TM 9-6115-730-24
0003
DC POWER DISTRIBUTION (FIGURE FO-1, SHEETS 2 AND 3) - Continued
Alarm Module A2
The alarm module monitors three conditions: Low Fuel, Overload (current), and Short Circuit (OL/SC). The Low
Fuel condition is monitored by fuel level switch FL1 in the fuel tank and a set of contacts close when the fuel tank
is almost empty. This lights a red lamp on the alarm panel and sounds the alarm buzzer. The lamp will flash at
two cycles per second. Pressing the Alarm Silence button on the alarm module will silence the buzzer. This Low
Fuel signal is also connected to the GSC at P7-23 (SP-1 input) to notify the GSC that the fuel tank is almost empty.
The OL/SC module monitors the Overload and Short Circuit conditions. (The AC Power Distribution discussion
describes the module functions.) A set of relay contacts for each condition is input to this panel and each lights a
yellow lamp. These conditions do not sound the buzzer. There is a relay coil (AR) connected to the LAMP TEST
input/output of the alarm panel. When the LAMP TEST button on the panel is pressed, this relay is energized. The
contacts (FO-1, sheet 2) remove power from the OL/SC module when the relay is energized. This resets the
output relays and any condition sensed by this module. Power for this module is on pins 1 and 7.
Dead Bus Hi/Lo Inputs
Spare input SP-4 at P7-29 is connected to ground through a set of contacts on Dead Bus High (DBHI) and a set of
contacts on Dead Bus Low (DBLO). If there is no voltage on the load bus, DBLO and DBHI will both be de-
energized and the contacts used here will both be closed, grounding P7-29. This input is monitored to verify the
condition of the load bus. A ground here indicates that there is no voltage on the load bus. This input is compared
against the AC voltage monitored at P7-17 and P7-18. If both signals indicate a dead bus, the AUTO mode will
close the load contactor onto the dead bus automatically.
BATTLE SHORT Switch (BSS) Input to ECM
One set of contacts on the BSS is connected to the ECM. This is to notify the ECM when the system is in the Battle
Short Mode. In this mode, shutdown conditions are locked out except for Short Circuit Over Speed.
Auxiliary Fuel Pump Circuit
The AUX FUEL switch on the control panel is labeled AFPS (Auxiliary Fuel Pump Switch) on the schematic. The
ON position is when terminal 1 and 2 are connected together. The OFF position is when terminals 2 and 3 are
connected together. When the AUX FUEL switch is ON, fuel level sensors FL2A and FL2B in the fuel tank control
the Auxiliary Fuel Pump Relay (AFPR). When the fuel level in the tank gets low, FL2A and FL2B will be closed,
applying power to relay AFPR. One set of contacts on AFPR latch, keeping AFPR energized. Another set of
contacts on AFPR apply 24 Vdc to the auxiliary fuel pump. The auxiliary fuel pump will transfer fuel from an
external tank to fill the internal tank in the generator set. As the fuel level rises in the tank, FL2B will open. The
pump will continue transferring fuel since a set of contacts on AFPR latches the relay to the ON condition. When
the fuel level gets to FL2A, those contacts will open. AFPR will drop out and the transfer pump will stop.
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