Specifications

12 IM 685-2
Flame Safeguard
See manufacturer's bulletin for more detailed information on
flame safeguard RM7897A.
The Honeywell RM7897A is a microprocessor based inte-
grated burner control that will perform self-diagnostics, trou-
bleshooting, and status indication, as well as the burner
sequencing and flame supervision.
Keyboard Display Module
The Honeywell S7800A1001 module is an optional device
available for use with the RM7897A. It can be a permanent
accessory added to the RM7897A or it can be carried by the
service technician as a tool that is very easy to mount when
servicing the RM7897A. It mounts directly onto the
RM7897A and has a 2 row by 20 column display. The module
will indicate flame signal dc volts, sequence status, sequence
time, hold status, lockout/alarm status, total hours of opera-
tion, total cycles of operation, and can provide 127 different
diagnostic messages for troubleshooting the system.
The module will give a fault history. It can be mounted to the
RM7897A and will retrieve information on the six most
recent faults.
Consult the Honeywell bulletin 65-0090-1 “7800 Series,
Keyboard Display Module” and 65-0118-1 “7800 Series,
System Annunciation, Diagnostics and Troubleshooting.”
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 in the
first 10 seconds into the prepurge period a recycle to the
beginning of the prepurge will occur.
Ignition Trial: The “start” combination gas control and the
ignition transformer are powered for 10 seconds following
the prepurge. Flame must be proven at the end of that 10 sec-
ond period or safety shutdown will occur.
Run: If flame is proven at the end of the 10 second ignition
trial the “start” combination gas control will remain powered
and on multiple valve units, the other parallel piped main
valves will become powered. If a flameout occurs the mod-
ule will recycle within 3 seconds, and initiate a new prepurge
period. If 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 safety control has opened.
N
C
N
O
L
S
2
C C
N
C
N
O
L
S
1
1
2
3
4
5
6
C1
C2
1
2
3
4
5
6
C1
C2
NB NB
A
IR
S
W.
C
Figure 6c. Typical Burner Control Box
Figure 7. RM7897A Flame Safeguard