Sometimes APs are located in areas where they are subject to extreme
moisture, temperatures, dust, and particles. These APs may need to be mounted
inside a sealed enclosure. The National Electronics Manufacturers Association
(NEMA) has a rating system for these enclosures, which are generally referred
to as NEMA enclosures
. The ratings are
shown in Figure
.
The NEMA enclosures most often used for wireless networking products are
Type 2, Type 4, and Type 4X. Some situations might require Type 12 or 13. These
types of enclosures can be purchased through local hardware and electrical
supply stores. Unfortunately, when purchased through these types of supply
stores, the NEMA enclosure is not much more than a sealed box. There are no
external antenna connectors, no external network connectors, no internal
mounting standoffs, and no internal power supply.
Very few NEMA enclosures are available from supply stores with an internal
power supply. Mounting an AP inside the enclosure can be accomplished the same
way as when mounting an AP without an enclosure. Power will have to run to the
enclosure and an electrical workbox installed inside the enclosure. An antenna
mounted inside the box is not very effective, so an external antenna should be
used. In order to attach an external antenna, a bulkhead extender will need to
be installed. This is a simple connector that connects to the AP inside the
enclosure and provides an antenna connector on the outside of the enclosure.
Make sure that any holes drilled into the box are sealed. If even one hole is
left unsealed, then the integrity of the enclosure will be compromised. Antenna
connectors should be mounted to the bottom of the enclosure to provide as much
protection from dripping condensation as possible. It is also a good idea to
seal the antenna connection with a product such as Coax Seal.
Prefabricated NEMA enclosures with antenna connectors, standoff brackets,
and surge protectors are available from third parties. They are more expensive
than a standard NEMA enclosure, but provide better protection for the AP and
can save the SE, the customer, and the installer a great deal of time and
trouble. Special NEMA enclosures are also available that are temperature
controlled and use solar panels to power the equipment. Make sure that the NEMA
enclosure is securely mounted. A NEMA enclosure that measures 0.2 cubic meters
(2 cubic feet) can weigh as much as 13.6 kg (30 lbs). If the enclosure is not
properly secured it could fall, injuring someone, damaging equipment, or
destroying the connected conduit for the power. Exposed wiring creates a
potential fire hazard.