Other Features 5-31
PA-1628Operator's ManualH3-45 COACH
Once the flame sensor has signaled to the control
unit that combustion has taken place, the ignition
unit is switched off.
Hot combustion gases are diverted at the end of the
flame pipe and are then forced through the indirect
heating surfaces of the heat exchanger. The heat
exchanger transfers the heat to the coolant water
passing through the heat exchanger.
COOLANT PREHEATER
The heater is thermostatically controlled and
operates intermittently (i.e., the switched-on time of
the burner varies depending on the heat
requirement). The water temperature is controlled by
the built-in water thermostat.
The water circulation pump remains in operation as
long as the heater is operating, even during the
regulated intervals and during the delayed cut-out of
the heater. The pump can also be operated
independently of the heater by means of an
appropriate circuit. The heater can be switched on at
any time (i.e., during the delayed cut-out period).
Ignition takes place after the delayed cut-out time
expires.
SWITCHING THE HEATER OFF
The fuel supply is interrupted when the heater is
switched off. This causes the flame to go out and a
delayed cut-out of 3 minutes begins. The circulating
combustion air flushes the remaining combustion
gases out of the chamber and cools off the heated
parts on the exhaust side of the heat exchanger. The
water circulation pump continues to transfer the
latent heat present in the heat exchanger, thus
preventing hot spots. Once the delayed cut-out time
expires, both the combustion air blower and the
water circulation pump switch off automatically. A
cut-out will automatically take place in case of heater
failure. Refer to "PRE- HEATING SYSTEM" on
page18 in Section 9, Technical information for
specifications.
COOLANT HEATER TIMER
The timer, located on L.H. lateral console is used to
program the starting and stopping time of the
preheating system and to give Fault Codes. The
Heater "On" symbol , located on the timer, appears
when the system is in operation.
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