2.2 Cables
BACnet MS/TP
We recommend that the maximum cable length within a BACnet
MS/TP segment is 1200 meters (4000 ft) with a 0.82 mm2 (AWG
18) cable.
Connection between the BACnet modules must be made by using a
screened, twisted-pair cable with a characteristic impedance
between 100 and 130 Ω.
Use a screened, twisted-pair cable and connect the 3
wires according to below table:
Terminal
Recommended
colour
Data signal
1A
Red
Positive
1B
Green
Negative
Y1
Grey
Ground
The wiring must follow the ANSI/ASHRAE BACnet standard. The
standard states that the cable screen must only be earthed at one
end of the segment to prevent earth fault currents.
BACnet IP
Use RJ45 plug and Ethernet cable. If available, connect the cable
shield to protective earth at both ends.
The standard cable length is max. 100 meters.
2.3 Device Object Instance Number
The Device Object Identifier value consists of two components:
•
a 10-bit Object Type (bits 22 to 31)
•
a 22-bit Instance Number (bits 0 to 2)
The Object Type is fixed and determines that it is a Device Object.
The Instance Number is a numeric code used to identify the device.
It must be unique inter-network-wide, that is on all interconnected
networks.
The MIXIT unit offers two different approaches to setting the
BACnet Device Object Instance Number: default and custom, both
described in the following subsections.
2.3.1 Default Device Object Instance Number
The Default Device Object Instance Number for the MIXIT unit is
227000. You can change the number via Grundfos GO Remote.
2.3.2 Custom Device Object Instance Number
The MIXIT unit uses a custom Device Object Instance Number,
which is 231. You can activate the number via Grundfos GO
Remote and change it via AV,0.
ID
Object name
R/W
AV,0
Config Custom Device Object Instance
Number
R/W
7
English (GB)
