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 TM 55-1905-219-14-8
4-28.
AIR CONDITIONING SYSTEM-MAINTENANCE INSTRUCTIONS (Continued).
Heat Interchanger Data
Manufacturer
Dunham Bush (Heat X Inc.)
Model No.
7-1/2 SX
Overall Length
22-3/4" (56.7 cm)
Shell Diameter
3-1/2" OD
Connections
7/8" OD liquid,
1-5/8" suction
(9)
Dryer.
(a) The dryer or dehydrator, installed in the main liquid line or in a bypass, is a cylinder containing
renewable cartridges filled with activated alumina or silica gel. The dryer is used to keep the system free of
moisture.
(b) When the dryer is installed in the main liquid line, it remains in operation at all times. When it
is installed in a bypass, the dryer is to be used when charging refrigerant or for freeing the system of moisture.
If the system is properly purged and dehydrated when first installed, and operated with care, it will be necessary
to use the dryer only when charging.
(c)
Some dryers are equipped with a "dry eye" or moisture indicator consisting of a paper disc
visible through a sight glass. The paper disc changes in color from blue to pink. A blue tinge indicates an
acceptable level of moisture in the refrigerant. A pink color indicates excessive moisture and the need for
replacement of dryer cartridges.
(10) Cooling Coil.
(a) The cooling coil is of the direct expansion type (refrigerant-12 flows through the coil). The coil
is constructed of copper finned tubes, headers and connections. The parts are encased in a steel casing and
hot dipped galvanized.
(b) The cooling coil lowers the supply air in temperature and dehumidifies to meet design
conditions. Refrigerant flow through the coil is regulated by a thermostatic expansion valve in response to
changes in superheat of refrigerant gas leaving the coil. Refrigerant flow to the expansion valve is controlled
by a solenoid valve, which is regulated by the temperature control switch in response to changes in return air
temperature. General data on the cooling coil is tabulated below.
4-815
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