VCES-DDC-IOM-1C
19
Unit Control
The unit can be enabled in ventilation mode by jumpering
FW 304 to 305. Alternatively the software point MV12 can
be used to schedule the unit. If this method is being used
then you must not provide any jumpers to terminals 304,
305, 306, 307 or 308.
The remote unit control multi-state variable is used to en-
able the unit through a Bacnet interface.
Set MV12 to:
• 2 for unoccupied mode.
• 4 for occupied recirculation mode (optional).
• 6 for unoccupied recirculation mode (optional).
• 10 for ventilation mode.
BacNet Interface
Interface to the DSC-1180 controller by connecting to the
“Net 1” terminal as seen below.
Networking Specifications
Venmar CES provides equipment with network integration
features. The following section outlines basic practices as
recognized in the industry. As an HVAC equipment manu-
facturer, it is not part of Venmar CES’ mission to provide
exhaustive networking design and integration services. In all
cases, the advice and services of a networking professional
for network design and integration should be employed.
The DDC controllers provided along with Venmar CES
equipment will support two types of network connection:
• RS232 (generally used for temporary local access to
unit controller – i.e. troubleshooting)
• RS485 – the following specifications pertain to RS485
connection
Most commonly, RS485 is used as the physical layer be-
tween panels and unit controllers in HVAC networking
applications. See Table C1 for a summary of specifications
concerning the application of RS485 networks.
Cable Type
Venmar CES recommends the use of balanced 22 to 24
AWG twisted pair with a characteristic impedance of
100–120 ohms, capacitance of 17 pF/ft or lower, with a
braided shield.
Network Configuration
RS485 networks use a daisy chain configuration (only one
main cable, every device being connected directly along
its path).
Figure C2 illustrates two improper network configurations
and the proper daisy chain configuration.
Note that there are no troubleshooting methods for these
improper types of networks.
The use of an improper network configuration may result
in undesirable and unpredictable effects on unit function-
alities.
Only the daisy chain configuration is correct for a RS485
network. Figure C3 shows connection in the middle of a
daisy chain.
Appendix C: Standard Network Practice
Net 1
BacNet terminals
Figure C1: BacNet interface
Star configuration Bus configuration
Daisy chain
configuration
Figure C2: Network configurations – star, bus and daisy chain
Table C1: Summary of Specifications for a RS485 Network
Category Specification
Cable type
100–120 ohm balanced, twisted
shielded pair
Network configuration Daisy chain
Maximum distance of
chain
4,000 ft [1,200 m]
Maximum stub length 10” [0.25 m]
Minimum spacing
between devices
12” [0.30 m]
Maximum number of
devices
32 devices per daisy chain segment
Termination
Termination use DNT294 network
terminator at both ends of a segment
Shielding
Connect shield to DNT294 network
terminator
IMPORTANT
Values shown are based on starting at a count of one.
When using Johnson Controls/Metasys, set the values
one lower than shown as they start at zero.
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Comentarios a estos manuales