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 TM 55-1905-220-14-9
4-42. WASHER/DRYER - MAINTENANCE INSTRUCTIONS (Continued).
(2)
Heat control thermostat.
(a)
The heat control thermostat located on the blower housing is a bi-metal disc snap action type.
The temperature of the air passing across the switch causes the bi-metal disc to distort, from concave to
convex or convex to concave, according to temperature rise or fall, opening or closing the internal contacts.
The switch is of a single pole double throw type, opening the contacts between terminals 1 and 3 and closing
contacts between 1 and 2 on temperature rise. On temperature fall contacts between terminals 1 and 2 open
and contacts between 1 and 3 close.
(b)
The thermostat incorporates an internal biasing heater that is used to change the air temperature
required to warp the bi-metal disc that operates the internal contacts. The heat produced internally by the disc
heater reduces the temperature intensity requirement of the circulating air by approximately 15 degrees.
(c)
The internal disc heater enables the same thermostat to be used to control the product air
temperatures at two different temperatures depending on whether the biasing or disc heater is energized or not
by the heat selector switch contact 2.
NOTE
One end of the 240 (208) volt biasing heater is connected
internally to terminal 3 and is therefore energized only when the
thermostat contact is closed to energize the heating element on
Delicate cycles. This results in a reduced thermostat differential
as well as reduced operating temperature on the Delicate
setting.
(3)
Fabric selector switch. A rotary type switch that is set by the user to select the proper temperature
for the clothes load being dried. Contacts within the switch determine the flow of current to different segments
of the dryer heater. The selection of delicate results in lower air temperature during the drying cycle provided
the preset time setting is not too long for the load being dried.
(4)
Safety thermal fuse. A heat operated thermal fuse is located in the blower housing as additional
protection against over-heating of the circulating air. If the air temperature rises to the melting point of the fuse
link, the dryer motor circuit is thus broken, resulting in shut down of the motor and disconnecting the heater
circuit through the motor speed switch contacts. This thermal fuse is located next to the heat control
thermostat.
Change 1
4-1065
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