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Application
Line voltage terminals.
Keyboard Display Module 22 AWG two-wire twisted pair with ground, or five-
Data ControlBus™
a
Module
Remote Reset Module
13 Vdc full-wave rectified
transformer power input.
a
The KDM or Data ControlBus™ Module (for remote mounting or communications) must be wired in daisy chain configu-
ration, 1(a)-1(a), 2(b)-2(b), 3(c)-3(c). The order of interconnection of all the devices listed above is not important. Be
aware that modules on the closest and farthest end of the daisy chain configuration string require a 120 ohm (1/4 watt
minimum) resistor termination across terminals 1 and 2 of the electrical connectors for connections over 100 feet (31
meters).
Ground Type
Earth ground (subbase and relay
module).
Signal ground (Keyboard Display
Module, Data ControlBus™ Module.
9.
Maximum wire lengths:
a. RM7897A,C leadwires: The maximum leadwire
length is 300 feet to terminal inputs (Control,
Running/Lockout Interlock).
b. Flame Detector leadwires: The maximum flame
sensor leadwire length is limited by the flame
signal strength.
c. Remote Reset leadwires: The maximum length of
wire is 1000 feet (305 meters) to a Remote Reset
push button.
d. Data ControlBus Module™: The maximum Data
ControlBus™ Module cable length depends on
the number of system modules connected, the
noise conditions and the cable used. The
maximum length of all Data ControlBus™
Module interconnecting wire is 4000 feet (1219
meters).
10. Be sure loads do not exceed the terminal ratings.
Refer to the label on the RM7897A,C or to the termi-
nal ratings in Table 3.
Table 1. Recommended Wire Sizes and Part Numbers.
Recommended Wire Size
14, 16 or 18 AWG copper conductor, 600 volt
insulation, moisture-resistant wire.
wire.
22 AWG two-wire twisted pair with ground, or five-
wire.
22 AWG two-wire twisted pair, insulated for low
voltage.
18 AWG wire insulated for voltages and
temperatures for given application.
Table 2. Recommended Grounding Practices.
1. Use to provide a connection between the subbase and the control panel of the
equipment. Earth ground must be capable of conducting enough current to
blow the
15A, type SC,. fast blow fuse (or breaker) in the event of an internal short circuit.
2. Use wide straps or brackets to provide minimum length, maximum surface area
ground conductors. If a leadwire is required, use 14 AWG copper wire.
3. Make sure that mechanically tightened joints along the ground path are free of
nonconductive coatings and protected against corrosion on mating surfaces.
Use the shield of the signal wire to ground the device to the signal ground terminal
3(c) of each device. Connect the shield at both ends of the daisy chain to earth
ground.
RM7897A,C 7800 SERIES RELAY MODULES
Recommended Practice
Final Wiring Check
1. Check the power supply circuit. The voltage and
frequency tolerance must match those of the
RM7897A,C. A separate power supply circuit can be
required for the RM7897A,C. Add the required
disconnect means and overload protection.
2. Check all wiring circuits and complete Static
Checkout in Table 6 before installing the
RM7897A,C on the subbase.
3. Install all electrical connectors.
4. Restore power to the panel.
STATIC CHECKOUT
After checking all wiring, perform this checkout before
installing the RM7897A,C on the subbase. These tests
verify the Q7800 Wiring Subbase is wired correctly, and
the external controllers, limits, interlocks, actuators,
valves, transformers, motors and other devices are
operating properly.
7
Recommended Part Numbers
TTW60C, THW75C, THHN90C.
Belden 8723 shielded cable or
equivalent.
Belden 8723 shielded cable or
equivalent.
—
TTW60C, THW75C, THHN90C.
32-00158—03
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