Configuring an HVAC System using National lnstruments Products

A Heating, Ventilating and Cooling system is the primary element in controlling environmental temperatures of an enclosed area; whether it be a warehouse building, a test chamber or commercial vehicle. The HVAC system will also provide fresh outdoor air to the enclosed area to dilute any contaminants in the air and to increase circulation. HVAC systems will control and adjust temperatures to improve comfort and increase efficiency. By performing tests on the HVAC system and improving the control, you will be able to optimize the performance of the system, provide the highest level of environmental comfort and increase energy efficiency.

There are several benefits associated with building a test and control unit for your HVAC system. First and foremost, the objective is to create an optimal working environment. If the HVAC system is to be used to control the environment of an office building, you want to ensure that the workers are comfortable at all times of the day. An optimized HVAC system will properly control temperature, reduce humidity, and circular air throughout the building.

HVAC systems make up approximately 50% of energy usage in commercial and residential buildings. By testing the HVAC system, you will be able to determine if there are inefficient areas of the environment. Possible areas where the heating is lost or the cooling does not reach an important area, thus causing the system to work harder to meet desired setpoints. Being able to test your system, you can create custom controls that will increase reliability and performance of your system therefore making it more energy efficient.

A Typical HVAC System

The HVAC system consists of some sort of heating system such as boilers, furnaces or electric heat; a cooling system such as air conditioning or chillers; and ventilation components. In order to analyze and control the system, several elements of the environment need to be tested:
· Temperature
· Relative Humidity
· Pressure
· Air Flow
· Speed

To control the HVAC system, analysis needs to be performed on the testing results from each of these elements. Utilizing a control algorithm, adjustments can be made to the heating, cooling and ventilation components in order to meet the user-specified setpoints. This adjustments process will continue in a closed-loop feedback process.

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Oftentimes, simulation can be done on this closed-loop control system beforehand to predict the “ideal” behavior of the system. Mathematical models can be used to accurately represent the real world hardware and produce its expected response to environmental conditions. By performing simulation ahead of time, you could reduce the development and testing time of the actual control hardware and easily optimize your system. Simulation can also be helpful after setting up the system to assist in making adjustments to the control algorithm.

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Benefits of National Instruments Control System

Using National Instruments’ products, you can easily decrease the development time of a control and test system for your HVAC components while ensuring that you can monitor and adjust your system for future improvements. National Instruments’ tight integration between software and hardware provide many benefits to an HVAC testing system such as:

· Distributed Hardware platforms for industrial, high channel count and mixed I/O testing
· Signal Conditioning for improved measurements
· Software integration for ease of programming
· Real-Time environment for reliability and determinism
· Ethernet communications for easy user access and inter-communication
· Distributed User Interfaces
· Data Logging for Trends
· Simulation to provide a H-I-L type application
· Remote access to setup
· Ability to easily upgrade for future expansion

Software

Package	Description
NI Developer Suite Professional Control Edition (776678-09)	With LabVIEW, you can rapidly create automation applications using intuitive graphical development. LabVIEW integrates measurements, vision, and motion into one platform. The Professional Control Edition includes the LabVIEW Real-Time and LabVIEW Data Logging and Supervisory Control modules.
LabVIEW Real-Time (777844-03)	LabVIEW Real-Time and RT Series hardware deliver deterministic, real-time control needed for machine monitoring and test systems. You can choose LabVIEW RT Series hardware targets based on PXI and FieldPoint depending on the performance and I/O requirements of your industrial machine monitoring and control system.
LabVIEW Data Logging and Supervisory Control (778311-03)	LabVIEW Data Logging and Supervisory Control offers data management tools, such as easy-to-use I/O configuration for large-channel-count applications, automatic data logging, full alarm management and event logging, and real-time and historical trending. With easy networking, including a networked database for distributed logging, built-in security, and OLE for process control (OPC) connectivity, the LabVIEW Data Logging and Supervisory Control Module provides tremendous ease of use to get your high-channel-count system up and running quickly.
LabVIEW Simulation Interface Toolkit (778552-03)	The National Instruments LabVIEW Simulation Interface Toolkit gives control system design and test engineers a seamless link between LabVIEW and The MathWorks Simulink® software. With these integrated tools, engineers can build custom LabVIEW user interfaces to interactively view and control data in the Simulink environment. By extending your Simulink simulation software with LabVIEW, you can import the model into LabVIEW to integrate with real-time hardware I/O. With these capabilities, you can take a control model from software verification to real-world prototyping and hardware-in-the-loop simulation.
MATRIXx (www.ni.com/matrixx)	Engineers worldwide rely on the high-performance MATRIXx product family for system design projects in automotive, aerospace/defense, process control, and academic environments. With the MATRIXx software suite - Xmath, SystemBuild, AutoCode, and DocumentIt - you gain a complete solution for mathematical analysis, dynamic modeling and simulation, automatic code generation, and automatic documentation generation.

Hardware Configuration

Function	Task or Measurement	Solution	Product
Real-Time HVAC Control and Testing Remote Controller	N/A	Real-Time Control Datalogging Display Communications	NI PXI-8186/2.2 RT (778468-33) cFP-20x0 RT (777317-20x0)
Testing of Environmental Conditions	Temperature	Analog Input with Scaling and Amplification	NI SCXI-1102B (776572-02B) cFP-TC-120 (777318-120)
	Relative Humidity Air Flow	Analog Input with Scaling	NI SCXI-1102C (776572-02C) cFP-AI-110 (777318-110)
	Pressure	Analog Output with Amplification	NI SCXI-1124 (776572-24 ) cFP-AO-200 (777318-200)
Control of HVAC System	Heating and Cooling control	Digital Output and Switching	NI PXI-6627 (777802-01) cFP-DO-401 (777318-401)

Reader Comments | Submit a comment »

Cost and Application
Dear Sirs, This is a very interesting subject that requires more information: How NI system compares with the regular controls included in the HVAC units. What is the cost of all the hardware and software required for a typical system
- ewp@ispnook.com - Feb 21, 2004