5168274-BIM-I-1121
Johnson Controls Ducted Systems
47
J15
Factory wired SA Bus connector
Optional communication sub-board at center of UCB
Terminal FC BUS
1
connections on left edge of the communication board
FC+
FC (“Field Connected”) BUS BACnet MSTP
communication
Positive of the VDC (typically, a fluctuating 1.5 to 3.5 volts
reading to COM; at least 0.25 volts higher than
–
) FC bus
BACnet MSTP communication circuit
FC–
FC (“Field Connected”) BUS BACnet MSTP
communication
Positive of the VDC (typically, a fluctuating 1.5 to 3.5 volts
reading to COM; at least 0.25 volts lower than +) FC bus
BACnet MSTP communication circuit
COM
Common for the FC (“Field Connected”) BUS
BACnet MSTP communication circuit
Negative of the VDC FC bus BACnet MSTP communication
circuit
SHLD
Shield for the FC (“Field Connected”) BUS
BACnet MSTP communication circuit
Earth ground reference of the cable to prevent interference on
the FC bus BACnet MSTP communication circuit
Item Selector in red housing at left on top edge of the communication board
EOL
switch
End Of Line selector switch for the FC BUS
BACnet MSTP communication circuit
ON selected only for the UCB that is the terminus of the FC bus
BACnet MSTP communication cable to prevent signal “bounce-
back”
LEDs on the communication board
EOL
Green End Of Line indicator
Lit indicates the EOL switch is selected ON
FC BUS
Green FC bus communication transmission
indicator
Lit/flickering indicates outgoing UCB FC bus communication is
currently active, off indicates the UCB is awaiting incoming FC
bus communication
ISO PWR
Green communication board Isolated Power
indicator
Lit indicates the UCB is supplying power to the communication
sub-board
1. When wiring unit and other devices using the SA Bus and FC Bus, see Table 20.
Table 19: Smart Equipment™ UCB Details (Continued)
Description
Function & Comments
Table 20: Cable for FC Buses and SA Buses in Order of Preference
Bus and Cable Type
Non-Plenum Applications
Plenum Applications
Part Number
O.D.
Part Number
O.D.
FC Bus:
22 AWG Stranded, 3-Wire Twisted Shielded Cable
1
Anixter:
CBL-22/3-FC-PVC
Belden®: B5501FE
0.138 in.
Anixter: CBL-22/3-FC-PLN
Belden: B6501FE
0.140 in.
SA Bus (Terminal Block):
22 AWG Stranded, 4-Wire, 2 Twisted-
Pair Shielded Cable
Anixter:
CBL-22/2P-SA-PVC
Belden: B5541FE
0.209 in.
Anixter: CBL-22/2P-SA-PLN
Belden: B6541FE
0.206 in.
SA Bus (Modular Jack):
26 AWG Solid 6-Wire, 3 Twisted-Pair Cable
2
—
—
Anixter preassembled: CBL-
NETWORK25 CBL-
NETWORK50 CBL-
NETWORK75 CBL-
NETWORK100
0.15 in.
FC Bus:
22 AWG Stranded, 3-Wire Twisted Non-Shielded Cable
Belden: B5501UE
0.135 in.
Belden: B6501UE
0.131 in.
SA Bus (Terminal Block):
22 AWG Stranded, 4-Wire, 2 Twisted-
Pair Non-Shielded Cable
Belden: B5541UE
0.206 in.
Belden: B6541UE
0.199 in.
1. We strongly recommend 3-wire (for FC bus) and 4-wire, 2 twisted-pair (for SA bus), 22 AWG stranded, shielded cable. A 22 gauge cable
offers the best performance for various baud rates, cable distances, and number of trunk devices primarily due to lower conductor-to-
conductor capacitance. Shielded cable offers better overall electrical noise immunity than non-shielded cable. Observe the shield
grounding requirements.
2. We recommend 26 AWG solid, 6-wire (3 twisted pairs) cable as the best fit for fabricating modular cables with the modular jack housing
assembly. Be sure the cable you use fits the modular jack housing. The preassembled cables that are available from Anixter (Part No.
CBL-NETWORKxxx) use 24 gauge wire.
