Implementing a best practice approach to metering for the Crown Estate
1 & 2 St James’s Market, a joint venture between The Crown Estate and Oxford Properties comprising 2 buildings, has created 210,000 sq ft of modern office accommodation, six flagship stores and seven restaurants, all set within over an acre of revitalised public spaces, including a new public square and art pavilion. The development project included the installation of a full metering system both to comply with Part L building regulations, and to meet the operational requirements of the property post completion. Carbon2018 was commissioned as metering consultants to ensure the system delivered met operational requirements.
The metering strategy review requirements throughout all stages of the project were clearly defined at the outset (see figure 1).
Figure 1: Metering Strategy Review Requirements and Definition of Responsible Parties
Step 1: Objectives – Determining the desired outputs
The objectives and desired outputs must be the starting point underpinning any metering strategy if it is to be successful. It was therefore necessary when setting out the objectives to engage with all stakeholders including the design team, main electrical and mechanical contractor (and the appropriate sub-contractors), the managing agent and metering consultant Carbon2018.
Step 2: Select the Metering Boundary
As the site comprised of 2 properties and a public square, it was important to ensure that energy usage was captured across the whole site inclusive of the external lighting for the public square. The scope of metering was agreed to encompass electricity, gas, heating, cooling and water metering for the services which fall within the boundary line (see figure 2).
Figure 2: Graphical Representation of Metering System Boundary (plan not to scale)
Steps 3-4: List all energy imported and exported across the boundary and all energy using items within the boundary
It was necessary to review and understand the flows of energy within the properties to inform the strategy. Each of the 2 buildings has its own separate incoming utility supplies and central plant services – from an energy perspective there is no cross over between the 2 properties. Both buildings benefit from Photovoltaic (PV) solar panels located on the roof, and 1 St James’s Market also has a Combined Heat and Power (CHP) unit so there is generation of power locally onsite. The capacities of this equipment have been set such that they are sized to support the buildings’ baseload power, and there will be no export of power back to the grid. The only energy crossing the boundary is therefore from the incoming gas supply and grid power supply to each block which supplements the onsite generation. There is no energy exported back across the boundary as this is used internally.
A list of the main end use categories internal to the boundary was developed and the typical energy flows through the building identified (see figure 3). This included looking at inputs and outputs of central plant where transformation of primary energy to secondary energy takes place.
Following the energy flows through, it was clear that the CHP adds some complexity to the meter requirements within the building as gas is used onsite to generate both heat and power and the quantities of each generated needed to be tracked.
Figure 3: Main Building Energy Flows – 1 & 2 St James’s Market
Step 5: Decide Which Items to Meter
Having established the main energy flows, consideration was given to the items to be metered. The initial metering strategy was developed as part of the base build electrical and mechanical design. At this stage, the scope of metering appeared comprehensive with 90% of the energy for end use categories metered and the inclusion of heat meters for the floors. The original metering strategy included electrical meters to record power and lighting, heat meters to record LTHW and CHW energy usage, water meters and oil meters for the standby power capacity provided by the generators.
Although the strategy was already comprehensive, a review with all stakeholders was undertaken and some further meters were added to ensure all objectives were met.
Step 6: Select Appropriate Meters and Automatic Meter Reading (AMR) System
The selection of the meters centred on the use of MID approved meters as the property will be multi-occupied and therefore has a requirement for the recharging of energy costs. Additional factors considered in meter selection were:
– Meters which meet at a minimum IEC 62053-21 accuracy class 1, and CTs meeting IEC 61869-2 class 1 accuracy were selected due to the importance of high accuracy for billing; and
– Consideration was given to the registers provided by different models of electricity meters.
– In line ultrasonic type heat meters were selected due to their good levels of accuracy;
– Meters were purchased as single complete package inclusive of flow part, temperature probes and calculator to ensure that there were no issues with compatibility and correct calibration of the calculator with the other components; and
– Meters were sized according to flow rate to ensure that they record accurately as mechanical meters specify minimum and maximum flow rate thresholds within which they will operate correctly.
