MUC IOM
20
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P a g e
Operation - Modes
Fail Mode (Alarm)
The MUC after a 15 second delay will deactivate the green LED, activate the red LED,
activate the alarm buzzer and releases the gas relay into the normally open position if
any or combination of the following occurs:
1. If the fan motor provides <4VDC
2. If the RPM frequency feedback is <150 pulses per seconds (if not by-passed by
jumper)
3. The Prover input is de-energized
The damper relay remains in the closed position during Fail Mode.
The MUC will automatically reset and resumes normal operation once the alarm
condition clears. If the MUC should receive the missing feedback signal while in the
Fail Mode for at least 2 seconds, then the MUC will return to the Run Mode and will
deactivate the red LED and alarm buzzer, activate the green LED and drive the gas
relay to the closed position.
During Fail Mode, an override (Mute/Silence) switch, when depressed will deactivate
the audio buzzer for 2 minutes. After 2 minutes if the MUC is still in Fail Mode, the audio
buzzer will be activated. Muted audio alert mode will flash the red LED with a 50% duty
cycle.
