the requirement to vent any hydrogen gas that may be expelled
from the UPS batteries. In addition, the climate control system
has to be powered from the utility. When utility power is lost, the
UPS must be rated to survive elevated temperatures that develop
inside the enclosure, especially when long runtime battery banks
This new class of UPS has to support being installed in locations
where dew point and condensation are an issue. Some manufacturers offer optional conformal coating of the UPS’s internal circuit
boards and components. Conformal coating is applied on the fully
assembled circuit boards and coats the entire board and components, providing a protective barrier from the effects of condensation and conductive dust. In addition, most computer-grade UPS
models have a metal chassis manufactured from pre-plated steel.
During the forming process, the steel is cut to specifications and
formed. The resulting chassis has steel edges that are devoid of
protective plating, and it will rapidly rust if used in outdoor locations, or in a NEMA 3 enclosure deployed outdoors. Manufacturers
offering the new class of industrial UPS models have solved this
problem by plating the chassis steel after it has been formed, or by
fully powder coating the entire chassis and any other metal parts
used in the construction.
Heat is the great destroyer of computer-grade UPS batteries.
Most UPS batteries have a stated operational life based on the
batteries being used in a 77ºF environment. The same batteries used in a 122ºF environment have a service life of less than nine
months. Manufacturers of the rugged UPS addressed this prob-
lem using alternate high temperature batteries. Some have a four
year rated service life at 122ºF. Other types are available with an
operational temperature rating of up to 176ºF. These batteries will
go where others can’t.
As stated previously, some UPS manufacturers are offering
turnkey UPS systems pre-packaged inside NEMA 3 or NEMA 4-
rated enclosures. All of the guesswork has been eliminated since
the internal enclosure cooling, heat loading, and the required
climate controls have been engineered by the UPS manufacturer.
The systems are simply installed, hardwired, and ready-to-go.
UPS is often required to be installed inside of an industrial control panel. Equipment installed inside an industrial control panel
must have a UL508 listing or equivalent. A few manufacturers
of the new class of industrial UPS models have submitted their
models to UL or ETL and have received UL508 designation.
Unfortunately, very few manufacturers have UPSs that have
met this UL specification. This is a problem because many code
inspectors require UPS units to be removed from the industrial
control panel after they have been installed onsite. The inspector
often requires the UPS to be moved to a protected environment
and hardwired to the control panel, and this can be costly.
When installing a UPS in a harsh environment, all of the environmental conditions must be assessed, and only a UPS that has
been designed for that environment should be used. Installing an
off-the-shelf computer-grade UPS in an environment that is outside its rated operational limits is a costly mistake. ECN
NEMA-rated enclosure designed for harsh environments