Nortel DMS-100 Series Maintenance Manual page 214

5-12 OPAC hardware
Cooling units
The OPAC has two cooling units under the HIE and RMM shelves. Each
cooling unit contains two fans. These fans are provided in addition to the
fans in the roof assembly. These fans run continuously to circulate air in the
cabinet. The baffle can be removed for maintenance. The baffel must be
installed again because the baffle directs air flow in the cabinet.
Air induction roof option
The air induction roof NTRX61BA-BC controls the OPAC interior
temperature. Fans circulate outside air through the cabinet. The roof keeps
the cabinet free from dust, sand, water, and pests. Two air filters are made
from open-cell, polyurethane foam, and are behind hinged filter covers.
Six six-inch, 240 cfm, 48 V dc fans, controlled by a thermostat, circulate and
cool the air. The fans turn ON at 18 C (65 F). The fans turn OFF when
cabinet temperatures fall below 18 C (65 F), add or subtract 2 C.
Heaters
Electric strip heater pads, are on the walls of the electronics compartment.
The units, are flat elements that provide standard surface heating.
When the internal temperature drops below 5 C (41 F), four 150W wall
heaters turn ON. When the temperature is greater than 15 C (59 F), the
heaters turn OFF.
Insulation
One inch thick foil-faced, closed-cell boards insulate the cabinet.
Use of air filters
The air filters are made from a woven mesh polypropylene or an open cell
foam. The polypropylene or foam is immediately in front of the air intake
and exhaust openings.
The filters, stop dust, sand, water, snow, and pest entry. The filters have a
minimum dust arrestment of 80% and a minimum fire rating of UL Class 2.
Gas vent
Hydrogen battery gas vents in the OPAC through filters on the air induction
roof. The maximum gas increase allowed is 1%.
Humidity control
The system mixes outside humid air with warmer cabinet air to control
humidity.
297-8211-550 Standard 05.01 August 1999