Air Handlers and their Components

This article will discuss the various components of air handlers as related to larger heating, ventilating, and air-conditioning (HVAC) systems in most commercial buildings. Generally an air handler cabinet, which is a large metal box, contains a blower, heating and/or cooling elements, filter racks/chambers, sound attenuators, and dampers (a larger air handler that conditions 100% outside air, and no recirculated air, is known as a makeup air unit). Air handlers connect to ducts that distribute the air through the building.

The general components included in an HVAC system are:

• Blower/fan
  
• Heating and/or cooling elements
  
• Filters
  
• Mixing chamber
  
• Controls
  
• Vibration isolators
  
  

Fans/blowers - Air handlers typically use a fan or blower (or several fans or blowers) to move the air. The blower can operate at variable speeds and flow rates.

Heating and cooling elements - Most large air handling units utilize coils to circulate hot water for heating and cold water for cooling. The hot water is provided by a boiler, and the chilled water is provided by a chiller.

Controls - Controls regulate the normal functions of an air handler. They monitor rate of flow, supply temperature, mixed air temperature, humidity, and quality. Most control components contain temperature sensors, humidity sensors, sail switches, actuators, motors, and controllers.

Vibration isolators – The large fans required in commercial buildings can often lead to substantial vibration. Vibration isolators prevent this vibration from being transferred to the buildings occupants by absorbing the vibrations from the fan/blower.

An Overview of Building Automation

The term Building automation refers to an intelligent network of programmable controllers and software that monitors and controls mechanical heating, ventilation and air conditioning equipment, and indoor and outdoor lighting in a building. The primary function of a building automation system or energy management system is to increase the efficiency of a building and reduces energy and maintenance costs.

Building Automation systems optimize the performance and maintenance of multiple building control systems including;

• Heating, ventilation, and air conditioning (HVAC) – These systems include central plants, air handling units, package units and fan coils.
  
• Lighting systems – including indoor and outdoor systems.
  
• Metering systems – including electrical meters, gas meters and BTU meters.

There are two major components to building automation systems; the user interface software and the controller. The user interface is typically a computer based graphical software application that allows the user to interface with the system and provides the user full control over the building automation system.

A controller is an electronic device that monitors and changes the operations of a specific system. The operational conditions include output variables of the system which can be affected by adjusting certain inputs. For example, an HVAC system in a commercial building can be equipped with a controller for sensing air temperature (output variable) which can turn on or off a heater when the air temperature becomes too high or too low. These controllers come in a wide range of sizes and varying functionalities that control several devices in a building.

Interoperability - Building Systems Working Together For the Enterprise

Imagine the following scenario. A tenant or employee enters their
building after hours by presenting a card to a reader, or entering a
code on the keypad, at the main entrance. At that point several
things happen. The door unlocks. The HVAC system is notified
that the individual’s office on the 5th floor needs to have its temperature
setpoints changed to normal occupancy values so the
individual is comfortable when they arrive. The lighting system is
notified to turn on the appropriate lights for the office area on the
5th floor so the individual feels safe. Property management or the
accounting department is notified of the exact time when the
individual enters and leaves the building, so they can be billed for
after-hours energy usage. Everyone benefits.

Today’s facility executive wants to purchase systems and components
from various manufacturers and have those components
work together as one system. They want "open systems" that
allow the manufacturers to offer new features and add value without
locking the owner into a single vendor’s proprietary protocols.
In short, they want Interoperability.

Interoperability allows disparate systems to work together to
deliver application solutions not possible with separate,
proprietary offerings.

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Remotely Access Your Building Automation System

Remotely accessing a Building Automation System via the internet is an effective tool for operating and maintaining your system. Many solutions are available in the marketplace today ranging from 3rd party software like Symantec’s pcAnywhere or Laplink’s Laplink Gold to web based solutions like LogMeIn, GoToMyPC or WebEx’s PCNow. An often overlooked no cost solution is Microsoft’s Remote Desktop Connection (RDC).

If your building automation system has a broadband internet connection, a router and has Windows XP Pro or Windows Vista installed on it, you can access it from any other computer running Windows from anywhere in the world using Remote Desktop Connection. Remote Desktop software is pre-installed with Windows XP and Vista. The other versions of Windows, like ‘98, Me, and 2000 do not have Remote Desktop included however the software is available as a free download from Microsoft.

A few steps are required to configure your building automation system to accept connections from outside computers and additional security measures are required to keep your system safe from people who might be scanning for computers with RDC installed.

SETUP “STRONG” PASSWORDS
Remote Desktop relies on Windows passwords for login. If you currently do not have a password, or if your password is not “strong”, change it. At a minimum, your password should be 10-12 characters long, with a combination of letters, numbers and special characters. Change the password for your Windows user account from the Users section of the Control Panel. Finally, don’t forget to setup strong passwords for all your energy management, access control and CCTV applications.

ENABLE REMOTE DESKTOP
First, we must enable Remote Desktop on the building automation system. Open System Properties by right clicking the My Computer icon in the Start menu and choosing properties or Windows Key + Pause/Break on your keyboard. Click the Remote tab in System Properties and check the box next to Allow users to connect remotely to this computer.

CONFIGURE YOUR ROUTER
If your router still has the factory default password, change it. Again, a strong password of 10-16 characters, with a combination of letters, numbers and special characters is advised.
The next step in the procedure is to configure your router to allow inbound connections to Remote Desktop on your building automation computer. This requires mapping a port on your router to a port on your local computer. The process is called “port forwarding” and it varies depending on the type of router, but in general there are a similar series of steps. Routers made by Linksys refer to the port forwarding page as Applications & Gaming, most other routers refer to port forwarding options as Virtual Servers. To forward a router port to your building automation system your need to configure it as follows:

• Application or Description field: Remote1 (for example)


• Port Range Start: 3389


• Port Range End: 3389


• Protocol Type: Both (or TCP if a both option isn't available)


• IP Address of your BAS: Type ipconfig at the command line if you don't know this.


• Enable: check a box to enable the port forward

TEST YOUR CONNECTION
To test the RDC connection you will need to access your BAS remotely but first you will need to know the Internet or WAN IP address provided by your ISP to make the connection. You can usually be found by reviewing the status page of your router or you can find it at: http://whatismyip.com/.

To run Remote Desktop from a remote location using Windows XP, start the Remote Desktop Connection as follows: click Start, click All Programs, click Accessories, and then click Remote Desktop Connection. You should now be able to logon and operate your building automation system as usual.

CONCLUSION
The remote desktop connection is a free (included in XP Pro and Vista), reliable and fairly secure tool that allows you to access your building automation system. These computers can be located anywhere in the world – provided you have network access and appropriate permissions on the building automation computer.