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 TM 55-1925-273-10-1
OPERATOR'S MANUAL
INLAND AND COASTAL LARGE TUG (LT)
THEORY OF OPERATION
HEATING, VENTILATION, AND AIR CONDITIONING (HVAC) SYSTEMS
GENERAL
The Heating, Ventilation, and Air Condition system (HVAC) supplies the Large Tug (LT) with controlled heat and conditioned
air. The HVAC system also controls the exhaust and vented air circulation in appointed areas on the vessel (figures 1, 2, 3, and 4).
Major components of the HVAC system include the following:
DUCT HEATERS
Duct heaters are flange mounted electric heaters installed in ducting. These heaters are referred to as preheaters or reheaters
depending on their application.
PREHEATER
The preheater heats outside air before distribution.
REHEATER
The reheater ensures that air supplied to a compartment is at the proper temperature.
CONVECTION HEATER
The convection heaters are convection type electric space heaters. They are used in the laundry spaces and sanitary spaces.
SPACE HEATERS
The space heaters are forced air electric space heaters. The space heaters are used in machinery spaces, laundry spaces, and
the bow thruster compartment and towing gear locker.
NATURAL SUPPLY AND EXHAUST VENTS
Natural supply vents are provided in the towing gear locker, emergency generator room, and bow thruster compartment.
Exhaust vents are provided in AMS 1 and AMS 2.
VENTILATION FANS
All ventilation fans are vaneaxial direct drive, with electric motors that provide forced air ventilation. The galley supply fan,
galley ventilator hood exhaust fan, sanitary space exhaust fans, and workshop exhaust fan are single speed fans. All other
workspace fans are 2-speed fans.
FAN COIL UNITS
Fan coil units contain a coil for cooling (air conditioning); a preheater (for heating the spaces); and a single speed electric
motor, belt-driven centrifugal fan. Two horizontal fan coil units are provided on the LT. One unit serves the main deck
spaces, the other serves the 01 level and above.
EOS AIR CONDITIONER
The EOS air conditioner supplies heated or cooled air. An integral fan provides forced air.
AIR CONDITIONING CONDENSER UNITS
The vessel's two fan coil units are supplied with refrigerant by two condensing units located in AMS 2. Each condensing unit
has a capacity of 14. 6 tons of refrigeration under normal operating conditions. Controls are provided for automatic opera-
tion and capacity variation for light loads. Refer to WP 0038 00 for condensing unit details.
0037 00-1
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