Honeywell AUTOMATIC CONTROL, Engineering Manual

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ENGINEERING MANUAL OF AUTOMATIC CONTROL
BUILDING MANAGEMENT SYSTEM FUNDAMENTALS
185
INTRODUCTION
This section provides information on the fundamentals of
Building Management Systems (BMS). The objective of a BMS
is to centralize and simplify the monitoring, operation, and
management of a building or buildings. This is done to achieve
more efficient building operation at reduced labor and energy
costs and provide a safe and more comfortable working
environment for building occupants. In the process of meeting
these objectives, the BMS has evolved from simple supervisory
control to totally integrated computerized control. Some of the
advantages of a BMS are as follows:
— Simpler operation with routine and repetitive functions
programmed for automatic operation
— Reduced operator training time through on-screen
instructions and supporting graphic displays
— Faster and better responsiveness to occupant needs and
trouble conditions
— Reduced energy cost through centralized management
of control and energy management programs
— Better management of the facility through historical
records, maintenance management programs, and
automatic alarm reporting
— Flexibility of programming for facility needs, size,
organization, and expansion requirements
— Improved operating-cost record keeping for allocating
to cost centers and/or charging individual occupants
— Improved operation through software and hardware
integration of multiple subsystems such as direct digital
control (DDC), fire alarm, security, access control, or
lighting control
When minicomputers and mainframes were the only
computers available, the BMS was only used on larger office
buildings and college campuses. With the shift to
microprocessor-based controllers for DDC, the cost of
integrating building management functions into the controller
is so small that a BMS is a good investment for commercial
buildings of all types and sizes. For additional information on
microprocessor-based controllers refer to the Microprocessor
Based/DDC Fundamentals. Building Control is discussed
further in the Air Handling System Control Applications; the
Building Airflow System Control Applications; and the
Chiller, Boiler, and Distribution System Control sections.
The examples used throughout this section are typical of what
is available and not necessarily representative of any given
installation.
DEFINITIONS
Building Control System (BCS):
A system that controls the
comfort and safety of a buildings assets and
environment.
Building Management and Control System (BMCS):
An
integrated BMS and BCS
Building Management System (BMS):
A system which
centralizes the monitoring, operations, and
management of a building to achieve more efficient
operations.
Building Automation and Control Network (BACnet)
Protocol:
A BMCS communications protocol
developed by the American Society of Heating,
Refrigerating, and Air Conditioning Engineers
(ASHRAE).
Communications Protocol:
A set of conventions used to
govern the format and content of messages between
processors.
Dynamic Display Data:
Data displayed on a BMCS work
station which periodically updates, such as
temperature or ON/OFF status. The data updates
automatically at a rate appropriate for the point or it
may be updated manually.
Energy Management System (EMS):
A system that optimizes
the operation, temperatures, and processes of an HVAC
system within a building. Except for some early
versions, a BCS or BMCS includes all EMS functions.
Hierarchical configuration:
A system in which the processors
and controllers are arranged in levels or tiers, with
each tier having a definite rank or order in accessing
and processing data. A typical arrangement includes,
in descending order, management-level processors,
operations-level processors, system-level controllers,
and zone-level controllers.
LonMark TM standard:
A communications standard for control
networks developed by the Echelon Corporation and
the LonMark™ Interoperability Association.
Management-level processor:
A PC or minicomputer used by
management personnel to collect, store, and process
data for reports on energy use, operating costs, and
alarm activity. This processor can access points or data
in all the lower level processors and controllers. (In
most cases a separate, management-level processor is
not used. Many of the functions of the management-
level processor can be combined into the operations-
level processor.)