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 transformer
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
ignition 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
terminal 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 follows:
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 .
IM 684-6 • ROOFTOP SYSTEMS 24 www .DaikinApplied .com
Maintenance
