July 2009


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6 Useful Tips for Smart Meters and Plug Loads
As buildings move to incorporate more sensors and metering to generate data about usage and performance, metering and monitoring the electrical distribution and plug load will be integral.


Jim Sinopoli PE, RCDD, LEED AP
Managing Principal,
Smart Buildings

Contributing Editor

“We believe that electricity exists, because the electric company keeps sending us bills for it, but we cannot figure out how it travels inside wires.”
Dave Barry, American Writer and Humorist

In the vast majority of buildings there is a lack of data on how the facility and spaces within it are performing. Without measuring the attributes of the building we can’t properly manage the building. Electrical metering is one way to measure and obtain data to manage the electrical load. Smart power strips are another method to monitor and manage dense electrical plug loads. Finally, Power over Ethernet (PoE) management software is a tool to address low-voltage power to IT, telecom and security devices. These three solutions cover a substantial portion of the electrical load and allow a building owner to identify the power being provided to the building, and tenants and spaces within a building. Such data is the foundation of actionable information that can be used to minimize the major cost directly affecting the operating expenses and the overall value of the building. These solutions can also be used to pinpoint problems and to maintain occupant and user satisfaction.

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Electric Meters
Metering and meter reading is a well developed field for utilities but the experience has been with legacy metering systems. The legacy systems are static in how often data is gathered, limited in what can be monitored and only provide one-way communication. For example, older meters can provide information on how much electricity was used but cannot tell you when it was consumed. Smart meters gather data in real-time or near real time and can provide not just usage data but information on outages, malfunction, quality, etc. They may also have the intelligence to react to demand response, the key communications between the building and the electrical grid which allows the building to react to different prices for energy consumption based on the time of day and the season.

There are generally two types of power meters for buildings. One is for monitoring and measuring power to the whole building. The others are submeters, meant to measure usage for specific spaces, tenants or electrical circuits, primarily to allocate or bill-back the cost of electric power to those who consumed it.

The submeters typically have a couple components to their deployment. One is a current transformer or “CT”. The CTs are monitoring devices that look like a donut and lock on to individual electrical circuits at an electrical panel. The CT senses and gathers data on voltage, wattage and amperage on the circuit in real-time or near real-time. Multiple CTs will connect to a processor or a server/controller, with the processor having a connection to an IP or BAS control network. Typical communications protocols are Modbus TCP, SNMP MIB over an Ethernet connection, Modbus RTU over an RS-232 connection and BACnet over an RS-485 network. Submeters are generally meant to provide information on energy consumption based on kilowatt hours (kWh).

The monitoring of critical equipment, such as switchboards and switchgear is much more sophisticated than submeters, gathering data on a wide range of electrical characteristics to monitor the quality of the power and provide diagnostics.

Electric MetersMetering and submetering allows customers to make changes in their operation to reduce energy consumption. For example, if the data provided by a meter shows that a large electric load exists when a building is unoccupied there may be equipment running that needs to be shut off. The data may also show that shifting certain equipment schedules will reduce charges from the utility companies by eliminating demands during peak periods. Energy use indices (EUIs), such as kilowatt-hours used per square foot (kWh/ SF), can be compared between similar buildings to determine if a building is using more energy than it should. EUIs can also be compared to previous data to see if the building’s energy usage has increased. Since equipment efficiency tends to decrease over time, observations in energy usage can indicate when equipment is in need of service or replacement.

A power management software application will turn the metering data into actionable information in order to provide trending data, bill-back capabilities, and identify sources of peak demand charges and power quality problems. Firms such as Triacta will remotely read the meters and provide the owner or facility manager web-based access to energy cost tracking tools and relevant data, thus eliminating procuring and maintaining hardware and software.

Smart Power Strips
Standby power or “vampire power” is electrical power consumed from electronic devices turned off or in standby mode. Studies in the USA, Britain, France, Netherlands, Australia and Japan show the consumption of electrical power due to standby power between 7-13%. The US Department of Energy has stated that in the average home, 75% of the electricity used to power home electronics is consumed while the products are turned off.

