Sunday, January 29, 2017: 11:00 AM-12:30 PM
Building Operation and Performance
Chair:
David P. Yuill, Ph.D., P.E., University of Nebraska
Technical Committee: 8.11 Unitary and Room Air Conditioners and Heat Pumps
Sponsor: TC 7.5 Smart Building Systems
CoSponsor: 7.3 Operation and Maintenance Management
Faults happen. They can occur in unitary air-conditioning equipment and cause it to perform below its expected, rated or designed value, leaving owners/operators disappointed. Examples of faults include coil fouling, loss of refrigerant charge, excessive duct flow resistance, economizer faults, etc. This seminar shows results of recent groundbreaking research projects focusing on the effects of faults on unitary equipment, and presents new methods for modeling the effects of those faults. Attendees of the seminar will be prepared to account for these effects when designing, planning maintenance, or predicting building energy performance.
1 Effect of Heat Pump Commissioning Faults on Annual Energy Use
This study shows the impact of common commissioning faults on the energy consumption of an air-to-air heat pump installed in a single-family house. Through annual simulations of the house/heat pump system, the study found that duct leakage, refrigerant undercharge, oversized heat pump with nominal ductwork, low indoor airflow due to undersized ductwork, and refrigerant overcharge have the most potential for causing significant performance degradation and increased annual energy consumption. Energy use increased significantly from lowering the thermostat setting in the cooling mode to improve indoor comfort in cases of excessive indoor humidity levels due to installation faults.
2 Modeling the Effect of Vapor Compression Cycle Faults Using Gray-Box Models
Complete physics-based models of vapor-compression refrigeration equipment can be difficult and time-consuming to produce. A gray-box model uses a mix of physics and measurement data to simplify the modeling process. Gray box models have recently been produced that are capable of accurately modeling the effects of all common faults on the performance of the system. This seminar describes the new approach, and show the results and conclusions from the modeling.
3 Effect of Economizer Faults on Expected Whole-Building Energy Savings
Air-side economizers are commonly used in most locations to reduce the cooling load when outdoor conditions are suitable. However, several field studies have shown that economizer faults, such as a stuck damper, are quite common. For small rooftop units, the cost of supplying an economizer can return a slow payback in some locations, and when faults occur, the economizer may not ever pay off. This study simulated the cost outcome using probabilities of faults from field studies to examine the cost-effectiveness of economizers for typical buildings in several climates, to determine payback period, if any.
4 Generalized Models of Fault Effects on Air Conditioners in Heating and Cooling Mode
Air-side economizers are commonly used in most locations to reduce the cooling load when outdoor conditions are suitable. However, several field studies have shown that economizer faults, such as a stuck damper, are quite common. For small rooftop units, the cost of supplying an economizer can return a slow payback in some locations, and when faults occur, the economizer may not ever pay off. This study simulated the cost outcome using probabilities of faults from field studies to examine the cost-effectiveness of economizers for typical buildings in several climates, to determine payback period, if any.