Honeywell 7800 Series Manual page 14

RM7888A
WIRING
3(c)-3(c)). The order of interconnection of all the
devices is not important. Be aware that modules on
the closest and farthest end of the daisy chain con-
figuration require a 120-ohm (1/4 watt minimum)
resistor termination across terminals 1 and 2 of the
electrical connectors for connections over 100 feet
[30 meters].
d. Remote Reset—Use no. 22 or greater twisted pair
wire, insulated for low voltage.
e. Communication Interface ControlBus Module—For
communications purposes, use an unshielded 3-wire
twisted cable if the leadwire run and noise conditions
permit; however, some installations may need up to
five wires; three for communications and two for
remote reset (either in a single cable or separate cables
for communications or remote reset) or use Belden
8771 shielded cable or equivalent. The Keyboard Dis-
play Module, DATA CONTROLBUS MODULE™
(for remote mounting or communications) or Com-
munications 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 devices is not important. Be aware that modules
on the closes and farthest end of the daisy chain con-
figuration require a 120-ohm (1/4 watt minimum)
resistor termination across terminals 1 and 2 of the
electrical connectors for connections over 100 feet
[30 meters].
Fig. 9—Wiring the Keyboard Display Module
with Communications Interface ControlBus
Module.
S7800 KEYBOARD DISPLAY MODULE
(MOUNTED ON 7800 SERIES RELAY MODULE)
1 2
120
RESISTOR
120
RESISTOR
1 2
1 THREE WIRE SHIELDED CABLE MAY BE REQUIRED. TWO
120 OHM TERMINATING RESISTORS ARE REQUIRED FOR
CONNECTIONS OVER 100 FEET [30 METERS]. CABLE
SHIELD MUST BE TERMINATED TO EARTH GROUND AT
BOTH ENDS. IF SHIELDED CABLE IS NOT USED,
TWISTED PAIR WIRE MUST BE USED.
65-0175
MOMENTARY
PUSH BUTTON
SWITCH
3 4 5
1
1
QS7800
3
COMMUNICATIONS
INTERFACE
CONTROLBUS
MODULE
M1990D
5. Recommended grounding practices:
a. Use earth ground to provide a connection between
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 the
event of an internal short circuit. The RM7888A needs
a low impedance ground connection to the equipment
frame which, in turn, needs a low impedance connec-
tion 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. Make sure that me-
chanically 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 mating surface corrosion.
b. Keyboard Display Module, DATA CONTROLBUS
MODULE™ or Communication Interface Control-
Bus Module—The shield, if used, should be con-
nected to the signal ground terminal 3(c) provided as
part of the 7800 SERIES device ControlBus connec-
tion. The shield should be connected at both ends to
ground.
Fig. 10—Wiring for multiple Keyboard Display
Modules.
S7800 KEYBOARD DISPLAY MODULE
(MOUNTED ON 7800 SERIES RELAY MODULE)
2 3
1
120 Ω
RESISTOR
1
120 Ω
RESISTOR
1
2 3
1
S7800 REMOTE KEYBOARD DISPLAY MODULE
1
THREE WIRE SHIELDED CABLE MAY BE REQUIRED. TWO
120 OHM TERMINATING RESISTORS ARE REQUIRED FOR
CONNECTING OVER 100 FEET [30 METERS]. CABLE SHIELD
MUST BE TERMINATED TO EARTH GROUND AT BOTH ENDS.
IF SHIELDED CABLE IS NOT USED, TWISTED PAIR WIRE
MUST BE USED.
2
WHEN CONNECTING THE KEYBOARD DISPLAY MODULE DATA
CONTROLBUS MODULE™, OR REMOTE RESET MODULE
EXTERNAL FROM THE CONTROL CABINET, APPROPRIATE
MEASURES MUST BE TAKEN TO MEET EN60730 SAFETY
LOW VOLTAGE REQUIREMENTS (SEE APPROVALS).
14
MOMENTARY
PUSH BUTTON
SWITCH
4 5
2
13 Vdc
4 5
POWER SUPPLY
L2
L1
(HOT)
M5006E