The coolant heater will continue to cycle on and off as described in steps b, c, and d until
it is either manually (by depressing the Heater "On"
pushbutton) or automatically
(seven day timer times out) shuts down.
If the coolant heater flames out while in the running mode, the control unit
(4) will automatically re-start the heater. If the coolant heater does not re-
start after one attempt, the control unit (4) will shutdown the heater.
The coolant heater control unit (4) continually senses the input voltage
from the crane's batteries. If the input voltage drops below 20 VDC or
rises above 30 VDC, the heater control unit (4) will automatically
shutdown the coolant heater.
The coolant heater can be shutdown manually (by depressing the Heater "On"
automatically (via the seven day timer). The following sequence occurs:
When switched off, the coolant control unit (4) initiates a heater cool down cycle.
The fuel metering pump (13) stops running and the flame is extinguished.
The combustion air blower motor (1) and water pump (10) continue operating for
approximately three minutes to cool down the coolant heater combustion chamber.
The coolant heater shuts down after the cool down period. The combustion air blower
motor (1) and the water pump (10) stop running.
The coolant heater control unit (4) monitors the heater for malfunctions. The unit employs temperature
(6), overheat (9), and flame (2) sensors to monitor coolant heater performance. The coolant heater will
shut down whenever a malfunction occurs.
The control unit (4) performs a self-test of the electrical circuit prior to starting the coolant
The control unit (4) will automatically repeat the startup sequence if the flame sensor (2)
fails to detect a flame 90 seconds after the fuel metering pump (13) comes on. If the
heater fails to ignite after the second 90-second timer times out, the control unit (4) will
perform a safety shutdown.
The control unit (3) will attempt to re-ignite the coolant heater if it fails or flames-out
during operation. If the heater fails to re-ignite after ten seconds or if the heater flames
out again after only three minutes of operation, the control unit (4) will initiate a flame out
shutdown. The coolant heater cannot be restarted until the problem is corrected.
Overheating can occur when the coolant flowing through the coolant heater is low,
restricted, or poorly bled. The overheat sensor (9) will most likely detect a temperature
rise in the coolant heater's heat exchanger. When this occurs, the control unit (4) will
perform an overheat shutdown of the heater. Again, the problem should be corrected
before attempting to re-start the heater.