Smart Power StripsWe’re talking everything from printers to cell phone chargers to DVD players to copiers to televisions to fax machines. It tends to be concentrated in areas such as offices and media centers. For example, the typical desk at one’s office, whether at work or at home has a personal computer, a monitor, maybe a printer, a scanner, a VoIP telephone, a recharger for a cell phone, etc. In the past the only management choice was to unplug the devices, a move that may be unpractical and unsafe.

Typically these devices are fed by a power strip with some surge protection. Now the typical power strips have gotten smarter by incorporating microprocessors, thus allowing the strip to sense the electrical current and to monitor and manage the plug load. Some outlets on the power strip may be able to turn devices on or off by sensing whether the device is in use or in a prolonged idle state. The outlets can be turned off within a user-defined set time after the device goes idle. Other power strips are triggered by the personal computer; that is the personal computer is plugged into a “control plug” on the power strip and the power strip will shut down the peripheral devices when the personal computer is shut down.

Smart power strips can incorporate meters to provide information to users regarding energy consumption. Some go as far as providing energy costs, and power quality including voltage, line frequency, and power factor.

The smart power strips have also moved into data centers where rack-mounted power strips feed servers, network switches and other equipment. These power strips have an IP Ethernet port allowing managers to monitor, manage and reboot equipment intelligently.

The Other Plug Load PoE
PoE is probably the most under-valued technology in buildings. It not only moves devices from high to low voltage and provides both power and communications through one cable, but it can centrally monitor the devices. The devices can be telephones, wireless access points, cameras, paging speakers, card readers, etc. Several major IT manufacturers have developed software to manage the power to the devices, either turning the devices off and on, or, in the case of Nortel “dimming” the power to the device, much like a lighting control systems.

Control Solutions, Inc The PoE management software essentially enables and disables power-over-Ethernet (PoE) ports on a network switch. The result is a reduction in peak energy demand for IT networks and the flexibility for network managers to set different power consumption for various IT devices. The PoE management software is typically a module in a larger suite of network management tools with capabilities to scale from one network to an enterprise. Since the devices that are monitored and managed are already on an IT network, the monitoring of the devices is done with SNMP tools to evaluate any device defined by a Management Information Base (MIB).

Metering Tips
As buildings move to incorporate more sensors and metering to generate data about usage and performance, metering and monitoring the electrical distribution and plug load will be integral. So what are some tips to start? Here are a few:

1. Plan and Test
Map out the areas or equipment to be submetered and record these on electrical drawings. See if you can match up power consumption to specific work tasks or departments. Target a couple of building spaces where you think consumption may be excessive. Use the spaces as test beds before a full scale deployment.

2. Include 3-phase HVAC Loads and In-Building Distribution Transformers
Monitoring the energy consumption or start-up of some of the HVAC components will help in identifying and addressing potential problems prior to equipment failure and excessive repair costs. Monitoring in-building distribution transformers will give you an idea of how close they are operating to capacity.

3. Check The Installation Of The CTs
The most common mistakes during installation are reversed CTs (installing it backwards) or placing the CT's on the wrong circuit, thus monitoring the wrong load. Use a licensed electrician for installation.

4. Get Granular
If you install smart power strips, go for the high value targets. For example, the cost of standby power for a plasma display is 5 times that of a PC - 13 times that of a printer – so you will want to tackle the plasma first.

5. Get Real As In Real Time Data
You do not want to wait a couple days before finding out there’s a problem needing repair or consuming excessive power. Real time data is a must in identifying potential problems early and avoiding peak demand charges. Connect the meters to your BAS system via BACnet or Modbus, and also provide for connectivity and access via the web.

6. Check The Business Aspects
See if rebates or tax incentives are available from you utility or a government entity to help fund the effort.

For more information about smart buildings, technology design or to schedule a Continuing Education program, email me at jsinopoli@smart-buildings.com.


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