HVAC System Control > Building Automation System

Existing Conditions

The existing equipment is under pneumatic, electric, or manual control that is very basic and may not work well. With this type of control, equipment runs longer than necessary to cover all possible expected operating conditions. These controls are subject to tampering when they fail to perform well, and cannot be set up with the energy-saving strategies available with modern digital controls.

Retrofit Conditions

We suggest replacing existing controls with a building automation system (BAS). The system would be programmed at the time of installation according to energy-conserving strategies specified by the design engineer.

BAS systems can be thought of as computer networks, with miniature computers controlling the important pieces of mechanical equipment. These computers talk to each other through the network to enable interaction with one another according to central control logic and to allow central oversight and centrally-managed features. BAS systems can include many safety and convenience features such as full graphic terminal operation, remote access via internet, dial out/e-mail of alarms, security monitoring, and trending of energy and equipment data. To get all the features of a full BAS system can be quite expensive, however it is possible to start small and expand the control network over time. For the purpose of this study, we are recommending the most cost-effective approach, which is the installation of a BAS system intended to save energy. Further components can be added at a later date.

The cost of a system is closely tied to the number of control "points": physical input and output devices such as temperature sensors and relays. Mechanical system schematics provided elsewhere in this report show the recommended control points.

Further Benefits

BAS systems can include many safety and convenience features such as full graphic terminal operation, remote access via phone line, ethernet LANs, WANs, internet, intranet for alarms, security monitoring, and trending of energy and equipment data.

Online data exchange with database tools such as Oracle and Microsoft SQL database servers can facilitate and automate information exchange between large systems for services such as scheduling. These tools may also be used to interact and exchange data with financial models to further analyse energy use, and management applications.

Application Details

Issues and Concerns

Because building control is intimately tied to building operations and maintenance, and because these systems are often expanded and modified over time, it is not in the building owners' interests to find themselves locked in with a single supplier. However this is a very real risk. The building automation industry has been much slower to adopt technical standards than the personal computer industry, so it can be a challenge to keep future supplier options open. To limit this risk, there are two considerations that the building owner should think about:

Number of Local Suppliers: How many sources are able to procure, install, and program the particular line of control hardware? Avoid a system with only one capable contractor in the area.

Communication Standard: Pick a system that conforms with a widely accepted communication standard. This will mean that many of the smaller components will be interchangeable among a number of manufacturers. The two most prevalent building automation communication standards are BACnet and LONworks.

Interoperability: Can the new system interface with packaged system controls such as rooftop units, chillers, boilers, himidifiers, heat pumps, VFD's, etc. by digital means.

References

ANSI/CEA-709.1 standardization accepted

Analysis

Building automation control has evolved rapidly in the last few years with costs dropping significantly. It is difficult to determine the "per point" cost of BAS because bundled points included with HVAC equipment are inherited when common network connections are made.

A range of $400 to $700 per point is common, depending on the mix of included points and installation quality standard. This estimated range includes real or physical points only and does not include the large number of virtual points included within the software. These estimates include remote communication to a networked personal computer and operating software.