Engineering Documentation

Chapter 4 – Equipment Controllers
BACnet DXR2 Room Automation Station
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Pressurized room with or without Fume Hoods (MSTP)
For Critical Environment DXRs in a pressurized space:
● The DXR2M controllers should have their MSTP ports connected per 1.5 pair
recommendations, see MS/TP Connection [➙ 134].
● DXR2.M17xx controllers have a second RS485 port called FCOM.
● Each pressurized space will have its own FCOM bus. The FCOM ports of all
controllers in a pressurized space should be connected, including the DXR2 with
the room HVAC coordination application.
● The number of DXR2M devices on FCOM is determined by the number of remote
room segments (CetRSegm). The maximum number is 5 remote room segments.
● A single pressurized space may include up to 5 Fume Hoods (1 segment each) if
there are no remote room segments.
● DXR2.M17C handles 1 room segment. DXR2.M17CX handles 2 room segments.
● BACnet addresses for controllers in the pressurized space should be contiguous.
● Max Master must be 30 or less.
● The exception to the 5 remote segment limit is if the MSTP network is dedicated to
the single pressurized space, either with connection at a field panel or with a
router. In this case, the limit is 8. The BACnet addresses must be contiguous with
the max master set to the highest address, <= to 8.
Fig. 72: Lab MS/TP with Fume Hoods