World Library  
Flag as Inappropriate
Email this Article

HVAC control system

Article Id: WHEBN0000396508
Reproduction Date:

Title: HVAC control system  
Author: World Heritage Encyclopedia
Language: English
Subject: Help desk/Archives/2015 March 10, Building automation, Compressed air, Air compressor, Crestron Electronics
Collection: Building Automation, Heating, Ventilating, and Air Conditioning
Publisher: World Heritage Encyclopedia
Publication
Date:
 

HVAC control system

HVAC (stands for Heating, Ventilation and Air Conditioning) equipment needs a control system to regulate the operation of a heating and/or air conditioning system. Usually a sensing device is used to compare the actual state (e.g. temperature) with a target state. Then the control system draws a conclusion what action has to be taken (e.g. start the blower).

Contents

  • Direct digital control 1
  • Building Automation System 2
  • History 3
  • See also 4
  • References 5

Direct digital control

Central controllers and most terminal unit controllers are programmable, meaning the direct digital control program code may be customized for the intended use. The program features include time schedules, setpoints, controllers, logic, timers, trend logs, and alarms. The unit controllers typically have analog and digital inputs that allow measurement of the variable (temperature, humidity, or pressure) and analog and digital outputs for control of the transport medium (hot/cold water and/or steam). Digital inputs are typically (dry) contacts from a control device, and analog inputs are typically a voltage or current measurement from a variable (temperature, humidity, velocity, or pressure) sensing device. Digital outputs are typically relay contacts used to start and stop equipment, and analog outputs are typically voltage or current signals to control the movement of the medium (air/water/steam) control devices such as valves, dampers, and motors.

Groups of DDC controllers, networked or not, form a layer of system themselves. This "subsystem" is vital to the performance and basic operation of the overall HVAC system. The DDC system is the "brain" of the HVAC system. It dictates the position of every damper and valve in a system. It determines which fans, pumps, and chiller run and at what speed or capacity. With this configurable intelligency in this "brain", we are moving to the concept of building automation.[1]

Building Automation System

More complex HVAC systems can interface to Building Automation System (BAS) to allow the building owners to have more control over the heating or cooling units. The building owner can monitor the system and respond to alarms generated by the system from local or remote locations. The system can be scheduled for occupancy or the configuration can be changed from the BAS. Sometimes the BAS is directly controlling the HVAC components. Depending on the BAS different interfaces can be used.[2]

Today, there are also dedicated gateways that connect advanced VRV / VRF and Split HVAC Systems with Home Automation and BMS (Building Management Systems) controllers for centralized control and monitoring, obviating the need to purchase more complex and expensive HVAC systems. In addition, such gateway solutions are capable of providing remote control operation of all HVAC indoor units over the internet incorporating a simple and friendly user interface.[3]

History

It was natural that the first HVAC controllers would be pneumatic since engineers understood fluid control. Thus, mechanical engineers could use their experience with the properties of steam and air to control the flow of heated or cooled air.

After the control of air flow and temperature was standardized, the use of electromechanical relays in ladder logic to switch dampers became standardized. Eventually, the relays became electronic switches, as transistors eventually could handle greater current loads. By 1985, pneumatic controls could no longer compete with this new technology although pneumatic control systems (sometimes decades old) are still common in many older buildings.[4]

By the year 2000, computerized controllers were common. Today, some of these controllers can even be accessed by web browsers, which need no longer be in the same building as the HVAC equipment. This allows some economies of scale, as a single operations center can easily monitor multiple buildings.

See also

References

  1. ^ Role on DDC Systems in Building Commissioning
  2. ^ KMC Controls. "Understanding Building Automation and Control Systems". Retrieved 22 April 2013. 
  3. ^ "CEDIA Find: Cool Automation Integrates Smart Air Conditioners with Third-Party Control Systems". CEPro. Retrieved 16 Jun 2015. 
  4. ^ KMC Controls. "Pneumatic to Digital: Open System Conversions" (PDF). Retrieved 5 October 2015. 
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.