaccurate and irrelevant.
A 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 - www.ptb.de).
Any changes made to the integrator must be carried out at a PTBapproved laboratory. If changes are carried out in the field, such as reprogramming of an integrator (as they frequently are), 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. Contractors and consultants have a responsibility to ensure their clients have compliant meters fitted for the right application, since the use of unapproved meters for billing carries a potential risk of prosecution. An industry source recently claimed that 90 per cent of meters presently fitted in commercial buildings are not compliant for billing purposes. Our own experience makes me fear that this figure, unlike the numbers recorded by the vast majority of UK metering installations, is, regrettably, accurate.
There needs to be a vast improvement in specifying, selection and commissioning of heat metering applications to ensure that the correct information is being derived from these meters and, more importantly, that the building occupiers are being billed correctly. Who is going to take responsibility?
// The author is managing director of Sontay //