Honeywell RM7838A User Manual

7800 SERIES RELAY MODULES
5 32-00213—01
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 or
Data ControlBus 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.
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 maxi-
mum 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)
must be wired in a daisy chain configuration, (1(a)-
1(a), 2(b)-2(b), 3(c)-3(c)). The order of interconnec-
tion 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).
Table 1. Recommended Wire Size and Part Numbers
Application
Recommended
Wire Size
Recommended
Part Numbers
Line voltage
terminals
14, 16, or 18 AWG
copper conductor,
600 volt
insulation wire.
TTW60C,
THW75C,
THHN90C
Keyboard Display
Module
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
votlages and
temperatures for
given application.
TTW60C,
THW75C,
THHN90C
Table 2. Recommended Grounding Practices.
Ground Type Recommended Practice
Earth ground (subbase and
relay module).
• 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.
• 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.
• Make sure that
mechanically tightened
joints along the ground
path are free of
nonconductive coatings
and protected against
corrosion on mating
surfaces.
Signal ground (Keyboard
Display Module,
Data Controlbus Module™
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.

Honeywell RM7838A Specifications

General

Brand	Honeywell
Model	RM7838A
Category	Control Unit
Language	English