The importance of sub metering systems

The importance of sub metering systems

Sub metering is often considered to be a relatively small part of a multi-let new build / re-development project. As a result, it is usually addressed at a later stage as part of the wider electrical and mechanical systems and is not given the attention it deserves, according to Carbon2018.

The energy management consultants argue that without access to data relating to the quantity and distribution of energy usage across a site, it is not possible to effectively manage and minimise energy usage, nor accurately recharge tenants for their proportion of the total energy consumption. Failed or inadequate metering systems present property managers with a number of risks, not least the impact this has on cash flow where there is an inability to recover the costs paid out for energy from tenants.

Due to the importance metering has on operations, it is necessary to take a comprehensive and joined up approach to the metering strategy which needs to start at design stage and be followed through to commissioning and building completion. Input needs to be given from all of the building stakeholders throughout the process. Getting the metering design, installation and commissioning right prior to practical completion saves unnecessary cost and hassle further down the line.

One example of the types of problems encountered is a new build, mixed use, multi-occupied property Carbon 2018 surveyed in the West End. Due to the building’s mixed use nature, it would not have been equitable to recharge electricity, heating, cooling or water costs proportional to the square footage occupied due to the different operating hours and loads placed on the system by the range of occupiers. Therefore an extensive metering system was installed comprising electrical, heating, cooling and water sub meters. However, upon inspection, more than 80% of the mechanical meters had problems including oversized meters which were therefore under recording, meters installed at the incorrect orientation to be able to record accurately, and a lack of commissioning of heat meters meaning that temperature probes and flow parts were located in the wrong pipes. The remedial work undertaken to get the system to a standard where it could be used for accurate tenant billing and management of energy in this complex building cost over £200k and included several meter replacements.

Metering needs its own full design, specification and commissioning specialist . It shouldn’t be tucked away into three pages of a 300 page electrical and mechanical specification. It also needs to be recognised that whilst electrical and mechanical designers and installers are extremely good at what they do, they are not generally specialists in metering.

All too often, metering strategies are based on meeting Part L of the building regulations, however, building regulations set only a minimum standard. Each metering strategy should be tailored to the specific requirements of the project – cutting and pasting from one specification to another will guarantee that things are missed, or as we have seen in many cases, results in a jumbled ‘shopping list’ of requirements which are not even compatible with one another.

Ahead of installation, consideration also needs be given to the type of meters required. There are a myriad of meters on the market. The assessment must include factors such as the registers from which you wish to record the data, whether MID approval is required and the size of the supply and location. Whilst cost is also a factor, this should not be at the expense of addressing what is required to meet the objectives. We have witnessed numerous occasions where the cheapest heat meter option has been sought, which entails purchasing a standard low accuracy water meter as the flow part and bolting this together with a heat meter calculator. However, this solution can result in issues with compatibility between meters and data accuracy problems and consequently nearly always ends up with the meters being abandoned or replaced. The introduction of the Heat Network (Metering and Billing) Regulations in 2015 means that where heat meters exist in multi-let buildings with communal heating and cooling systems (or for district systems), there is a legal requirement to maintain them and use them for billing.

Until recently, many metering systems saw no commissioning at all and issues were only identified once the system was in use. This must include checking for the correct installation and setup of the meters themselves, point to point testing of the connectivity between the meters and AMR system, validation of the data on the AMR head end again meter registers, review of documentation and testing of the communications for remote access to data.

In summary, implementing a best practice approach to metering which uses the objectives to inform the strategy, incorporates all relevant stakeholders’ views and includes regular reviews/updates as required throughout the project lifecycle will result in a system which delivers and meets the needs of building stakeholders once the site is operational.

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