Larson Building Systems Laboratory

The Larson Building Systems Laboratory is a unique facility in the HVAC industry in that it permits the study of entire HVAC systems in a controlled dynamic environment, providing repeatable test conditions that have been heretofore unavailable. It is used for educational and research purposes and is designed for dynamic testing of complete and full-scale commercial HVAC and building systems. The facility consists of a full-size commercial HVAC system, four representative commercial building zones, a system for producing repeatable and controllable loads on the HVAC system, and sophisticated data acquisition and control systems. Activities at the laboratory include evaluation and testing of control algorithms and hardware for HVAC components and systems, interactions between multiple control functions of HVAC systems, the dynamic interactions between building thermal response and HVAC system controls, ventilation control for indoor air quality, and HVAC system diagnostics.

The laboratory testing of the full-scale thermo-active foundation will involve the use of an advanced building heating/cooling automation systems in the Larson laboratory. Johnson Controls, Inc. has provided as part of an-going project a complete building automation system including an operator workstation, a network control module, DDC control modules, and expansion devices as required by the proposed real-time optimal controller. All ancillary parts and equipment such as networking cables and support framing will be furnished. This system will allow the implementation and testing of the predictive controller in the laboratory.

Figure 1: Isometric View of the Components of the Larson Laboratory, including the heat pump system and the thermal cells (full-size zones)

The laboratory, as depicted in Figure 1, has been designed for maximum flexibility to encourage a wide variety of research and testing programs. In particular, both the HVAC and control systems in the laboratory are re-configurable in that components, subsystems or entire systems can be readily installed, tested, and modified. For this project, a thermo-active foundation will be constructed close to the Laboratory and will be used to heat and cool the full-zones which will be subjected to various thermal loading conditions.

The main HVAC system of the laboratory consists of a 12,000 cfm air-handling unit that is connected to four building zones by variable-air-volume (VAV) fan powered mixing boxes. To provide cooling to the four zones, a chiller, rated at 265 kW (75 tons) cooling capacity and comprised of two screw-type compressors, is available within the lab. Continuous capacity control is provided down to 10% of rated capacity. The chiller, a 2.2 kW (3 hp) constant-volume pump, and a 668 kWh (190 ton-hour) ice storage tank are incorporated into a primary loop. A separate constant-volume 2.2 kW (3 hp) pump circulates water through a secondary loop to the zone simulators and the two air-handling units. The chilled water loop contains a 25% glycol brine and allows the primary loop to operate at temperatures as low as -5°C (23°F).

The heating and cooling systems in the Larson laboratory are controlled using programmable direct digital control (DDC). The DDC system uses electronic actuators for damper and valve control, all of which accept standard analog control signals. The system employs laboratory-grade instrumentation for accurate control. All of the control strategies to be tested in this project can be easily programmed using this DDC system. The data acquisition can accommodate up to 300 data channels. Data collected include temperature, humidity, pressure, flow rate, fan speed, and electric power consumption. The accuracy measurements meet or exceed all relevant ASHRAE/ASTM standards.