Checkout; Communication Interface Controlbus Module - Honeywell 7800 Series Manual

chain configuration string may require a 120 ohm
(1/4 watt minimum) resistor termination across
terminals 1 and 2 of the electrical connectors, see
Figs. 11 and 12.
d. Remote Reset—Use no. 22 or greater twisted pair
wire, insulated for low voltage, see Figs. 11 and 12.
e. Communication Interface ControlBus Module—
For communications purposes, use an unshielded
3-wire twisted cable if the leadwire run and noise
conditions permit or use a Belden 8771 shielded
cable or equivalent. The Keyboard Display Mod-
ule, DATA CONTROLBUS MODULE (for remote
mounting or communications) or Communication
Interface ControlBus Module 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 de-
vices listed above is not important. Be aware that
modules on the closest and farthest end of the daisy
chain configuration string may require a 120 ohm
(1/4 watt minimum) resistor termination across
terminals 1 and 2 of the electrical connectors, see
Figs. 11 and 12.
5. Recommended grounding practices:
a. The earth ground provides for a connection be-
tween the subbase and the control panel or the
equipment. The earth ground wire must be capable
of conducting the current to blow the 20A fuse (or
breaker) in event of an internal short circuit. The
RM7838B needs a low impedance ground connec-
tion to the equipment frame which, in turn, needs a
low impedance connection to earth ground. For a
ground path to be low impedance at RF frequencies,
the connection must be made with minimum length
conductors that have a maximum surface area. Wide
straps or brackets are preferred rather than leadwires.
Be careful to ensure that mechanically tightened
joints along the ground path, such as pipe or conduit
threads or surfaces held together with fasteners, are
free of nonconductive coatings and are protected
against corrosion on mating surfaces.
b. Keyboard Display Module, DATA CONTROL-
BUS MODULE™ or Communication Interface
ControlBus Module—The shield, if used, should
be connected to the signal ground terminal 3(c)
provided as part of the 7800 SERIES device
ControlBus connection. Connect the shield at both
ends to earth ground.
c. Each RM7838B will have an earth ground termi-
nal that must be grounded to the metal control panel
with wire as short as practical. Each ground wire
must be capable of carrying a fault current equal to
the rating of the protective fuse (20A). A number
14 copper conductor is adequate, but wide straps
or brackets are preferred 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-
tor wiring.
2. Do not route flame detector wires in conduit
with line voltage circuits.
3. Enclose the flame detector wires without armor
cable in metal cable or conduit.
4. Follow directions in flame detector Instructions.
b. DATA CONTROLBUS MODULE™:
1. Do not run high voltage ignition transformer
wires in the same conduit or close proximity
with the DATA CONTROLBUS MODULE
wiring.
2. Do not route DATA CONTROLBUS MOD-
ULE wires in conduit with line voltage circuits.
c. Keyboard Display Module (VFD):
1. Because the VFD is powered from a low volt-
age, energy limited source, it can be mounted
outside of a control panel, without special wiring
procedures, 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 the Remote Reset wires in conduit
with line voltage circuits.
7. Maximum wire lengths:
a. The maximum length of leadwire is 300 feet to the
terminal inputs (Control, Preignition Interlock, Run-
ning/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. DATA CONTROLBUS MODULE—The maxi-
mum 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 interconnecting wire is
1000 feet.
8. Make sure loads do not exceed the terminal ratings.
Refer to the label on the RM7838B or to the ratings in Speci-
fications, see Table 1.
9. Check power supply circuit. The voltage and frequency
tolerance must match those of the RM7838B. A separate
power supply circuit may be required for the RM7838B. Add
the required disconnect means and overload protection.
10. Check all wiring circuits and complete the Static
Checkout, see Table 7, before installing the RM7838B on the
subbase.
11. Install all electrical connectors.
12. Restore power to the panel.
15
RM7838B
INSTALLATION
65-0120—1