Birdwell Model BTB-RM Single - Package Explosion Proof Cab Mount Air Conditioners ETL Listed 1-1/2, 2, 2-1/2, 3, 3-1/2, 4, 5, 6, 7-1/2, 10 Tons. Nominal Sizes  These significant features assure ease of installation plus performance and serviceability... ETL certified by Intertek Testing Services to be in compliance with applicable UL and CSA codes and standards for Class I or II, Division I or II hazardous locations (general purpose optional).  Entire unit cabinet constructed of 16 gauge type 304 (type 316 optional) stainless steel for maximum protection from corrosive environments.  Explosion proof full hermetic compressor (Div. 1 units).  Explosion proof evaporator and condenser fan motors (Div. 1 units).  High voltage electrical controls are in one NEMA 7 explosion proof control box.  Low voltage electrical controls are served by an intrinsically safe relay.  Evaporator and condenser coils have copper tubes and aluminum fins. Optional roof curb for quick and inexpensive installation cost. Optional supply-air plenum with air diffuser. Optional Heresite baked phenolic or epoxy coil coatings for corrosion protection. High efficiency compressor has internal pressure relief valves.  Thermostatically control expansion valve.  High and low refrigerant pressure cut-out switches.  Solid state time delay relay to prevent short cycling.  Frost control to stop compressor in the event of coil icing due to dirty filters, etc. Unit is fully serviceable from access panels and external grills.  Service valve with pump-down capability.  Refrigerant sight glass with moisture indicator for aid in servicing system.  Standard low ambient operation to 20°F.  Optional explosion proof electric heat.  Also available in water cooled models.