HEATING, VENTILLATION, AND AIR CONDITIONING

Climate Control Systems

If clean air is the blood of a building then HVAC systems are the heart. They ensure that we are comfortable in extreme weather conditions. They maintain an acceptable level of carbon dioxide and other pollutants within the building. If designed and implemented correctly they will do all this and more while spending the least amount of energy.

DDC stands for Direct Digital Control. In the simplest terms it is a control system that uses a computer, or many computers linked together via a network, that control the infrastructure of a building.

They are similar to a PC but have no hard drive, monitor or keyboard. They are specifically designed for building systems such as HVAC, security, CCTV, fire and asset management. They monitor inputs such as temperature, card readers, pull stations and output signals to control heating valves, open doors, and sound alarms.

The functions they provide are as simple as controlling room temperature in an office to linking together an entire campus of buildings with a central power plant.

DDC control systems today have become the standard in buildings for maintaining the environment. 10 years ago DDC was a luxury to owners and building managers. Not today. We have proven time and time again that DDC is just as cost effective to implement compared to traditional control systems such as electric or pneumatic.

DDC systems offer several benefits to the building owner or manager:

• Central monitoring and control

  Software on a PC can help operators monitor HVAC systems from a central location. This allows instant operator interaction with building's system or many systems. They can provide a picture of what is going on in the building via a computer screen. They can also change system operation from the same central location. These operations could include opening/closing valves, starting/stopping fans, or changing setpoints to name a few.

• Alarm Management

  Networked DDC systems communicate alarm conditions to central and/or remote locations. Alarm management features help operators assess the situation and, in many cases, provide the necessary actions to take in response.

• Trending and History Event Monitoring

  Most, if not all, DDC systems provide some type of data management and analysis tools. These utilities can be used to create trends for critical or problem areas. Commonly trended data inlcudes temperature, pressure, humidity, time and source of operator commands, and many others. Data can be recorded by the second, for an hour, a day, or even a year or more. The resulting information can then be viewed as graphs, spreadsheets, or even customized user-defined reports. This data is persisted in the central monitoring system for later review and is critical to the proper tuning of a building's DDC systems for optimal performance and efficiency.

• Energy Management

  DDC systems, being digital, are of course electronic and thus use electronic circuits and devices to enable their monitoring and control abilities. Technology is forever changing and better sensors for measurement and device control are constantly emerging. Compared to a pneumatic sensor, which has an accuracy of ± 2°F, typical DDC sensors are currently accurate to ±0.3°F. To put this in context, imagine you have an air system that must cool 100,000 CFM of air. The improved accuracy of a DDC system would save over 150,000 BTUs/hr, or 46kW of energy.

• Lower Costs

  Ten years ago DDC systems were big and expensive. They were only cost effective for major systems in large buildings or campus environments. Today's modern DDC controllers are 10% the size and 20% of the cost that they used to be. For example, the cost of an air system DDC controller 10 years ago was between $3,000 and $8,000 US. Today that same controller costs approximately $1,000 to $3,000. Accounting for inflation you can see how the prices have dropped.