MUA-SVX01A-EN • Direct-Fired Make-up Air
71
Trouble Shooting
Operation
The RM7895, EC7895 and RM7896 has the operating sequence as shown in
figures 14 and 15. The LED provides positive visual indication of the program
sequence for power, pilot, flame, main and alarm.
Initiate
The relay module enters the initiate sequence when it is powered. The RM7895A/
B/C/D, EC7895A/C and RM7896A/B/C/D can also enter the initiate sequence if the
relay module verifies voltage fluctuations of +10/-15% or frequency fluctuations
of ±10% during any part of the operating sequence. The initiate sequence lasts
for 10-seconds unless the voltage or frequency tolerances are not met. When not
met, a hold condition is initiated and displayed on the optional KDM for at least
five seconds. When met, the initiate sequence restarts. If the condition is not
corrected and the hold condition exists for 4-minutes, the flame relay module
locks out.
Causes for a hold condition in the initiate sequence are as follows:
•
AC line dropout detection.
•
AC line noise that can prevent a sufficient reading of the line voltage inputs.
•
Low line voltage brownouts.
The initiate sequence also delays the burner motor starter from being energized
and de-energized from an intermittent AC line input or control input.
Standby
The flame relay module is ready to start an operating sequence when the
operating control input determines a call for heat is present. The burner switch,
limits, operating limit control and all microcomputer-monitored circuits must be
in the correct state for the relay module to continue into the "prepurge"
sequence.
Normal Start-up Prepurge
The module provides "prepurge" timing selectable from two seconds to thirty
minutes with power applied and the operating control indicating a call for heat.
•
The airflow interlock, burner switch, run/test switch and all microcomputer-
monitored circuits must also be in the correct operating state.
•
The motor output, terminal 4, is powered to start the prepurge sequence.
•
The airflow interlock input closes 10-seconds into prepurge or within the
specified purge card timing. Otherwise, a recycle to the beginning of
prepurge or lockout occurs. This is dependent on how the airflow switch
selectable jumper (JR3) is configured.
Flame Relays
