User Manual

MCA9129-90-A Installation & Service Manual

044-05060 Rev. C 3-2 July 2001November 2002

3-3.1 27V Indicator (+27VDC)

Green LED. When lit, indicates that the +27Vdc supply is greater than +21Vdc and less than

+30Vdc. The indicator will blink if the voltage is 28Vdc to 30Vdc. If the voltage source drops be-

low +21V a timer is started and the DC fail counter is incremented. After five seconds the voltage

is analyzed, if still faulted the counter is incremented. If the count equals 25 before the timer

reaches 15 minutes, the MCPA will enter fault mode. Fault mode will disable the MCPA. The

+27V indicator will turn off, the DC FAIL and LPA DISAB indicators will illuminate and a summary

fault will occur signaling the shelf that the MCPA is disabled. In fault mode the LED indications

are latched. Toggling the reset switch will enable the MCPA and clear the summary alarm and

latched indicators. If 15 minutes elapse before the counter reaches 25, the counter and timer will

reset to zero. If the DC input voltage exceeds +30 volts, the MCA will be disabled instantane-

ously, as indicated by the illumination of the LPA DISAB indicator. The +27V and DC FAIL indi-

cators will alternatively blink at a 1Hz rate. A timer is started and the DC fail counter is incre-

mented. After five seconds the voltage is measured. If the fault exists the counter is incre-

mented. If the count equals five before the timer reaches 15 minutes, the MCPA will enter fault

mode. The +27V indicator will turn off, the DC FAIL and LPA DISAB indicators will illuminate and

a summary fault will occur signaling the shelf that the MCPA is disabled. Toggling the reset switch

will enable the MCPA and clear the summary alarm and latched indicators. If 15 minutes elapse

before the counter reaches five, the counter and timer will reset to zero.