Honeywell 7800 SERIES Installation Instructions Manual page 4

RM7838A 7800 SERIES RELAY MODULES
5. For recommended wire size and type, see Table 1.
6. For recommended grounding practices, see Table 2.
7. For keyboard display module (KDM). The KDM is
powered from a low voltage, energy-limited source.
It can be mounted outside of a control panel if it is
protected from mechanical damage.
NOTE: A 13 Vdc power supply must be used any
time more than one keyboard display
module is used. A maximum of two
keyboard display modules, Data ControlBus
Modules™ or S7810B Multi-Drop Switch
Modules are allowed in any combination.
8. Maximum wire lengths:
a. RM7838A leadwires: The maximum leadwire
length is 300 feet (91 meters) to terminal inputs
(Control, Running 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.
Application
Line voltage terminals
Keyboard Display Module
Data ControlBus Module™
Remote Reset Module
Comunications Interface
ControlBus™ Module
13 Vdc full wave rectified
transformer power input.
Ground type
Earth ground (subbase and relay module).
Signal ground (Keyboard Display Module,
Data Controlbus Module™, Communications
Interface ControlBus™ Module).
66-1087—2
Table 1. Recommended Wire Size and Part Numbers.
Recommended Wire Size
14, 16, or 18 AWG copper conductor,
600 volt insulation wire.
22 AWG two-wire twisted pair with ground,
or five-wire.
22 AWG two-wire twisted pair with ground,
or five-wire.
22 AWG two-wire twisted pair, insulated for
low voltage.
22 AWG two-wire twisted pair with ground.
18 AWG wire insulated for votlages 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 20A 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 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.
Use the shield of the signal wire to ground the device to the signal
gorund terminals [3(c)] of each device. Connect the shield at both ends
of the daisy chain to earth ground.
c. Remote reset leadwires: The maximum length of
wire is 1000 feet (305 meters) to a remote reset
pushbutton.
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).
9. Be sure loads do not exceed the terminal ratings. Refer
to the label on the RM7838A or to the terminal ratings
in Table 3.
10. The keyboard display module, 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
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 (30.5m).
Recommended Part Numbers
TTW60C, THW75C, THHN90C
Belden 8723 shielded cable or equivalent.
Belden 8723 shielded cable or equivalent.
—
Belden 8723 shielded cable or equivalent.
TTW60C, THW75C, THHN90C
Recommended Practice
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