Document Part # 026-4703 Rev 8 10-JUN-2009
Page 11 of 18
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Installation Instructions: Control Link ACC Anti-Condensate Controller System
technical bulletin
MODBUS Networks and Daisy-Chaining
Control Link ACC must be networked in a single open communi-
cations loop, or
daisy chain
. A daisy chain connects all the Con-
trol Link ACCs together in a single unbranched series, and
requires termination jumpers to be set on the controllers at either
end of the chain. No branching or “star configurations” are
allowed.
Step 1: Open the Control Link ACC Enclosure
Connecting a Control Link ACC to a MODBUS network
requires you to remove the top cover from the Control Link ACC
enclosure.
Press down the tab at the top end (power wiring side) of the enclosure, and remove front cover of the
Control Link ACC. If the Control Link ACC is already mounted in the case mullion, you may have difficulty
removing the front cover; if so, loosen the top mounting screw before pressing the tab.
Step 2: Connect the MODBUS Network Cable
MODBUS network cable has two conductors plus a shield.
For each Control Link ACC, connect the two conductors to
the 485+ and 485- terminals of the MODBUS connector (at
the bottom of the enclosure), making sure to use the same
wire colors for each Control Link ACC connection. For
example, if the conductor wire colors are BLACK and
WHITE, use BLACK for all 485+ terminals and WHITE for
all 485- terminals (or vice-versa). Connect the bare
(SHIELD) wire to the center (0V) terminal.
Step 3: Set the Network Address
NOTE: If you are networking Control Link ACC only for purposes of sharing a dewpoint sensor, you do not need
to set a network address. Set all network address dip switches or jumpers to the DOWN (OFF) position. This
will allow the Control Link ACC to share a dewpoint sensor as long as the network is physically present and ter-
minated correctly. The network address is only necessary for assigning a network ID for MODBUS applications.
Depending on the hardware revision, the Control Link ACC board has either eight dip switches or eight three-pin
jumpers, located in between the controller and network status LEDs. Switches or jumpers 1-6 set the network ID
for the controller. Switches 7 and 8 set the network baud rate and parity.
Each Control Link ACC that will use the MODBUS network must have a unique network ID. Number each con-
troller in sequence, starting with 1. Refer to
Figure 17
for dip switch and jumper settings.
WARNING! Disconnect the supply power
from the Control Link ACC before opening the
enclosure. Opening the enclosure while the
Control Link ACC is powered may result in
electrocution.
Figure 15 - Control Link ACC Daisy Chain
ACC
Figure 16 - Control Link ACC Network Connection
ACC
