MIL-PRF-24775A(SH)
TABLE I. Fan-coil unit capacity - Continued. 1/
Notes:
1/
Abbreviations
ft3/min = cubic feet per minute
in. w.g. = inches of water gauge, external static pressure at fan-coil unit discharge (± 5%)
r/min = revolutions per minute
MBH = Btu/h in thousands
Btu/h = British thermal units per hour
EDB = entering dry bulb air temperature
EWB = entering wet bulb air temperature
°F = degrees Fahrenheit
kW = kilowatts
gal/min = gallons per minute, chilled water flow rate
2/
Rated airflow and capacity shall be at design operating conditions, that is, high speed (1800 r/min), air EDB
80 °F, and air EWB 67 °F. Fan motors shall have two speeds. Low speed shall be 1200 r/min.
3/
Cooling capacity and cooling coil sizing shall be based on 45 °F chilled water and a minimum waterside fouling
factor of 0.0005. Cooling capacity shall be the required cooling coil load (MBH), at the specified cooling coil
entering air conditions (EDB, EWB), in the section of the fan-coil unit between the fan discharge and the cooling
coil inlet. This load shall include compartment and replenishment air total heat loads (sensible and latent) and
fan motor sensible heat.
3.11.4 Operation. Fan-coil units shall be constructed for continuous operation unless a low voltage condition, a
temporary loss of voltage, or activation of the manual "stop" pushbutton or switch opens the electrical control
circuitry, turning off the unit.
3.11.5 Physical interface dimensions. To suit interface requirements and equipment interchangeability, the
physical layout of the fan-coil unit shall be limited to Figure 3, the mounting to Figure 4, the duct inlet connection to
3.11.6 Cabinet. The cabinet enclosure shall be of a material equivalent in strength to 0.059 USSGA steel. The
frame or chassis shall be rigid and of adequate strength to support and maintain alignment of the assembled parts.
The cabinet shall be designed to be hard mounted to the ship foundation without the need for external vibration
isolators. All seams shall be sealed to prevent air leakage under normal operating conditions. The cabinet shall
have standard features that permit left- or right-hand assembly of the cooling coil by the installing activity. All
interior material components between the fan outlet and the heater outlet shall be corrosion resistant material.
3.11.6.1 Mounting rails. Mounting rails shall be located on the sides of the unit, flush with the top surface of
the cabinet, as shown in Figure 3. Mounting rails shall be of sufficient strength to support individual units under HI
shock in accordance with MIL-S-901 for grade A, class I, type A equipment. Mounting rails shall be predrilled as
specified on Figure 4 to standardize mounting for interchanging units.
3.11.6.2 Insulation.
3.11.6.2.1 Thermal insulation. All internal surfaces of the cabinet or chassis that are subject to condensation
shall be provided with insulation to prevent dripping or a continuous flow of moisture under rated capacity
conditions. Insulation shall be of a non-halogenated closed cell type and shall not produce toxic smoke when
exposed to a fire.
3.11.6.2.2 Acoustic insulation. Where acoustic insulation is required, it shall be such that it will satisfy both
thermal and airborne noise requirements. Acoustic insulation shall not produce toxic smoke when exposed to a fire.
3.11.6.3 Access panels. Provision shall be made to permit access to and removal of fan, fan motor, electric
heater, electrical controls, and cooling coil. Bolted, removable access panels, if used, shall be formed and flanged
and shall be interchangeable on fan-coil units of the same type and size. Flanged surfaces, which support removable
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