Datasheet

LTX-VCI Datasheet
LTX-VCI Iss1.05
RealTime Control Systems Ltd. Park House, Greenhill Crescent, Watford WD18 8PH. Tel [phone] Fax [phone] Page 3
Web: www.realtime-controls.co.uk , E-mail: [e-mail] LTX-VCI Datasheet Issue 1.05.01 12/07/2003 Doc No. 92101
1.3 Engineering
Engineering is a two step process, on one side connecting the VCI with the air-conditioning
Interface, on the other connecting the BMS control system via a suitable LTX controller.
To engineer a specific system, follow the instructions in this datasheet to set up the linkage to
the BMS interface and perform general configuration of the LTX-VCI. Refer to the relevant
Device Interface Sheet within this datasheet for the relevant manufacturers product, this will
provide product specific details of the available functionality and specific configuration
information. Device Interfaces Sheets are specific to the LonWorks Program ID of the
interface. If the program ID is different from that in the Device Interface Sheet then contact
RealTime as there may be compatibility issues.
The system must be engineered by a suitably trained LonWorks integrator using the correct
engineering tools. Engineers new to engineering RealTime products should contact us for
additional information. The LonWorks functional profile for the VCI is available at the rear of
this datasheet.
1.3.1 Air-Conditioning Interface
Note: Before the system is installed it is advisable to establish the unit addressing
methodology being used in the system. As a general principle it is recommended that
units are addressed from unit ‘1’ (the lowest possible address) upwards with no gaps in
the addressing scheme. Schemes that start the addressing at higher values and have
gaps in the addressing scheme are liable to create problems in the interfacing and
control of the system.
Firstly consult the Device Interface Sheet relevant to the system being installed, these are
found in this datasheet. The device interface sheet will provide device specific information on
the device functionality and any special steps that need to be taken during installation and
engineering. The Device Interface Sheet provides the relevant
VCI Mode Number for the
device in question, this value configures the VCI to the correct configuration for the selected
interface. The first task in configuring the VCI is set this value in the
Node: UCPTVCIMode . If
unsure of the value, setting
Node: UCPTVCIMode equal to 0 disables any communication with
the interface. WARNING: Using an incorrect value for
UCPTVCIMode can lead to
unpredictable behaviour of the system.
Once the VCI Mode is selected the VCI will be configured to the maximum number of indoor
units for the selected interface, should the actual number of units be less than the maximum
this it is possible to restrict the overall range of units addressed by the VCI by using the
configuration parameters
Node:UCPTMinUnitNum and Node:UCPTMaxUnitNum This will
reduce the amount of time required to scan the system in order to produce faster updates of
readback data and will also prevent invalid unit addresses from being processed.
To enable communication between the VCI and the A/C Interface create a single message tag
binding between the tag VCItag on the VCI and the standard msg_in tag on the selected A/C
interface
1
using a suitable LonWorks engineering tool.
The VCI should now be communicating with the air-conditioning interface, polling data from the
selected range of units. The VCI will not write any data to the units until it receives control data
from the BMS interface.
1
Message tags in LonMaker for Windows are found on the Virtual Function Block (VFB) of each of the devices. If adding by hand it will
be necessary to drop the VCItag
msg_out object onto the VCI VFB and a msg_in object on the a/c interface VFB to make them visible.
Connecting them as normal will bind the tags.