NGW 300 / LGW 300 / GBW 300
2 General description
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2.10 Regulating thermostat
The regulating thermostat (bimetal) measures the coolant
temperature at the water outlet of the heat exchanger. The
signal is conducted to the control unit and is processed
there.
The system is switched off at 75±3°C
and is switched on again at 68±5°C.
2.11 Temperature limiter
The temperature limiter (bimetal) protects the heater
against incorrect high temperatures. The temperature li-
miter acts at a temperature above 125°C and switches off
the heater.
The temperature limiter may be reset mechanically, once
a temperature of 90 °C has been reached.
2.12 Circulating pump
The circulating pump which is located externally guaran-
tees that the coolant is conveyed in the vehicle’s or the
heater’s circuit.
The circulating pump is switched on by the control unit
and runs throughout the entire operation of the heater.
The heater can be operated with the U4814, the U4851 or
the Aquavent 6000 S (U 4852) circulating pump.
2.12.1 The U 4851 and Aquavent 6000 S
(U 4852) circulating pumps
The U 4851 / Aquavent 6000 S (U 4852) circulating pump
is equipped with a brushless motor.
Soft start
The motor starts slowly and protects its material from wear.
It reaches its maximum speed only after approx. 5 seconds.
Protection against dry running
A dry running protection system is integrated into the mo-
tor for speeds of 3,300 rpm.
If the motor consumes less than 4 A of current in a timef-
rame of 1018 revolutions, it detects that it is running dry.
The motor is switched off when it goes into error mode (af-
ter approx. 10 seconds of operation or approx. 15 secon-
ds after being switched on.
For the Aquavent 6000 S circulating pump (U 4852) the
permitted dry running was extended to 45 minutes.
Blocking protection
If the operating speed falls below 57 rpm, the motor is
switched off by the error mode after approx. 1 second.
If the motor fails to complete a revolution in 1 second, de-
spite having a current feed , it is switched off by the error
mode.
Temperature limiter
Regulating thermostat
U 4851
Aquavent 6000 S
(U 4852)
U 4814