Development of Temperature and Humidity-Based Indicators for Diagnosing Problems in Low Tonnage, Split System Air Conditioners

This paper presents results of a survey of the literature and identifies the most common degraded conditions associated with low-tonnage air conditioners. Other laboratory studies as well as marketed diagnostic systems are also summarized. A procedure for identification of useful, low-cost temperature-based indicators of degraded conditions has been developed at the Energy Systems Laboratory, Texas A&M University in College Station, TX under contract to Honeywell. This paper presents the methodology used to identify the temperature-based indicators for the most common degraded conditions gleaned from the literature

Metering and Calibration in LoanSTAR Buildings

End-use metering in commercial buildings often requires installation of a large variety of transducers and data loggers. The metering installation group in the LoanSTAR monitoring program has the primary responsibility for the installation and maintenance of the metering hardware. This paper provides an overview of the responsibilities and first year experiences of the metering installation group of the LoanSTAR monitoring program. In addition, the calibration laboratory is also described

The Effect of Reduced Evaporator Air Flow on the Performance of a Residential Central Air Conditioner

This paper discusses the measured degradation in performance of a residential air conditioning system operating under reduced evaporator air flow. Experiments were conducted using a R-22 three-ton split-type cooling system with a short-tube orifice expansion device. Results are presented here for a series of tests in which the evaporator air flow was reduced from 25 to 90% below what is normally recommended for this air conditioner. At present, very little information is available which quantifies the performance of a residential cooling system operating under degraded conditions such as reduced evaporator air flow. Degraded performance measurements can provide information which could help electric utilities evaluate the potential impact of system-wide maintenance programs

Calibration of Relative Humidity Transducers for use in the Texas LoanSTAR Program

In support of the Texas LoanSTAR Energy Conservation Program, the Texas A&M University Monitoring and Analysis Program (MAP) calibration facility has been performing relative humidity calibrations for transducers being used in field installations as well as for new units before installation. The sensors are all of the capacitive type with the element mounted on a polymer chip at the sensor probe tip. Saturated aqueous inorganic salt solutions are used as the calibration standard due to their wide use and acceptibility as a relative humidity standard. The tests are conducted through a temperature range of 0 to 44°C (32 to 111°F) and five nominal relative humidity levels of 11 %, 33%, 55%, 75%, and 83%. Early results from these tests indicate that for a given temperature, the relative humidity indicated may be significantly different than the true value. Many manufacturers claim an accuracy of ±2 to 3% over the range 0 to 100% relative humidity. Differences found during the tests for some of the transducers have been typically 10% relative humidity high at low temperatures and 10 to 15% relative humidity low at high temperatures. Accurate relative humidity measurement is important in the analysis of building energy consumption, especially in hot and humid regions where the latent cooling load is a large percentage of the total load. Clean room facilities and health care facilities also have the requirement of accurate relative humidity measurement and control

Effect of a 90° Elbow on the Accuracy of an Insertion Flowmeter, Results and Comparisons for 4 and 6 in. Diameter PVC Pipe

Thermal energy consumption in buildings with chilled or hot water distribution systems is often monitored through the use of some type of flow metering device. These flowmeters can be fixed types, such as venturis or orifices, or insertion flowmeters which can be more easily installed and removed. The easy removal and reinstallation of the insertion type flowmeters makes them good choices for use in existing buildings or in retrofit projects. Besides the installation benefits, insertion flowmeters can also be installed while the pipe is in service or ''hot tapped". With any type flowmeter however, location in the pipe is a critical problem and deserves special consideration. Ideally, the meter should be inserted in existing pipe with a minimum of 10 to 15 diameters of straight pipe upstream of the meter location. This is rarely the case in existing piping distribution systems. It is much more common to be faced with only one or two candidate metering locations and these often are very short straight runs or will have elbows upstream and downstream of the proposed metering location. This paper reports on flow measurement error resulting from an insertion flowmeter installed downstream of a 90° elbow. The measurement errors were compared for tests conducted in 4.0 and 6.0 inch (0.1 and 0.15 meter) diameter PVC pipe. The insertion flowmeter was a nonmagnetic, tangential paddle wheel type. The flowmeter was located from 2 to 10 pipe diameters downstream fiom a 90° elbow with fluid velocities ranging from 1.0 to 10.0 ft/s (0.3 to 3.0 m/s). At each flowmeter location, the meter was rotated in 45° increments around the circumference of the pipe to quantify the effect of circumferential location on flow error. The flowmeters were tested at the energy metering calibration facility at the Texas A&M University Energy Systems Laboratory Riverside campus. Flowmeter output was compared to mass flow measurements obtained 6om precision load cells mounted beneath a 1342 ft^3 (38 m^3 ) weigh tank. All output is given in terms of percent error relative to the load cells. Final results are presented as a bction of flowmeter downstream location, circumferential rotation angle, and fluid velocity. Circumferential meter location was found to be a very important factor. The percent difference for the tested flow meters ranged 6om -23% to -5% in the 4.0 in. (0.1 m) pipe and 6om -33% to 1% in the 6.0 in. (0.15 m) pipe. The ''best" location for these flowmeters was at zero degrees rotation angle, regardless of pipe size or meter location relative to the upstream 90° elbow

