1-12 750-166
CB780/CB784
WIRING
The shield, if used, should be connected to the
signal ground terminal 3(c) provided as part of the
CB780/CB784 device ControlBus connection.
Connect the shield at both ends to earth ground.
c. CB780/CB784—Each CB780/CB784 will have
an earth ground terminal that must be grounded to
the metal control panel with wire as short as prac-
tical. Each ground wire must be capable of carrying
a fault current equal to the rating of the protec-
tive fuse (20A). A number 14 copper conductor
is adequate, but wide straps or brackets are pre-
ferred rather than leadwires.
6. Recommended wire routing:
a. Flame detector leadwires:
1. Do not run high voltage ignition transformer
wires in the same conduit with the flame detec-
tion wiring.
2. Do not route scanner wires in conduit with line
voltage circuits.
3. Enclose scanner wires without armor cable in
metal cable or conduit.
4. Follow directions in flame detector Instructions.
b. Control Bus:
1. Do not run high voltage ignition transformer
wires in the same conduit or close proximity
with the Control Bus wiring.
2. Do not route Control Bus wires in conduit with line
voltage circuits.
c. Keyboard Display Module (VFD): Because the
VFD is powered from a low voltage, energy lim-
ited source, it can be mounted outside of a control
panel if it is protected from mechanical damage.
d. Remote Reset:
1. Do not run high voltage ignition transformer
wires in the same conduit with the Remote Reset
wiring.
2. Do not route Remote Reset wires in conduit
with line voltage circuits.
NOTE: A 13 Vdc power supply must be used any time more
than one Keyboard Display Module is used.
7. Maximum wire lengths:
a. CB780/CB784 leadwires—The maximum length
of leadwire is 300 feet to terminal inputs (Control,
Preignition Interlock, Running/Lockout Interlock,
High Fire Switch and Low Fire Switch).
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 to a Remote Reset pushbutton.
d. Control Bus—The maximum Control Bus cable
length depends on the number of system modules
connected, the noise conditions and the cable used.
The maximum length of all interconnecting wire
is 1000 feet.
8. Make sure loads do not exceed the terminal ratings.
Refer to the label on the CB780/CB784 or to the ratings in
Specifications; see Table 1.
9. Check the power supply circuit. The voltage and fre-
quency tolerance must match those of the CB780/CB784. A
separate power supply circuit may be required for the
CB780/CB784. Add the required disconnect means and
overload protection.
10. Check all wiring circuits and complete the Static
Checkout, see Table 8, before installing the CB780/CB784
on the subbase.
11. Install all electrical connectors.
12. Restore power to the panel.
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