Siemens QNA2 D Series Commissioning page 12

4
BACnet MSTP setup
Daisy chain wiring
Using terminals A+ and B-, connect the in-wall mounts to the BACnet router (or other BACnet devices) in a
daisy chain topology. Ensure that the power is shut off during wiring.
A+, B- Twisted pair
G Reference wire
Shield
Examples of recommended cable types
Capacitance
39 pF/m
12 pF/ft
41 pF/m
12.5 pF/ft
43 pF/m
13.1 pF/ft
Notes:
1) Foil + Braid is recommended for harsh environment (mechanical and electromagnetic interference, e.g.
variable speed drives).
2) 2-pair cable to be used with care because of different color scheme.
The two conductors of the second pair must be wired in parallel to the reference terminal to prevent a floating
conductor.
12 | 16
120 Ohm Bus terminating resistor (½ W 5 %) at BOTH ends
PTC Special-thermistor (TRF250-120) at ONE end
1)
Shield
Foil + Braid
Foil + Braid
Foil
Temperature
80 ° C
80 ° C
80 ° C
Pairs
1.5
2)
2
2)
2
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