variable air volume (VAV) boxes, fan coil units, and heat pumps.
1.5
DDC SYSTEM DESCRIPTION
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Notes on Vendor Interoperability
The technology for sharing information between two
or more proprietary controllers is not fully
developed. It is not realistic to simply specify a
"common architecture" or gateway that seamlessly
bridges the gap of vendor specific hardware,
programming, and network communications.
It is possible, however to share relevant point
information between different manufacturer's
controllers on a case by case basis. Several
control manufactures and many manufacturers of plant
equipment, speed drives, and building security
systems have built in communication ports or
gateways for external communications. These ports
and gateways are able to communicate point
information to other vendors controllers using
proprietary or industry standard protocols. The
designer should research new and existing
controller/equipment combinations to take advantage
of this option if it is readily available.
Specifying custom gateways or new communication
ports that don't already exist commercially is
costly and will increase risk.
To increase the chance of successful
interoperability, begin with a simple design scheme
and specify only relevant shared point types and
parameters. Also specify desired actions, vendor
responsibility, operator display, and physical
wiring where appropriate. Do not expect or specify
that two or more systems will share all possible
control information.
Focus more on functionality
between systems as opposed to protocols and internal
architecture.
For less complex cases it is best to specify
interoperability directly on the controls drawings.
The following example specifies communications
between a DDC network made by Vendor "A" and
centrifugal chiller controls made by Vendor "B":
Sample Specification:
Need: The DDC network will exchange point
parameters listed in Table (1) with the chiller
controls. A parameter noted as a read point means
that the value is read at 1-minute minimum intervals
by any relevant network controller to accomplish
specified sequence of control.
A parameter noted
as a write point means the value is written at
1-minute minimum intervals by the controller network
SECTION 15910N
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