The AMR systems selected needed to be capable of picking up pulse outputs from the water and gas meters and Modbus protocol from the electricity and heat meters. A hard wired system was opted for to ensure reliability of communications between the meters and logging equipment. A connection was made to the internal LAN system which has a broadband link to the outside world to enable remote access and export of data. Separate onsite head-ends were provided for each of the 2 buildings which were specific to each building. A dashboard function provided the required tool for the onsite building manager to analyse and manage energy within the building on a day to day basis.
Step 7: Decide on Location of Meters
The meters on the main office floors were located within the risers for easy access. This meant the meters could be easily found in the same position on each floor and at a height which allows readings to be taken without the need for any step ladders. Additional meters located within the plant rooms and electrical switchroom were equally located in areas which are easily accessible. For mechanical meters consideration was also given to orientation to ensure that the meters were orientated at the most appropriate angle for reading them whilst complying with any installation requirements in the manufacturer’s guidelines.
Step 8: Review the Metering Strategy
The initial metering design was undertaken as part of the base build electrical and mechanical design; however, a full review was completed at design stage with input from all key stakeholders who need to use the data output post completion. Several reviews were undertaken throughout the life of the development project as illustrated in figure 1. This was important as over time modifications were made to the design which had a knock on effect on the metering requirements.
The initial review was focussed on the scope of metering in so far as the position of meters is concerned. As the project progressed it was necessary to review in more detail the type of meters to be used. The meter technical submittals were subject to analysis and approval to ensure they met the requirements which had been agreed.
Commissioning procedures put together by the base build team were also analysed to ensure that these reflected the requirements of the specific meters installed and to ensure that the building users were left with a system which delivered in practice as well as on paper.
Throughout each stage of the project, all changes and updates agreed were clearly documented with updates made to the drawings and schedules associated to the system.
Step 9: Implement and Commission the Metering
The metering was installed as part of the base build construction phase with commissioning taking place just prior to practical completion. The majority of heat meter manufacturers stipulate that flushing of water based systems during commissioning could damage heat meters. Flushing is therefore typically undertaken with spool pieces installed, which are replaced with meters once flushing is complete. This means that meters are often one of the last items to be completed and commissioned on such projects.
Independent meter commissioning checks were undertaken by Carbon2018 to verify that meters had been correctly installed and commissioned, and were in line with the specification which had been developed throughout the project. The metering had been installed to a high standard and in line with the strategy due to the high level of communication which occurred throughout the project.
Any minor issues which were identified were logged with an agreed action and timescale, and then rechecked upon completion of the required remedial work.
An ongoing programme of periodic meter verification will be undertaken to ensure the accuracy of meters is maintained.
Step 10: Document the Strategy
Full documentation relating to the metering system was drawn up for inclusion within the log book and relevant Operation and Maintenance (O&M) manuals. This included:
– A full meter schedule;
– As installed schematic drawings with meters labelled to match up to the meter schedule and AMR system;
– Floor plans indicating the physical location of the meters and data collection devices for ease of ongoing Maintenance;
– Meter data sheets and technical information; and
– Commissioning records for each meter.
The key outputs that will be derived from the system installed at 1 & 2 St James’s Market include tenant billing with full and transparent backing data for tenants, monthly energy performance dashboard indicating actual building performance against predicted, and exception reports/alarms to highlight the occurrence of anomalies and issues in order that these may be acted upon to minimise wastage.
Joanne Merry, Technical Director for Carbon2018 who acted as metering consultant on the project commented:
“Implementing a best practice approach to metering on behalf of The Crown Estate which uses the objectives to inform the strategy, incorporates all relevant stakeholders’ views and includes regular reviews/updates as required throughout the life of the project resulted in a system which met the needs of building users and other relevant stakeholders once the site was operational. “
For more information contact:
Tracy Lewis, Operations Director
telephone: 01252 878722 | email: email@example.com | website: www.carbon2018.com
view profile on ESTA at: www.estaenergy.org.uk/members/?p=457
All Carbon 2018 Limited Case Studies
- Implementing a best practice approach to metering for the Crown Estate
- 1 & 2 St James’s Market, a joint venture between The Crown Estate and Oxford Properties comprising 2 buildings, has created 210,000 sq ft of modern office accommodation, six flagship stores and seven restaurants, all set within over an acre of revitalised public spaces, including a new public square and art pavilion. | 17th October 2017