TM 9-4520-258-14
1-12. ELECTRICAL SYSTEM - continued.
(2)
Temperature Controller Circuits. The components comprising the temperature control circuits are the
discharge air thermostat (S3), the temperature limit switch (S2) and the remote temperature thermostat (S6).
(a)
When the MODE SWITCH (S1) is in the AUTO HEAT mode, the remote temperature thermostat
(S6) controls the unit temperature output (from 35°F to 85°F). The burner will cycle to the
temperature setting on the remote thermostat (S6) unless the output exceeds 150°F. When the
temperature exceeds 150°F the discharge air thermostat (S3) cycles the burner to OFF until the
outlet temperature is below 150°F.
(b)
While still operating in the AUTO HEAT mode, the remote thermostat (S6) can be placed in HI
by depressing both of the control buttons (arrows) at the same time. The display screen on the
remote thermostat (S6) will indicate HI. The burner will now burn continuously unless the outlet
temperature exceeds 150°F. When this happens, the discharge air thermostat (S3) will again
turn the burner OFF until the outlet temperature is below 150°F.
(c)
When in the MANUAL HEAT mode, the remote thermostat (S6) and the discharge air thermostat
are bypassed and the burner is on continuously unless the outlet temperature exceeds 200°F.
When outlet temperatures exceed 200°F, the temperature limit switch (S2) shuts down the
burner but the circulating air fan and the combustion air fan continue to operate. The HIGH
TEMP light (DS2) will illuminate. The flame sensor (DL) will sense no flame and the FLAME
OUT light (DS3) will illuminate.
1-13. FUEL SYSTEM.
a.
General. The fuel system is illustrated schematically on Figure 1-5. The fuel system incorporates a 14-
gallon internal fuel tank. A fuel transfer valve V1 enables operation of the heater from the internal fuel tank or from an
external fuel source using a 25-foot fuel hose.
b.
Purge System. The purge system enables the operator to purge air from the fuel system upon initial startup
of the heater. Purging is also required when operating from an external source and after the fuel system has been
allowed to run dry.
CAUTION
Do not operate unit without fuel. Operation without fuel will result in damage to fuel pump.
Never attempt to operate the ASH Unit with the fuel selector valve handle in a vertical position.
Fuel will not flow with the handle in the vertical position. The fuel selector valve handle must be
in a horizontal position.
Internal tank may be over serviced during purging if the external fuel source is used. Never
purge the system on external tank when internal tank is full.
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