604 ANNUAL KEPOET SMITHSONIAN INSTITUTION, 19 3 



The placing of the fans is varied to suit the local conditions in the 

 individual buildings. Generally, the exhaust ducts are at the corners 

 of the buildings and suj^ply ducts are in the central portion. Con- 

 sequently the compartments containing the exhaust fans are located 

 near the corners under the exhaust stacks, leaving the central por- 

 tions of the fan floors free for intake fans, and the central section of 

 each outer wall for the air intakes. The intakes are made sufficiently 

 large to give low velocities through the louvres. 



The louvre blades are made of heavy wire glass to give light to the 

 interior of the buildings as they take up most of the space otherwise 

 available for windows. Heavy bronze screens protect them and also 

 serve to keep out birds. 



The arrangement whereby fresh air is drawn in through louvres 

 high up on the sides of the buildings and exhaust air is forced out 

 through stacks which extend 20 feet above the roof insures a complete 

 separation of fresh and vitiated air. 



The intake fans and their motors are situated in the open portions 

 of the fan floors where they are accessible. The exhaust fans are, of 

 necessity, inside of chambers at the top of the ducts. Their motors, 

 however, are out on the main floor, the drive shafts being run in to 

 the fans through close-fitting collars in the side plates of the duct. 

 Access to the fans is provided through air locks equipped with air- 

 tight doors which can be opened against the unequal pressure by 

 wedge latches which force the doors open sufficiently to break the 

 seal. 



Each duct is equipped with a damper which may be closed when 

 the fan is shut down so that air from the other fans will not be short- 

 circuited through the idle fan. These dampers are motor operated 

 from the control room and are equipped with limit switches. 



An unusually flexible system of power supply has been worked 

 out based on the facts that all the motors are in groups of three, also 

 that the maximum power equipments are less than the capacity of 

 the minimum size power cables installed by the local companies. 

 Three cables from the New York side and three from the New Jersey 

 side are run to the bus bars in each ventilating building, thus giving 

 one motor in each set a separate cable connection to power supply on 

 each side of the river. Interconnection at the bus bars makes it pos- 

 sible to cut in any or all motors on each cable. Thus connected, each 

 motor may be supplied with power by six independent cables, each 

 capable of carrying the entire tunnel load ; and, as there are at least 

 two independent sources of power at each end of the tunnel, con- 

 tinuity of power supply is absolutely assured. 



As the transformers are located in the ventilating buildings where 

 smoke from an oil fire might be drawn into the ventilating system, 

 air-cooled instead of oil-cooled transformers are used. 



