Installation Guide

TP-7091 2/21 29Section 3 Electrical
3.3 ATS and Accessory
Communication Connections
The following sections cover communication
connections from the generator set to automatic transfer
switches and RBUS accessories, including the
programmable interface module (PIM) and the load
shed kit.
3.3.1 Communication Cable
Specifications
RBUS Connections A and B
For the RBUS communication connections A and B to
the optional RBUS modules, use 20 AWG shielded,
twisted-pair communication cable. Belden #9402
(two-pair) or Belden #8762 (single-pair) or equivalent
cable is recommended. Optional RBUS modules can
include the Model RXT transfer switch, RXT combined
interface/load management board, automatic
paralleling module (APM), programmable interface
module (PIM), and/or the load shed kit for the RDT or
RXT transfer switch.
For outdoor installations, including those with buried
cables and/or conduit, use outdoor-rated Belden
#1075A or equivalent 20 AWG shielded, twisted-pair
communication cable.
PWR and COM Connections
For the PWR and COM connections, the cable size and
maximum cable length depends on the number of
modules connected. See Figure 3-6.
 For short cable runs shown in the first two rows of
Figure 3-6, use one pair in the two-pair
communication cable for the A and B connections,
and use the second pair for the PWR and COM
connections.
 For the longer cable runs shown in the last two rows of
Figure 3-6, use 12 or 14 AWG cable for PWR and
COM, and use the 20 AWG communication cable
specified above for the A and B connections only. In
this case, single-pair communication cable such as
Belden #8762 can be used for the A and B
connections.
3.3.2 Transfer Switch Connection
Connect the ATS or remote start/stop switch. Connect
the load leads from the generator set to the Emergency
source lugs on the ATS. Route low-voltage
communication leads through separate conduit from the
AC power and load leads. All connections must comply
with applicable state and local codes.
Communication connections for a Model RXT
transfer switch
One Model RXT transfer switch can be connected to the
generator set. See Figure 3-7. Use shielded,
twisted-pair communication cable to connect P10-1
through P10-4 on the transfer switch interface module to
the generator set terminal block connections A, B, PWR,
and COM. See Section 3.3.1 for the communication
cable recommendations and maximum cable length.
Note: Connections 3 and 4 on the generator set are not
used with the Model RXT transfer switch.
Engine start connection for other transfer
switches or a remote start/stop switch
Connect the engine start leads from the transfer switch
or remote start switch to terminals 3 and 4 on the
terminal block. See Figure 3-8. Route the engine start
leads through separate conduit from the AC power and
load leads.
Cable (TB1- PWR and COM)
Maximum length per run, meters (ft.)
Number of Modules (RXT, APM, PIM, and/or load management device) per Run
1 Module 2 Modules 3 Modules 4 Modules
Belden #9402 or equivalent 20AWG
for indoor installations
46 (150) 15 (50) 5 (17) Do not use 20AWG
for PWR and COM
Belden #1075A or equivalent 20AWG
for outdoor installations or buried
cables
46 (150) 15 (50) 5 (17) Do not use 20AWG
for PWR and COM
14 AWG *
137 (450) 137 (450) 107 (350) 107 (350)
12 AWG *
137 (450) 137 (450) 137 (450) 137 (450)
* Use 12 or 14 AWG cable for PWR and COM connections only. For RBUS connections A and B, use shielded, twisted pair communication
cable specified above.
Figure 3-6 Total Cable Lengths for PWR and COM Connections