Nortel DMS-100 Series Maintenance Manual page 106

2-12 OPAC maintenance overview
When the internal temperature drops below 41 F (5 C), four 150-W wall
heaters turn ON.
When the temperature rises above 59 F (15 C), the heaters turn OFF. Low
temperature alarms are activated when cabinet temperatures drop to
32 F (0 C).
Battery gases that generate in the electronics compartment vent through the
roof of the electronics compartment.
Air induction roof
Noncorrosive materials compose the air induction roof. The roof design
contains barriers that do not allow dust, sand, water and pests into the
cabinet. Refer to the following figure.
Two air filters are located behind hinged filter covers. One air filter is on the
front of the roof. One air filter is on the rear of the roof. The filters are
made of open-cell, polyurethane foam.
Fans, heaters and insulation control the interior temperature. Six 6-in., 240,
48 V dc fans that a thermostat controls maintain air circulation and provide
cooling. The six fans are for exhaust purposes. These fans circulate air out
of the cabinet through the equipment side.
The thermostat controls the fans in the roof. The bank of fans turns on when
the temperature inside the electronics compartment measures 65 F (18 C).
High temperature alarms activate when the cabinet temperature reaches
140 F (60 C) at the monitoring point. The fan arrangement and high
temperature sensor location appear in the following figure.
Two cooling units are located under the HIE and RMM shelves. Each
cooling unit contains two fans that run continuously.
Foil-faced, closed cell boards with a minimum insulation value of R8
insulate the air induction roof. A positive temperature differential between
interior cabinet air and outside air controls humidity.
297-8211-550 Standard 05.01 August 1999