If the OUTLET ASSEMBLY circuit breaker A4CB10 on the Rear Control Panel is set to ON position
and POWER MODE switch is set for INT, 115 VAC is continuously applied to connectors A10J1
through A10J4 on receptacle panel.
Re-circulation fan circuit control relay A4K6 is energized under NBC conditions when NBC
switch is pressed or chemical sensor connected to A9J1 senses contaminants and causes
chemical sense relay A4K7 to energize.
Connectors A10J5 and A10J6 are reserved for the NBC re-circulation fans positioned inside
ABS during static operation. They will only receive 115 VAC when re-circulation fan circuit
control relay A4K6 in the Rear Control Panel is energized. Conditions to energize relay
A4K6 include 24 VDC on the 24 VDC bus, circuit breaker A4CB3 closed, MISSION
PROFILE switch A4S8 positioned to STATIC, and NBC FAN switch A4S15/16 positioned to
NBC ("ON"). These are the same conditions required to manually select NBC mode using
INT power. If A4S15/16 is positioned to non-NBC ("OFF") position, relay A4K6 may be
automatically energized by the Chemical Sensor if one is connected to LMS at A9J1 and it
senses a contaminate.
If an external Chemical Sensor is connected to the LMS and it senses a contaminate, it energizes
CHEMICAL SENSOR relay A4K7 which automatically energizes A4K6 and triggers the CBPS system into
NBC mode. Relay A4K7 locks itself energized with 24 VDC from normally closed contacts of CHEM
SENSOR switch A4S7 through its own contacts B1 and B2. Relay A4K7 can be de-energized by pressing
and releasing A4S7, temporarily opening the lock-up circuit keeping A4K7 energized.
When operating the CBPS using internal power, the electric heaters are not used unless they are powered
with 208 VAC, three phase from the TQG. The ECV does not have a 208 VAC, three phase output nor does
it have the facility to develop 208 VAC, three phase from 24 VDC. On internal power, the CBPS uses heated
hydraulic fluid to provide heat for the LMS and ABS. Relay A4K10 energizes and de-energizes to cycle the
hydraulic heat function "ON" and "OFF" as required by the temperature control circuit.
+24 VDC is normally applied to ESS MODE switch A4S17-A pin 11 (common) when A4CB1 is closed. When
positioned to HEAT the 24 VDC is routed from A4S17-A pin 12 to POWER MODE selector A4S1-B pin 3. If
A4S17-A is positioned to INT the 24 VDC continues on to A4TB2 pin 2 and then to A4K10-X1, positive side
of the relay coil. A4K10-X2, the negative side of coil is connected to A4TCU, temperature control unit.
A4TCU electrically connects/disconnects ground to A4K10. A thermistor A1RT1 is attached to air input side
of the recirculation fan senses actual air temperature inside the LMS and ABS as it circulates. Its
resistance varies with air temperature and is sent back to A4TCU. The temperature control unit compares
thermistor output with output of heat control A4R1 or A18R1. A4R1 on the Rear Control Panel and A18R1
on the Control Box Assembly provide CBPS users a way to adjust air temperature inside the LMS and ABS.
A4K18 is de-energized during static mode of operation and connects A4R1 to Temperature Control Unit.
A4K18 is energized during mobile mode of operation and connects A18R1 to A1RT1 Temperature Control
Unit. When actual air temperature measured by thermistor goes below desired temperature set by A4R1
during static operation, A4TCU connects A4K10-X2 to ground energizing A4K10. Contacts B1 and B2 of
A4K10 close to reposition (close) A1SV7 in the hydraulic manifold. Closing A1SV7 blocks the normal
hydraulic fluid return path back to the reservoir and forces the fluid at high pressure over Relief Valve RD2.
As pressure drops to nearly zero, hydraulic fluid temperature rises. From RD2 the fluid is routed to heater
core located in recirculation air stream on its way back to the reservoir. The heat is extracted at heater core
and serves to warm the air recirculated back to the LMS and ABS. As actual air temperature increases
higher than the desired, the Temperature Control Unit disconnects ground from A4K10 which opens normal
fluid return path to reservoir disabling the heat function.