Inferior submetering is destroying performance

Poor design, specification and commissioning of submeters is costly, says Joanne Merry

Good submetering is critical if building owners, managers and occupiers are truly to manage building energy performance. On new-build and refurbishment projects, Building Regulations typically require electrical submetering for key areas and equipment. The introduction of the Heat Network (Metering and Billing) Regulations 2014 (HNR) has increased the number of properties requiring heat meters to be installed.

New-builds are becoming more complex, with integrated technologies, renewables and onsite generation – and the more complex a building is, the more intricate metering systems it requires.

The operational requirements of metering systems have also evolved. Under Part L, the focus was on monitoring, but metering now needs to meet the requirements for participation in schemes such as the Renewable Heat Incentive (RHI) to monitor the efficiencies of such technologies and plant. Technological changes, including advances in automatic meter reading (AMR) systems, have made possible real-time data through a variety of communication protocols.

Regulation in the guise of Part L and HNR may stipulate what needs to be metered, but it fails to explain how to do it, and doesn’t address all the challenges and objectives a modern metering system needs to cover. CIBSE’s revised TM39 Building energy metering – soon to be published, but first issued in 2009 – is timely. The guide sets out a modern methodology for metering for those involved in designing, specifying, installing or using new metering systems.

Remedial works often cost more than the installation of the original system

Submetering is often considered a relatively small part of a project, so it is usually addressed at a late stage and as part of the wider mechanical and electrical (M&E) systems – it is not always given the attention it deserves. From an operational perspective, failed or inadequate metering systems present several risks for property managers, not least the impact on cashflow if the energy costs paid out by tenants cannot be recovered.

A comprehensive and joined-up approach to metering is needed, starting at design stage and going through to commissioning and completion. Input from all building stakeholders is critical. Getting the design, installation and commissioning right before practical completion saves unnecessary cost and hassle further down the line.

We have seen several projects on which remedial works have cost more than the installation of the original system. Issues have included incorrect types of meters, inaccurate recording because of poor installation, and a lack of system commissioning.

Metering must be treated as a specialist system in its own right, rather than as an add-on to the M&E systems. It requires its own design, specification and commissioning processes, so engaging with a metering specialist is paramount.

At design stage, the strategy must be informed by the building stakeholders’ objectives. All too often, metering is based on regulatory demands and not tailored to specific requirements of the project, leading to a jumbled ‘shopping list’ of incompatible requirements.

Meter type should be addressed ahead of installation, and the assessment must include: the registers from which recorded data is needed – for example, kWh only, voltage, amps or reactive power; whether Measuring Instrument Directive approval is required; the size of supply; and location. Cost is also a factor, but should not be at the expense of requirements that meet the objectives. Going for the cheapest option often ends up being the most expensive when meters have to be replaced. On numerous occasions, we have seen the cheapest standard, low-accuracy water meter bolted to a heat-meter calculator. This can result in issues with compatibility, as well as data inaccuracy, and nearly always means meters are abandoned or replaced.

Where heat meters exist in multi-let buildings with communal heating and cooling systems, or for district systems, there is a legal requirement under HNR to maintain and use them for billing. Abandonment is impossible, and the only option is remedial works.

The final piece in the jigsaw is ensuring correct installation and commissioning of meters so they record accurately. This must include checking for: the correct installation and set-up; point-to-point testing of the connectivity between the meters and AMR system; validation of the data on the AMR head-end against meter registers; review of metering documentation; and testing of the communications for remote access to data.

Metering that uses the objectives to inform strategy, incorporates stakeholders’ views and includes regular reviews/updates throughout the project, will result in a system that meets the needs of the building users.

  • Joanne Merry is technical director at Carbon 2018