Specifications

Issue 6 February 2007 417
CMC1 UPS
The uninterruptible power supply (UPS) provides surge protection for all connected cabinets.
Connect the UPS to an electrical outlet that can handle the power requirements of all cabinets.
To calculate the number of amps drawn, use the following formulas.
● For 100 VAC to 200 VAC, multiply 3.5 A times the number of cabinets.
● For 200 VAC to 240 VAC, multiply 1.8 A times the number of cabinets.
Cabinet A (control carrier) is always connected to an unswitched or always on electrical outlet
on the UPS.
Cabinet cooling fans
CMC1 fan unit
Two variable-speed fans are at the bottom of the cabinet. The fans receive +8 VDC to +14 VDC
from the power supply. An air filter, which can be removed and cleaned or replaced, is located
above the fans. Outside air flows into the bottom of the cabinet. It then flows around the circuit
packs, and out through the top of the cabinet.
If the cabinet temperature reaches 158
o
F (70
o
C), the temperature sensor in the power supply
shuts the system down and invokes the emergency transfer.
MCC1 fans
A fan unit that consists of six fans is mounted near the center of the cabinet. The three front fans
blow up, and the three rear fans blow down. A removable air filter is provided on top and below
each fan unit. Four sensors monitor the cabinet temperature. Three sensors are inside the
cabinet top and one sensor is inside the cabinet bottom. One of the top sensors affects the
speed of the front fans and the bottom sensor affects the speed of the rear fans. A speed control
and thermal alarm circuit in each fan monitors the sensors. When a sensor indicates a change
in cabinet temperature, the circuit in a fan changes the speed for that fan.
A power cable from the power-distribution unit connects
● -48 VDC to each fan,
● +5 VDC to the speed control and thermal alarm circuit in each fan, and
● temperature sensor signals to the equivalent circuit in each fan.
One pair of wires is routed to each fan circuit. A minor alarm is triggered if the speed of any fan
drops below minimum. The minor alarms are sent to the processor circuit pack in the PPN
cabinet and to the maintenance circuit pack in an EPN cabinet. Alarm signals are also routed to
the equivalent circuit in each fan. One pair of wires is routed to each fan circuit.
A minor alarm occurs if a fan stops because of a loss of -48 VDC. One of the cabinet top
thermal sensors sends an alarm if the exhaust temperature reaches 149
o
F (65
o
C).
Another cabinet top sensor senses if the exhaust temperature reaches 158
o
F (70
o
C). If the
temperature reaches 158
o
F the system shuts down, and the Emergency Transfer is invoked.