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Figure 6c. Typical Burner Control Box
Flame Safeguard
See manufacturer’s bulletin for more detailed information on flame safeguard RM7895A.
The Honeywell RM7895A is a microprocessor based integrated burner control that will perform self-
diagnostics, troubleshooting, 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 RM7895A. It can
be a permanent accessory added to the RM7895A or it can be carried by the service technician as a tool
that is very easy to mount when servicing the RM7895A. It mounts directly onto the RM7895A 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 operation, 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 RM7895A 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 second period or safety
shutdown will occur.
