RM7838B,C 7800 SERIES RELAY MODULE
5 66-1094—08
Table 1. Recommended Wire Sizes and Part Numbers.
Table 2. Recommended Grounding Practices.
The KDM and Data ControlBus™ Module (for remote
mounting or communications) must be wired in a daisy chain
configuration, 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).
4. See Table 2 for recommended grounding practices.
5. Use recommended wire routing of leadwires:
a. Do not run high voltage ignition transformer wires in
the same conduit with the flame detector, Data
ControlBus Module™, or Remote Reset Module
wiring.
b. Do not route flame detector, Data ControlBus
Module™, or Remote Reset Module leadwires in
conduit with line voltage circuits.
c. Enclose flame detector leadwires without armor
cable in metal cable or conduit.
d. Follow directions in flame detector, Data ControlBus
Module™, or Remote Reset Module Instructions.
6. KDM: Because the KDM is powered from a low voltage,
energy limited source, mount it outside of a control
panel if it can be protected from mechanical damage.
NOTE: Use a separate 13 Vdc power supply any time more
than two Data ControlBus Modules™ or KDM are
used or are placed more than 100 feet (31 meters)
from the relay module.
7. Use maximum wire lengths:
a. RM7838B,C leadwires—300 feet (91 meters) to
terminal inputs (Control, Preignition Interlock,
Running/Lockout Interlock, High Purge Switch and
Low Fire Switch).
b. Flame Detector leadwires—limited by the flame
signal strength.
c. Remote Reset leadwires—1000 feet (305 meters) to
a Remote Reset push button.
d. Data ControlBus™ Module—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).
8. Make sure loads do not exceed the terminal ratings.
Refer to the label on the RM7838B,C or to the ratings in
Table 4.
FINAL WIRING CHECK
1. Check the power supply circuit. The voltage and fre-
quency tolerance must match those of the RM7838B,C.
(A separate power supply may be required for the
RM7838B,C.)
2. Add the required disconnect means and overload
protection.
3. Check all wiring circuits and complete the static
checkout in Table 3 before installing the RM7838B,C on
the subbase.
4. Install the relay module.
5. Restore power to the panel.
STATIC CHECKOUT
After checking all wiring, perform this checkout before
installing the RM7838B,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.
Application Recommended Wire Size Recommended Part Numbers
Line voltage terminals 14, 16 or 18 AWG copper conductor, 600 volt
insulation, moisture-resistant wire.
TTW60C, THW75C, THHN90C.
KDM 22 AWG two-wire twisted pair with ground, or five-wire. Belden 8723 shielded cable or equivalent.
Data ControlBus Module™ 22 AWG two-wire twisted pair with ground, or five-wire. Belden 8723 shielded cable or equivalent.
Remote Reset Module 22 AWG two-wire twisted pair, insulated for low voltage. —
13 Vdc full wave rectified
transformer power input.
18 AWG wire insulated for voltages and temperatures
for given application.
TTW60C, THW75C, THHN90C.
Ground Type Recommended Practice
Earth Ground (Subbase and relay
module)
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 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 lead wire must be used, 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.
Signal Ground (KDM, Data ControlBus
Module™
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.
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