Functional Description; General Description; High Pressure Pump, Water System; Electric Motor - Alto 3840HA Instruction Manual

5.0 Functional description

5.1 General description

The water passes from the quick coupling (1) through a water filter (2) and enters the float chamber, from
which it leads into the high pressure pump. The high pressured water leads through the discharge
system of the pump where the safety valve and the circulation valve are situated. Then it passes the
flow switches (13) and enters the boiler (15). Here the water is heated to the required temperature.
After the boiler the hot high pressure water passes the temperature sensor (17), on to the spray handle
(19) and the spray lance. The fuel is drawn from the fuel tank (32) through the fuel filter (23) by the fuel
pump (25). Now the pump leads fuel to the nozzle (16) where it is ignited.

5.2 High pressure pump, water system

On the pressure side the high pressure pump features a circulation valve. This valve leads the water
back to the suction side of the pump, when the spray handle is closed or if a nozzle is blocked. Beyond
that a safety valve has been mounted to ensure that the pressure will never exceed the preadjusted
pressure, which is approx. 25 bar above the working pressure. The valve has been adjusted and sea-
led from the factory. This adjustment must not be changed! When the machine stops it is automatically
devoid of pressure.

5.3 Electric motor

The motor is protected against overloading through two systems. A thermal cut-out has been built into
the stator windings. If the motor is overloaded or if the cooling system for the motor is interrupted the
thermal cut-out will cut off the power to stop the machine. Then it cannot be restarted on the control
panel until the motor has cooled. Besides the operation of the motor is surveyed by an electronic motor
protection device, which prevents the rated power consumption of the motor from being exceeded. In
the case of an excess the power supply for the motor will be cut off and the machine will stop. In this
case a fault code will be shown on the display (see section 7.0 Trouble shooting chart). If the power
fails, the machine must be restarted.

5.4 Burner system - control system

The burner system is surveyed and controlled by an electronic control unit with a built-in micro processor.
The operational conditions of the incorporated components of the burner system is surveyed by sensors. In
conjunction with the control unit the sensors ensure a correct function of the machine and they ensure that
the machine is stopped in the event of malfunctions, upon which a fault code is shown on the display.
The following sensors are built into the system:
- Flow control, double (13)
Ensures the water flow through the boiler, before it can be ignited.
Allows solenoid valve (29) to open.
- Flame sensor (light sensor) (30)
Surveys that the boiler is actually burning when fed with fuel, and that the boiler will go out when the fuel
supply is cut off.
- Temperature sensor (17)
Measures the temperature of the high pressure water from the boiler. Dependent on higher or lower
temperature the burner will ignite or turn out.
- Level switch for tank (24)
Ensures that the tank cannot be completely emptied. Machine stops before that happens.
- Phase sequence pressure switch (31)
Check, by measuring the air pressure of the blower, that the motor of the machine is running in the
correct direction of rotation and that the air supply for the boiler and the motor cooling are correct.
The machine will stop, if a too low air pressure of the blower is registered.

5.5 Burner override mode

As an additional safety device a safety thermostat has been added at the inlet of the burner coil which will
detect an unacceptable rise in water temperature before the coil (such as might be caused by constant fuel
supply to the burner). The safety thermostat will stop the machine after approximately 40 sec. (when the
temperature at the water inlet has reached approximately 60
ever-temperature condition, no failure codes will be displayed. Arrange for service assistance immediately.
16
3840HA_EU.p65 16
O
C). If the machine stops as a result of this
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