User's Manual

Ripwave Base Station I&C Guide Navini Networks, Inc.
202 Part #40-00047-00 Rev D v1.0
February 28, 2003
Air Conditioner(s)
Air conditioners provide active cooling to equipment in the outdoor cabinet and are normally
used on cabinets where thermoelectric coolers, multiple air insulated walls, Air to Air Heat
Exchangers, and Forced Air cooling do not provide adequate capability to maintain internal
cabinet air temperatures within acceptable ranges for installed equipment. Air conditioners may
be equipped with economizers to reduce operating costs, as well as heat strips, to prevent ice
formation on the evaporator coils, and heat to the interior of the cabinet. The use of air
conditioners requires careful consideration of airflow within the interior of the cabinet, to ensure
that adequate cooling is provided to all equipment in the cabinet and that hot spots are not
created.
Sizing
Air conditioners should be sized to provide for an optimal duty cycle and reserve cooling
capacity. A high duty cycle will typically lead to early failure of the air conditioner, since air
conditioners are not normally intended to have an extremely high duty cycle. Significant over-
sizing of an air conditioner will lead to inefficient operation and greater initial air conditioner
and cabinet costs required to support the larger air conditioner.
Consideration should be given to providing a percentage of reserve capacity to allow for
additions to the installed equipment, increases in power requirements of installed equipment, and
loss of efficiency of the air conditioner due to age or leakage of refrigerant over time. Reserve
capacity is likely to be reflected in a reduced duty cycle for the installed air conditioner.
Advantages
Air conditioners can be sized to support thermal loads in excess of those that can be managed
with other active and passive cooling techniques. Additionally, internal cabinet temperatures and
humidity levels can be maintained at consistent levels, which may contribute to greater
equipment stability and longevity.
Disadvantages
The loss of commercial power to an outdoor cabinet equipped with an air conditioner and a
backup power system may not prevent the site from failing, even if adequate backup power
exists to power the equipment installed in the cabinet for the duration of the power outage, due to
the inability of the backup power system to operate the air conditioner. Without the air
conditioner removing waste heat generated by the equipment installed in the cabinet and by heat
contributed by solar gain, during summer months, the internal air temperature inside the cabinet
may reach a sufficiently high level to cause failure to one or more pieces of installed equipment
within the cabinet, as a result of overheating. Additionally, utility costs and maintenance costs
will be higher for sites with air conditioners installed in an outdoor cabinet.