OnsetHobo UX90-004M Temperature Logger for Feasibility Improvement of Demand Side Management Projects

In any demand side management (DSM) or energy saving project, the first step is to identify potential energy saving measures and assess what level of savings might exist. These expected savings are often based on how we think the building will work. But utilities don't pay incentives based on expectations; they pay results-based incentives.

For example, a company might estimate lighting savings of $2,500 per year based on expected hours of operation. Available annual savings of $6,000 can be based on actual operating hours. Differences between expected and actual times may be attributable to factors such as burning lights at night for cleaning crews, modifying operating schedules based on business activity, or a lack of understanding of how the building operates.

When utilities provide programs, they encourage energy efficiency, not new equipment. They want to verify savings claims. Utilities make investments in their customers' facilities and need to confirm that the investments are justified.

Portable data loggers are one of the many tools we use in DSM projects to understand building energy efficiency and demonstrate efficiency requirements. Energy saving and measurement and verification professionals, we enter the facility, deploy data loggers on selected equipment, and perform calculations based on the data collected. This information is used to evaluate program performance and to indicate what incentives clients are eligible for.

In the same way that utilities verify customer claims, state governments monitor utility company programs to ensure their programs are effective. This is necessary because most utility incentive programs are funded from local tax payer dollars. Data loggers provide credibility to DSM projects, and they do so in an independent and unbiased manner.

In one project, we installed temperature loggers with occupancy sensors in hotels, air conditioners and heat pumps to reduce operating hours. We employ a logger that measures efficiency improvements and demonstrates a reduction in runtime.

Our first step was to develop a monitoring program using data loggers for room temperature and AC system compressors while running UX90-001, UX90-001M, UX90-004, UX90-004M, UX120-017, UX120-017M. We deployed these loggers throughout the hotel, collected data for two weeks, then offloaded and analyzed the data.

Ultimately, we found no noticeable operational differences in hotel rooms equipped with new thermostats and occupancy sensors, compared to standard guest rooms. Thermostats and occupancy sensors promise to reduce energy use, but in this case, we couldn't find any evidence of savings. In turn, this is an indication that the new thermostat is not properly commissioned - the timeouts and sensitivities of the thermostat have been overridden, and even if there is no energy saving is not what the customer wants to hear, it is information they can act on. Without this information, customers and utilities will assume that new controls save energy only because they are expected.

When evaluating HVAC systems, we often look at rooftop unit upgrades. Questions we asked included what is the air conditioning load and how does it relate to the outside temperature? In these cases, we used data loggers to track energy consumption in packaged units as a function of temperature. This gives us the relationship between temperature and energy savings used, and allows us to make reliable estimates. From this information, we can usually project savings in energy use and a full year based on observations of only a few weeks.

Systems commissioned in buildings are often part of a DSM project. This is the operating system of tuning architectural practices, so they function. While many facilities have energy management systems (ems) in place to control heating and cooling equipment, calibrated sensors and actuators often fall out. Therefore, you cannot use the EMS to verify itself; you need an independent verification method for the accuracy and operation of the EMS system.

During our system commissioning work, we often see economizer problems. For example, if the damper actuator is open when it should be closed, the building may be drawing in outside air at 90 degrees outside at 100%. This unnecessarily increases cooling load and energy usage. We usually deploy temperature loggers, such as Onset's HOBO series U12 series loggers, to measure outdoor air, return air, and mixed air temperatures. These U12 series loggers are set every 15 minutes for one or two weeks. We use these data to calculate the economizer performance by observing the ratio between the temperature differences. This is a relatively easy way to observe the economizer behavior for control and diagnosis of control or actuator problems.

While building energy simulation models can improve building design, the information gathered by data loggers can help improve building operations. In these difficult economic circumstances, building managers and operators are paying more attention to how their buildings are performing, and are investigating HVAC performance, supply and return air temperatures, light usage patterns, and engine and pump run times. Improving building performance and reducing operating costs requires identifying the difference between how a building is expected to function, and how it operates. Data loggers provide hard evidence to make informed decisions.