GF83.70-D-2001HZZ Heater Operation, Function

GF83.70-D-2001HZZ Heater Operation, Function
MODEL 906.111 /113 /131 /133 /135 /153 /155 /211 /213 /231 /233 /235 /253 /255 /611 /613 /631 /633 /635 /637 /653 /655 /657 /711 /713 /731 /733 /735
- with CODE (HZ9) Heater booster, diesel
- Heater booster (ZUH)

MODEL 906.611 /613 /631 /633 /635 /637 /653 /655 /657 /711 /713 /731 /733 /735
- with CODE (HZ5) 10 kW warm water auxiliary heater with timer
- Heater booster (ZUH)

As soon as the warm water auxiliary heater 2 control unit (N33/2) receives the switch-on signal from one of the following components, the heater operation of the heater booster heater unit is started immediately:
- Stationary heater switch (S46/10), with code (HZ9) Heater booster, diesel
- Warm water stationary heater switch (S46/11), with code (HZ5) 10 kW warm water auxiliary heater with timer

The stationary heater switch has a "Memory function" (automatic heater operation activation of the heater booster heater unit). The "Memory function" remains active (also in the event of a status change of circuit 15 and circuit 61) until it is deactivated again by operating the stationary heater switch in the upper subfield.

The warm water stationary heater switch has a "Memory function" (automatic heater operation activation of the heater booster heater unit). The "Memory function" remains active (also in the event of a status change of circuit 15 and circuit 61) until it is deactivated again by operating the warm water stationary heater switch in the upper subfield.

On vehicles with code (HZ9) Heater booster, diesel, activation of the heater operation of the heater booster heater unit is indicated by the red light emitting diode (LED) in the stationary heater switch going on.

On vehicles with code (HZ5) 10 kW warm water auxiliary heater with timer, activation of the heater operation of the heater booster heater unit is indicated by the red light emitting diode (LED) in the warm water stationary heater switch going on.
The runtime of the heater booster heater unit operation is unlimited until a status change to "circuit 61 OFF" takes place.
The heater operation of the heater booster heater unit is subdivided into the following 4 sections:
- Startup phase
- Heating mode
- Control mode
- Caster

Startup phase
In the startup phase, the warm water auxiliary heater 2 control unit actuates the glow pin (N33/2r1), the blower motor (N33/2m1) of the ZUH combustion air blower and the circulation pump (M13/4).
The glow pin is responsible for preheating, the ZUH combustion air blower ensures ventilation of the combustor with downpipe, and the circulation pump ensures circulation of the coolant.
After t = 5 s, actuation of the blower motor of the ZUH combustion air blower is interrupted. After t = 35 s, the blower motor of the ZUH combustion air blower is actuated again and after t = 42 s, the metering pump (M46/4) is actuated by the warm water auxiliary heater 2 control unit. The blower motor of the ZUH combustion air blower is responsible for the supply of combustion air and the metering pump ensures the supply of fuel. The supplied combustion air and the supplied fuel form an ignitable mixture, which is ignited at the glow pin.
If the warm water auxiliary heater 2 control unit detects correct combustion in the combustor with downpipe via the flame sensor (N33/2b2) after t = 120 s, the stationary heater unit switches to "Heater operation".
In addition, the warm water auxiliary heater 2 control unit places the message "ZHZ_EIN (heater booster function switched on)" on the Controller Area Network bus class B (interior) (CAN-B).
If the warm water auxiliary heater 2 control unit does not detect correct combustion in the combustor with downpipe via the flame sensor after fuel has been supplied for t = 90 s, the start procedure of the heater booster heater unit is repeated in the described manner.
If the warm water auxiliary heater 2 control unit does not detect correct combustion in the combustor with downpipe via the flame sensor after fuel has been supplied for another t = 90 s, a fault shutoff of the heater booster heater unit takes place and the heater booster heater unit switches to power-down mode.

After an impermissible number of fault shutoffs of the stationary heater unit, the warm water auxiliary heater 2 control unit is locked

If the glow pin is defective or the electrical line of the metering pump is interrupted, the heater booster heater unit will not start.

Heating mode
During heater operation, the warm water auxiliary heater 2 control unit interrupts actuation of the glow pin and continuously regulates the blower motor of the ZUH combustion air blower as well as the metering pump to a higher output.
The ignitable mixture will now automatically ignite at the hot walls of the combustor with downpipe. The warm water auxiliary heater 2 control unit continues activating the circulation pump.
The heater booster heater unit is now set to power output stage "High (5 kW)".
During heater operation, depending on the actuation by the warm water auxiliary heater 2 control unit, heater operation is regulated to "Control mode" in the power output stages "High (5 kW)" or "Low (2.4 kW)".

