-4- 



Grease connections extend through the top of the housing to facilitate 

 servicing from the outside. Beneath the refrigeration coils of each unit 

 is a line to a floor drain. 



On top of the housing for the air -handling units is a variable trans- 

 former (fig. 2) that controls the input to the heaters within. 



The two air-handling units are enclosed in an insulated cabinet of 

 construction similar to that of the main room. Each unit is provided 

 with a separate access panel for readily servicing, and outside air 

 intakes with adjustable dampers. 



The two supply registers are adjustable so that the volume and 

 direction of the circulating air may be controlled. Both the supply 

 register and the return air grille are cadmium-plated to prevent 

 rusting. 



A 400-watt, copper -coated, cable-type electric heater is installed 

 just below the refrigerant coil of each air-handling unit. The heat 

 rises by convection and melts any ice or frost that has accumulated 

 on the coil. 



In the air duct of each unit an auxiliary 9 -watt propeller fan is 

 installed between the blower and the supply register. These fans 

 circulate air in a reverse direction to the usual flow immediately 

 after the defrosting heater has been turned off and before the unit is 

 returned to operation. This reverse flow dries the moisture off the 

 defrosted coils and brings them to room temperature, thereby elimi- 

 nating temperature fluctuation when the unit is put into operation. 



Humidity is supplied to the cabinet by means of steam regulated 

 by pneumatic modulating steam valves (fig. 3) and solenoid valves. 



Control Equipment 



A heavy sheet -metal panel for mounting control instruments and 

 attendant relays and accessories is installed adjacent to the anteroom 

 and facing the front of the cabinet. On this panel are two time -pattern 

 transmitters and two circular chart controller-recorders, one each for 

 temperature and humidity (fig. 5). These instruments operate on 115- 

 volt, 60-cycle current and require compressed air at 30 p.s.i. On the 

 rear of the panel are six pneumatic-electric relay switches for con- 

 trolling solenoid valves in the air-conditioning system, a diverting air 

 relay and a 6:1 pneumatic air relay for controlling the compressor 

 capacity, and a diverting air relay for controlling the opening of a 

 modulating steam valve, as well as the accessory air pipelines, air- 

 reducer valves and drip wells, and electrical connections. 



Two 5-horsepower air compressors, one of them used as an auxil- 

 iary, supply air for the instruments and controls. A calcium chloride 

 drier is located in the cabinet air- supply line. 



