Specifications

IM 685-2 21
Operation
Initiate Period: When the relay module is powered it goes
through a 10 second “Initiate” period. It will also enter into
the “Initiate” period if electrical power problems such as low
voltage or momentary interruption occur while the unit is
operating. Operation of the burner fan motor is delayed
throughout the “Initiate” period.
Standby: After the initiate period is completed, the module
will enter the standby mode and await a call for heat by the
temperature control system.
Normal Start-Up
Prepurge: Upon a call for heat the prepurge period will
begin. If the air switch does not detect fan operation within 10
seconds into the prepurge, a recycle to the beginning of the
prepurge will occur.
Ignition Trial: The pilot gas valve and the ignition trans-
former are powered for 10 seconds following the prepurge.
Pilot flame must be proven at the end of that 10 second period
or a shutdown will occur.
Run: If Pilot flame is proven at the end of the 10 second igni-
tion trial. the main gas valve will be powered. If a flameout
occurs, the module will recycle within 3 seconds, and initiate
a new prepurge period. If pilot flame continues to be detected,
the module will be in Run until the power is interrupted to ter-
minal 6, indicating that the temperature control system no
longer requires heat, or that the high limit or another control
has opened.
LED Display
There are five labeled LED's located on the front of the
RM7897A which are energized to indicate operation as fol-
lows:
POWER The RM7897A is powered.
PILOT The prepurge period is complete and the terminal for
the pilot gas valve is powered.
FLAME Pilot flame is detected.
MAIN The ignition trial period is complete, flame is
detected, and the terminal for the main gas valve is powered.
ALARM The RM7897A is on equipment protection lockout.