Assembly - Honeywell 7800 Series Installation Instructions Manual

d. Remote Reset—Use 22 AWG or greater twisted
pair wire, insulated for low voltage.
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
15A fast blow 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
connection to earth ground. For a ground path to
be low impedance at RF frequencies, the connec-
tion must be made with minimum length con-
ductors that have a maximum surface area. Wide
straps or brackets are preferred rather than lead-
wires. Make sure 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 mating surface corro-
sion.
b. Keyboard Display Module, DATA CONTROLBUS
MODULE™ or Modbus 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. The
shield should be connected at both ends to
ground.
c. RM7888A—Each RM7888A will have an earth
ground terminal that must be grounded to the
metal control panel with wire as short as practi-
cal. Each ground wire must be capable of carry-
ing a fault current equal to the rating of the
protective fuse 15A fast blow. A 14 AWG copper
conductor is adequate, but wide straps or brack-
ets are preferred to leadwires.
6. Recommended wire routing:
a. Flame detector leadwires:
(1) Do not run high voltage ignition transformer
wires in the same conduit with flame detec-
tion wiring.
(2) Do not route scanner wires in a conduit with
line voltage circuits.
(3) Enclose scanner wires without armor cable in
metal cable or conduit.
(4) Follow directions given in flame detector
instructions.
b. DATA CONTROLBUS MODULE™ or Modbus
Module:
(1) Do not run high voltage ignition transformer
wires in the same conduit or in close proxim-
ity to the MODULE wiring.
(2) Do not route MODULE wires in conduit with
line voltage circuits.
c. Keyboard Display Module:
(1) Because the VFD is powered from a low volt-
age, energy limited source, mount it outside a
control panel, without using 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 Remote Reset wires in the same
conduit with line voltage circuits.
RM7888A 7800 SERIES RELAY MODULE
7. Maximum wire lengths:
a. For the flame detector leadwires, the maximum
flame sensor leadwire length is limited by the
flame signal strength.
b. For the Remote Reset leadwires, the maximum
length of wire is 1000 feet to a Remote Reset
pushbutton.
c. For the DATA CONTROLBUS or MODBUS MOD-
ULE™, the maximum cable length depends on
the number of system modules connected, the
noise conditions and the cable used. The maxi-
mum length of all interconnecting wire is 1000
feet [305 meters].
8. Make sure loads do not exceed the terminal ratings.
Refer to the label on the RM7888A or to the ratings
in the specifications; see Table 1.
9. Check the power supply circuit. The voltage and fre-
quency tolerance must match those of the
RM7888A. A separate power supply circuit may be
required for the RM7888A with the required discon-
nect means and overload protection added.
10. Check all wiring circuits and complete the Static
Checkout before installing the RM7888A on the sub-
base: see Table 10.
11. Install all electrical connectors.
12. Restore power to the panel.

ASSEMBLY

Mounting the RM7888A
NOTE: For installation dimensions, see Figs. 1
Relay Module Mounting
(Figs. 12 and 13)
1. Mount RM7888A vertically, see Figs. 12 or 13, or
mount horizontally with the knife blade terminals
pointing downward. When mounted on the Q7800A,
the RM7888A must be in an electrical enclosure.
2. Select the location in the electrical enclosure. Be
sure to allow adequate clearance for servicing,
installation and removal of the RM7888A, Keyboard
Display Module, flame amplifier, flame amplifier sig-
nal voltage probes, electrical signal voltage probes
and electrical connections.
a. Allow an additional two inches below the
RM7888A for the flame amplifier mounting.
b. Allow an optional three-inch minimum to both
sides of the RM7888A for electrical signal volt-
age probes.
3. Make sure no subbase wiring is projecting beyond
the terminal blocks. Tuck in wiring against the back
of the subbase so it does not interfere with the knife
blade terminals or bifurcated contacts.
IMPORTANT:
The RM7888A must be installed with a plug-in
motion rather than a hinge action.
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