Common Metering Challenges

Challenges can occur in planning, specifying, purchasing, installing, or in the maintaining of an advanced metering infrastructure system. This best practice focuses on some of the more common metering challenges with the hope that identifying these early in the process mitigates potential impact.

Metering Planning. The planning step of the metering process is critical to program success. Some of the challenges in the planning process include:

  • Best Information. Good information drives good planning and decision-making. It is incumbent on the planners to make sure the best available information is accessed and used. In metering of existing buildings, access to electrical plans, one-line diagrams, and panel schedules is critical. However, these documents (when available) are often incomplete, outdated, or are not considered “as-built.” A recommended step in the planning process is the access and verification (possibly confirming with field inspection and spot measurement) of all technical documents.
  • Under/Overestimating Breadth of Project. A key to metering planning resides with an ability to estimate current and future needs. While it is difficult to accurately predict future needs, efforts to plan for future system expansion are critical to the economic success of the system. This is often done by scenario phase-planning whereby different project implementation assumptions are used to create best, most likely, and worst-case scenarios. These different scenarios are then factored into the planning process.
  • Management Buy-in and Support. Obtaining and maintaining management support for project planning and implementation is an often overlooked activity. Providing management with regular updates on activities and successes is one way to keep the project visible and maintaining this support.
  • Milestone Development. While many plans focus on the “what,” effective plans also focus on the “how.” Developing how and when the steps of the process will be implemented are critical to assuring a successful metering program.

Equipment Specification. Identifying the correct equipment is crucial to the project’s success and longevity. This requires an ability to distinguish the necessary parameters for proper function.

  • Operating range. When selecting metering equipment, understand the operating range of the expected measurements. Metering equipment capacity should be sized based on the expected operating range and never based on pipe size or circuit capacity
  • Accuracy. As defined, the accuracy of a metering system is the difference between the measured value and the actual value. While overall system accuracy is important and often reported for standard operating ranges, accuracy should be addressed for each component of the system and, importantly, over the entire range of expected values. Current transformers (CTs) and fluid meters present good examples of this need.
    • CTs are usually accurate over a broad range. Basic CTs provide high accuracy from 10 –  110 percent of the rated current. Higher quality CTs, however, can provide high accuracy from 1 – 120 percent of the rated current. CT sizing should be done with care and full knowledge of the expected measurement range, paying particular attention to the low end of the range.
    • Fluid meters are often specified on average and maximum flow rates. In systems with a wide range, including low-flow rates, accuracy can suffer. In these cases, compound meters can be deployed to accommodate the two different flow rate regimes to achieve desired accuracy.
  • Operation. Prior to procurement, it is important to understand the function, operation, and maintenance needs of the advanced meter. This step must involve input from users of the equipment. Parameters to consider include:
    • Meter installation and setup, paying particular attention to spatial constraints and code requirements
    • Flow meters may require strainers or filters, straight pipe runs or flow conditioners, and isolation valves for ease of maintenance.
    • Software configuration and ease of use
    • Process and schedules for maintenance of system, sensors, and battery needs
    • Data synchronization for various meters and data acquisition systems
  • Communications. Meters from different vendors or product lines can have different data sampling rates, sampling intervals, and communicate and transmit data using different protocols and formats (ACEEE 2020). To mitigate any potential issues with communication, consider the following guidance:
    • Standardization on manufacturer and/or data protocols. There are many established and developing protocols (e.g., BACnet, LonWorks, Modbus, pulse);  specified meters should have a common protocol or the ability to be converted for proper communication.
    • Data collection intervals. To assure accurate data processing, meters should be set to a universal time stamp (i.e., time-series records reference the same time stamp) and collecting and integrating over the same interval (e.g., a 15-minute interval).
    • Data interoperability. Depending on how data are collected and processed, routines may need to be employed that pre-condition or consolidate the data for final processing.
    • Cost of ownership. An important metric in specification is total cost of ownership over the equipment’s life. Identifying the defined life of the system is the first step. It is important to determine the recurring cost, including any periodic calibration, needs for part/sensor replacement, or upgrades to system software or licensing. All parameters should be readily available from equipment vendors and should be received in writing. Most importantly, facility managers should weigh the real benefit of additional features and options and should not “over buy” metering equipment by adding features and options that add costs without corresponding potential savings.

Contracting and Purchasing. The details and specifications of items procured are very important when purchasing metering equipment and accompanying sensors. Procurement specifications should be developed with engineering and facilities management input/oversight and include a thorough review before any purchase orders are signed.

  • Manufacturer Standardization. While it is not always possible, there are some advantages to standardizing on one equipment manufacturer; these include:
    Single source of information and product
    • Minimization of finger pointing when system problems occur
    • Volume procurement/discount opportunities

Installation. Following all manufacturers’ guidelines and relevant code requirements is essential to proper and safe installation. Additional recommendations to consider include the following:

  • Offer an explicit instruction set for all installations, provide relevant contacts for installation questions, and develop checklists for installation check out. Typical installation faults include:
    • CT directionality or flow direction
    • Voltage and phase consistency
    • Meter constants, inputs, and programming
    • Maximum output signal communication distances
    • Meter power supply
  • Develop installation commissioning protocols. Verify each meter individually.
    • Develop expected values for each meter.
    • Compare output against expected values and spot measurements.
    • In multi-meter installations, verify that the sum of the parts equals the whole.
    • Individual end use, distribution centers, and building-level
  • Develop communication commissioning protocols.
    • Verify each meter individually.
    • Confirm time series output received at endpoint/data center.
    • Confirm summed data received over duration (week/month) are accurate and expected.

Maintenance. Once installed and operating, facility staff must focus on keeping metering systems productively functional. Meter/sensor calibration, data receipt, and accuracy are the key meter maintenance parameters most often neglected. To prevent these issues from arising, the following are suggested:

  • Consider developing time-based checklists of manufacturers’ maintenance recommendations and include these in regular maintenance activities.
  • If the site uses a computerized maintenance management system, all relevant metering information (manufacturer, model, date of installation, size, and procedures) should be entered into the computerized maintenance management system from where automated work orders will be generated.