Program Overview: The Texas LoanSTAR Program; 1989-October 1999, A 10-Year Experience

The Texas LoanSTAR (Loans to Save Taxes and Resources) program was conceived as a $98.6 million capital retrofit program for building energy efficiency. The funding source is petroleum violation escrow funds (PVE) from the Federal government. LoanSTAR is administered by the Texas State Energy Conservation Office of the Comptroller's Office, under the guidance of Dub Taylor, Director, and is the largest revolving loan fund administered by a state for conservation purposes. LoanSTAR was conceived in 1988 and began in 1989. This paper summarizes the program dollar savings and environmental impact from its inception through October 1999

Instrumenting Buildings to Determine Retrofit Savings: Murphy's Law Strikes Again

Experiences with instrumentation, installation and maintenance of building energy metering systems are presented. The building energy metering was installed in a variety of locations in programs handled by the Energy Systems Laboratory at Texas A&M University. Metering typically includes monitoring for the whole-building electric load, chilled and hot water thermal loads and selected submetered electrical loads. The emphasis of the lessons learned was on the instrumentation used and installation and maintenance problems encountered during the course of the metering projects

A cool starspot or a second transiting planet in the TrES-1 system?

We investigate the origin of a flux increase found during a transit of TrES-1, observed with the HST. This feature in the HST light curve cannot be attributed to noise and is supposedly a dark area on the stellar surface of the host star eclipsed by TrES-1 during its transit. We investigate the likeliness of two possible hypothesis for its origin: A starspot or a second transiting planet. We made use of several transit observations of TrES-1 from space with the HST and from ground with the IAC-80 telescope. On the basis of these observations we did a statistical study of flux variations in each of the observed events, to investigate if similar flux increases are present in other parts of the data set. The HST observation presents a single clear flux rise during a transit whereas the ground observations led to the detection of two such events but with low significance. In the case of having observed a starspot in the HST data, assuming a central impact between the spot and TrES-1, we would obtain a lower limit for the spot radius of 42000 km. For this radius the spot temperature would be 4690 K, 560 K lower then the stellar surface of 5250 K. For a putative second transiting planet we can set a lower limit for its radius at 0.37 R$_J$ and for periods of less than 10.5 days, we can set an upper limit at 0.72 R$_J$. Assuming a conventional interpretation, then this HST observation constitutes the detection of a starspot. Alternatively, this flux rise might also be caused by an additional transiting planet. The true nature of the origin can be revealed if a wavelength dependency of the flux rise can be shown or discarded with a higher certainty. Additionally, the presence of a second planet can also be detected by radial velocity measurements.Comment: 8 pages, 6 figures, accepted for publication in A&

A Simplified Procedure for Sizing Vertical Ground Coupled Heat Pump Heat Exchangers for Residences in Texas

A simplified technique for the sizing of vertical U-tube ground coupled heat pump (GCHP) heat exchangers for Texas climates was developed utilizing a transient simulation model of a ground coupled heat pump and weather and soil data for Texas. The simulation model discretized the ground heat exchanger into elements and computed the temperature distribution surrounding the heat exchanger on a minute-by-minute basis. Hundreds of runs were made with the model for a wide range of ground temperatures, ground thermal properties (density, thermal conductivity, and specific heat), and outdoor weather. A set of sizing charts were developed from the model runs that could provide quick reference on the size of the ground heat exchanger. Corrections for ground temperature, ground density, ground thermal conductivity, and indoor air temperature were presented. Soil temperature and thermal conductivity were found to be the most important parameters for sizing GCHP heat exchangers. Results from the simplified method were compared to two available heat exchanger sizing methods: the National Water Well Association (NWWA) and the International Ground Source Heat Pump Association (IGSHPA). The simplified method predicted shorter lengths than those from either of these two methods

Monitoring the Performance of a Residential Central Air Conditioner under Degraded Conditions on a Test Bench

This report presents the measured degradation in performance of a residential air conditioning system operating under degraded conditions. Experiments were conducted using a R-22 threeton split-type cooling system with a short-tube orifice expansion device. Results are presented here for a series of tests in which the various commonly occurring degraded conditions were simulated on a test bench. At present, very little information is available which quantifies the performance of a residential cooling system operating under degraded conditions. Degraded performance measurements can provide information which could help electric utilities evaluate the potential impact of systemwide maintenance programs. This report also discuss the development of a diagnostic procedure based on measurement of refrigerant and air side temperatures