CONTROL PROTOCOLS FOR BUILDING AUTOMATION
ISSUE:
Open protocols versus Proprietary Protocols.
BACKGROUND:
In the past, a successful bidder control company used its proprietary system for installation
of an automatic temperature control system. The exclusive features of a proprietary system
narrowed competition and drove up the cost. They had a virtual lock on any addition to the
system. The owner had no choice but to go to the same company for additional work and
pay a heavy price.
Out of this quandary, which has characterized the controls industry for over 30 years, was
born the present thrust toward open systems. These allow control system components of
different design and manufacturer to interact with each other, thus allowing competition and
reducing cost.
DISCUSSION:
In the commercial market, two most common open protocols have emerged, LONWORKS
and BACnet. The Echelon Corporation developed LONWORKS and BACnet was developed
by ASHRAE. These two standards offer alternate approaches to the common goal of
openness. Each gives a different kind of flexibility. The industry is divided over their
preference in use of these two protocols. VA recommends use of both protocols, each for
different level of controls. VA Master Specification was updated consistent with this
recommendation.
RECOMMENDATIONS:
For new, and existing systems with significant planned expansion:
1. Specify LONWORKS for unitary controls (VAV boxes and other terminal controls)
and equipment controls (mechanical room controls).
2. Specify BACnet for communication between various buildings i.e., for interbuilding
communication.
LINKS TO FM TECHNICAL INFORMATION LIBRARY (TIL):
See VA Master Specification, Section 15902, Controls and Instrumentation (DDC)
http://www.va.gov. /facmgt/standard
FOR ADDITIONAL INFORMATION:
Contact Satish Sehgal at 202-565-5032, in the Facilities Quality Service (181A);
satish.sehgal@hq.med.va.gov.
19 JUNE 2002
FM-181A-DA-111
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