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 TM 55-1905-219-14-8
4-33. GAGE BOARD - AIR CONDITIONING - MAINTENANCE INSTRUCTIONS.
a. High and Low Pressure Control Switches.
(1)
Operation.
(a)
Separate high and low pressure control switches. Similar in construction and
operation, are furnished.
(b)
Pressure applied at the switch connection actuates a seamless metallic bellows power
element which operates the switch mechanism to open or close the electrical circuit. A permanent magnet in
the switch mechanism provides a positive snap-action on both the opening and closing cycles, preventing
excessive arcing at the contacts.
(2)
Adjustment.
(a) The switch operating range and differential are both adjustable.
(b)
The range adjustment screw located on the right side of the switch, outside the case,
changes both the cut-in and cut-out points by an equal amount. Turning the range screw clockwise raises both
set points and turning it counterclockwise lowers both set points.
(c) The differential adjustment, inside the switch case, governs the cut-out point but does not
affect the cut-in point. Turning the differential screw clockwise widens the differential.
Pressure or Temperature Control Switch (American-Standard)
(3)
Schematic and Wiring Diagram. (See foldout 1.)
4-932
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