Switchgear or power distribution buildings in hazardous (classified) locations must be provided with positive pressurization so as to prevent the entrance and possible ignition of flammable gases or vapors. North America and many parts of the world adhere to the National Fire Protection Association's NFPA 496 Standard for Purged and Pressurized Enclosures for Electrical Equipment.

Air conditioning systems for remote instrument enclosures (RIE) are similar to switchgear buildings and often require chemical filtration to be incorporated into the system.

Application 1:
A redundant air conditioning system with fire dampers was specified to provide cooling, heating, and slight positive pressure for a switchgear building.

The use of multiple wall mount air conditioners provided the capacity and redundancy required. The control panel provided staging and automatic changeover of first and second stages every seven days.

Prior to delivery to the customer, fire dampers were installed on the supply and return air openings and the actuators were weatherproofed.

Features included copper tube/copper-finned coils, full corrosion coatings, and lifting eyes for ease of installation.

Application 2:
The customer required a fully redundant air conditioning system and slight positive pressure in a corrosive environment. Limited wall space was available.

Two 10-ton wall mount air conditioners were used in conjunction with a chemical filtration unit to remove corrosive gas concentrations while providing a positive pressure to the building interior. Changeover from the active air conditioner to the standby unit was done automatically every seven days.

All three units were constructed of stainless steel with corrosion coatings on coils and tubing.

Application 3:
A large switchgear building was located on a second story level and required 27 tons of cooling. 100% redundancy of the air conditioning system was required and with limited space available.

An explosion-proof split-system air conditioning system was designed with a dual air-handling unit located on the second story level and ducted to the building. The explosion-proof air-handling unit was divided into two separate 27-ton systems, each with blower and evaporator coil sections.

27-ton explosion-proof condensing units were located at grade and refrigerant tubing line sets were run to the air-handling unit.

Application 4:
This application required a large capacity air conditioning system on a very narrow RIE building going into an unclassified location.   A marshalling cabinet was installed along one long interior wall, so the location of the return air grilles had to be considered.  In addition, full redundancy was required of the air conditioning system. 

To satisfy this requirement, two model WCAG120-436, 10 ton wall mount air conditioners were assembled together on a common base to form a small footprint.  A sealing strip was placed between the two units to unitize them.  The compressors were installed on exterior sides opposite from each other to insure full serviceability.

A temperature control panel was installed inside the building and included a seven day timer for alternate running of the air conditioners.   

Shipping was made easier with the air conditioners secured to one end.