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Power
The DNT-T221 requires a 24V AC Class 2 power supply rated for at least 15 VA. This includes output
loading of the internally powered triac (0.5A max @ 24 VAC) and the two analog outputs (20mA max each).
More than one device – not including DCUs or V2 products – may be connected to the same transformer, if
the transformer is properly sized (including line losses), and the polarity is observed between controllers (in
regards to 24~ and GND). The transformer must ONLY be used to provide power to other MS/TP or
LINKnet devices and field devices powered through its outputs. Auxiliary field devices (i.e., 4-20 mA
devices) that don't use ½ wave rectification must be powered separately.
For more information refer to the Delta Controls Wiring and Installation Guidelines.
Network & Cabling Requirements
Adhere to the following network and cabling requirements to ensure network stability and reliable
communications, particularly at high speeds on the RS-485 MS/TP or LINKnet networks.
Item
Description
Cabling
For MS/TP and LINKnet networks it is recommended that you use network cabling that
matches the following specifications:
• Balanced 100 to 120 Ω nominal impedance Twisted Shielded Pair (TSP) Cable
• Nominal capacitance of 16 PF/FT or lower
• Nominal velocity of propagation of 66% or higher
Topology
For MS/TP and LINKnet networks, ensure the cable is installed as a daisy-chain from one
device to the next.
• MS/TP: The maximum number of devices per MS/TP network without any repeaters is 50 .
Max. Nodes
• LINKnet: Up to a maximum of 12 Devices (depending on the controller), only two of
which can be DNT or DFM devices. (Refer to the Appendix on Working with MS/TP
and LINKnet in the Technical Reference Manual for more information.)
• MS/TP: A termination resistor must be jumper selected at each end of each MS/TP network
Termination
segment. Ensure you do not overlook this in laying out your network architecture.
Boards
• LINKnet: Jumper select a termination resistor on each end of the network when there
are more than 2 nodes. Termination resistors do not need to be installed for one or two
nodes.
• MS/TP: A repeater (RPT-768) is not necessary unless more than 50 nodes will be installed
Repeater
on a network or you need to extend the network beyond 4000 ft (1220 m).
• LINKnet: Repeaters should not be necessary. Ensure the maximum distance is no
more than 1000 ft (300 m).
For more information refer to the Delta Controls Wiring and Installation Guidelines .
Document Edition 1.8
Delta Controls
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