IM 689-2
13
Power
!
WARNING
Electric shock hazard. Can cause personal injury or death.
This equipment must be properly grounded.
All protective deadfront panels must be reinstalled and secured when power wiring is complete.
The BACdrop gateway requires a 100 – 240 Vac, 50/60 Hz power supply. The panel must be properly
grounded by connecting the ground terminal (GRD) to earth ground. Refer to Figure 5. Power wiring
must be sized to carry at least 2 A.
To gain access to the high voltage section, remove the screws that secure the deadfront cover to the
panel. Replace this deadfront when the wiring is complete.
The panel is protected by a 2 A circuit breaker (CB), which is located inside the panel above the
deadfront barrier (see
Figure 1
). This push-button circuit breaker can be used as an on-off switch for
the panel. A white ring on the switch shaft is visible when the power is off.
MicroTech Network Communications
For MicroTech network communications to occur, a twisted, shielded pair cable must be connected
between the BACdrop gateway and its associated MicroTech unit or supervisory controllers. This
interconnecting, “daisy-chain” wiring is shown in Figure 5. Network communications is
accomplished using the RS-485 interface standard at 9600 baud.
For a typical BACdrop network, the BACdrop gateway is the level-1 controller and the unit
controllers are level-2 controllers. There are no level-3 controllers—except in the case of series-100
(old style) centrifugal chillers, which have a level-2 display processor and a level-3 unit control
processor.
About MicroTech Network Architecture
All controllers in a MicroTech network are assigned a
level
: level 1, level 2, or level 3. All
networks must have one level-1 controller to coordinate communications. Multiple level-2
controllers connect to the level-1 controller with a communications
trunk
. A trunk is defined
as an isolated section of the daisy-chained network wiring. In Figure 5, the network wiring
between all controllers is a trunk. Multiple level-3 controllers can be connected to a level-2
controller with a separate trunk; however, this is typically not done in BACdrop
applications.
The maximum allowable length of a communications trunk is 5000 ft (1524 m).
Cable Specification
The MicroTech network communications cable must meet the following minimum requirements:
twisted, shielded pair with drain wire, 300 V, 60°C, 20 AWG, polyethylene insulated, with a PVC
outer jacket (Belden 8762 or equivalent). Some local codes or applications may require the use of
plenum rated cable.
Do not install the cable in the same conduit with power wiring
.
Note:
Ideally, one continuous piece of cable should connect any two controllers. This will reduce the
risk of communications errors. If the cable must be spliced, use crimp-type butt connectors (better) or
solder (best). Do not use wire nuts.
