Navien Modbus/BACnet Gateway, Руководство по установке и эксплуатации

Страница: 8 / 39

8 INTERFACING GATEwAy TO DEVICES
4.3 Bias Resistors
R1 Bias Resistor DIP
Switches (2 and 3)
R2 Bias Resistor DIP
Switches (2 and 3)
Figure 7: Bias Resistor DIP Switches
To enable Bias Resistors, move both the BIAS- and BIAS+ dip
switches to the right as shown in Figure 7.
The gateway bias resistors are used to keep the RS-485 bus to a
known state, when there is no transmission on the line (bus is
idling), to help prevent false bits of data from being detected. The
bias resistors typically pull one line high and the other low - far
away from the decision point of the logic.
The bias resistor is 510 ohms which is in line with the BACnet spec.
It should only be enabled at one point on the bus (for example, on
the field port were there are very weak bias resistors of 100k). Since
there are no jumpers, many gateways can be put on the network
without running into the bias resistor limit which is < 500 ohms.
Note
●
See www.ni.com/support/serial/resinfo.htm for
additional pictures and notes.
●
The R1 and R2 DIP Switches apply settings to the
respective serial port.
●
If the gateway is already powered on, DIP switch
settings will not take effect unless the unit is power
cycled.
4.1 NFB-301C/399C boiler Connections to
Gateway
Connect the 3-pin Phoenix connector of the
R1
port (gateway) to
the 3-pin terminal block located on the right side of the front panel
(Boilers).
Note
●
Make sure that the R1 Switch 4 is set to the OFF
position.
●
Use standard grounding principles for RS-485 GND.
1 2
O N
ON
1
2
+
A
B
G
TX +
RX -
GND
R2
R1
3-Pin
Terminal
Block
3-Pin
Phoenix
Connector
+
-
GND
Boiler
(Front Panel)
Gateway R1 Terminal
Pin
Assignment
A TX + RS-485 +
B RX - RS-485 -
G GND RS-485 GND
Figure 5: RS-485 Connections from Boiler to the Gateway
4.2 Wiring Field Port to RS-485 Serial
Network
●
Connect the RS-485 network wires to the 3-pin RS-485
connector on the R2 port. (Figure 6)
-
Use standard grounding principles for RS-485 GND.
●
See Section 5 for information on connecting to an Ethernet
network.
BMS
Wiring
Gateway
R2 Terminal
Pin
Assignment
RS-485 + + RS-485 +
RS-485 - - RS-485 -
- G RS-485 GND
Figure 6: Connection from Gateway to RS-485 Field Network
4. INTERFACING GATEWAy TO DEVICES