RM7890A,B,C/EC7890A,B 7800 SERIES RELAY MODULES
66-1089—11
4
Table 2. Recommended Grounding Practices.
a
The RM/EC7890 must have an earth ground providing 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 fuse (or breaker) in event of an
internal short circuit. The RM/EC7890 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 connection
must be made with minimum length conductors having maximum surface areas. Wide straps or brackets rather than leadwires
are preferred. Be careful to verify 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 corrosion.
b
2000 VA maximum connected load to the RM/EC7890 Assembly.
c
See Tables 4 and 5 for device load combinations.
d
Requires 220-240 to 120 Vac, 10 Va minimum stepdown transformer to drive the shutter.
Ground Type
Recommended Practice
Earth ground (subbase and relay
module).
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 15A 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 is required, 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.
Signal ground (Keyboard Display
Module, Data ControlBus Module™
Use the shield of the signal wire to ground the device to the signal ground terminals—
3(c)—of each device. Connect the shield at both ends of the daisy chain to earth
ground.
Table 3. Terminal Ratings.
Terminal Number
Description
Ratings (RM7890A,B,C)
Ratings (EC7890A,B)
G
Flame Sensor Ground
—
—
Earth G
Earth Ground
a
—
—
L2(N)
Line Voltage Common
—
—
3
Line Voltage Supply (L1)
120 Vac (+10%/-15%), 50 or
60 Hz (±10%).
b
220-240 Vac (=10%/-15%), 50 or 60 Hz
(±10%).
4
Alarm
120 Vac, 1A pilot duty.
220-240 Vac, 1A pilot duty.
5
Unused
—
—
6
Burner Controller and Limits
120 Vac, 8A run, 43A inrush. 220-240 Vac, 5A (maximum).
7
Unused
—
—
8
Pilot Valve/Ignition.
120 Vac.
c
220-240 Vac, 4A at P.F. = 0.5, 20A inrush.
9
Main Fuel Valve.
120 Vac.
c
220-240 Vac, 4A at P.F. = 0.5, 20A inrush.
10 Ignition
120 Vac, 4.5A ignition.
c
220-240 Vac, 4A at P.F. = 0.2.
F(11)
Flame Sensor
60 to 220 Vac, current limited. 60 to 220 Vac, current limited.
12 to 21
Unused.
—
—
22
Shutter
120 Vac, 0.5A (RM7890B).
220-240 Vac (EC7890B only).
d
maxon.su