Control mode
In control mode, the warm water auxiliary heater 2 control unit actuates, depending on the required power output stage "High (5 kW)" or "Low (2.4 kW)", the following components:
- Blower motor of ZUH combustion air blower
- Metering pump

For vehicles except code (HH9) Regulated air conditioning (Tempmatic), the control mode depends on the coolant temperature, and for vehicles with code (HH9) Regulated air conditioning (Tempmatic), it additionally depends on the temperature value set via the temperature selection switch (S98s14) integrated in the automatic air conditioning control and operating unit (S98).
The switch-on requirement for the heater booster heater unit is a coolant temperature of < 75 °C. At a coolant temperature of > 80 °C, the setting of the heater booster heater unit is reduced to power output stage "Low (2.4 kW)".

If the coolant temperature increases to > 85 °C although the power output stage is set to "Low (2.4 kW)", the heater booster heater unit switches to a control break. In the control break, actuation of the blower motor of the ZUH combustion air blower and of the metering pump is interrupted by the warm water auxiliary heater 2 control unit, and the heater booster heater unit switches to power-down mode for t = 130 s.
The circulation pump continues being actuated by the warm water auxiliary heater 2 control unit.If the coolant temperature drops to < 75 °C, the blower motor of the ZUH combustion air b lower and the metering pump are actuated again and the heater booster heater unit switches to control mode again.
To this end, the warm water auxiliary heater 2 control unit receives the messages of the following components via CAN-B:
- Coolant temperature sensor (B11/4)
- Interior compartment temperature sensor (S98b1), via the KLA control and operating unit, with code (HH9) Regulated air conditioning (Tempmatic)

If the warm water auxiliary heater 2 control unit recognizes a flame- out via the flame sensor during heater operation or control mode, the start procedure of the heater booster heater unit is repeated in the described manner.
If, after a restart, the warm water auxiliary heater 2 control unit does not detect correct combustion in the combustor with downpipe via the flame sensor after fuel has been supplied for another t = 90 s or if the flame goes out after t = 15 min after the heater has been operated again, a fault shutoff of the heater booster heater unit takes place and the heater booster heater unit switches to power- down mode.

The heater booster heater unit fault shutoff can be canceled a maximum of 2 times by switching the heater booster heater unit on and off.

If the warm water auxiliary heater 2 control unit recognizes overheating of the stationary heater unit (> 90 °C) via the overheating sensor (N33/2b3) during heater operation or control mode, actuation of the metering pump is interrupted. There is a fault shutoff of the heater booster heater unit, and the heater booster heater unit switches to power-down mode.
After the cause of the overheating has been eliminated and the heater booster heater unit has cooled off (< 70 °C), heater operation can be restarted by switching the heater booster heater unit on and off.
During the start phase, during heater operation and in control mode, the rotational speed of the blower motor of the ZUH combustion air blower is monitored by the warm water auxiliary heater 2 control unit.If the blower motor of the ZUH combustion air blower does not start up or if the rotational speed drops below 40 % of the nominal value, a fault shutoff of the heater booster heater unit occurs after t = 60 s and the heater booster heater unit switches to power-down mode.

Terminate heater operation of heater booster heater unit
The heater operation of the heater booster heater unit is terminated after a status change from "circuit 61 ON" to "circuit 61 OFF" or after the warm water auxiliary heater 2 control unit receives the switch-off signal via the following variants:
- Stationary heater switch, with code (HZ9) Heater booster, diesel
- Warm water stationary heater switch, with code (HZ5) 10 kW warm water auxiliary heater with timer

The stationary heater switch has a "Memory function" (automatic heater operation activation of the heater booster heater unit). The "Memory function" remains active (also in the event of a status change of circuit 15 and circuit 61) until it is deactivated again by operating the stationary heater switch in the upper subfield.

The warm water stationary heater switch has a "Memory function" (automatic heater operation activation of the heater booster heater unit). The "Memory function" remains active (also in the event of a status change of circuit 15 and circuit 61) until it is deactivated again by operating the warm water stationary heater switch in the upper subfield.

After heater operation has ended, the heater booster heater unit switches to power-down mode.

Delayed-off running
In power-down mode, the warm water auxiliary heater 2 control unit actuates the blower motor of the ZUH combustion air blower and the circulation pump for t = 120 s as well as the glow pin for t = 20 s. The blower motor of the ZUH combustion air blower is used to cool off the combustor with downpipe of the heater booster heater unit through the generated air suction and to discharge combustion gases.
The circulation pump is used to cool off the heat exchanger of the heater booster heater unit through the coolant flowing by. The glow pin burns itself off during this time.
The warm water auxiliary heater 2 control unit places the message "STH_ZHZ_EIN (heater booster switched on)" on the CAN-B until the power-down mode has ended.