Electrical Diagram; Function - Bosch Therm 4300 Series Installation And User Instructions Manual

Gas instantaneous water heater
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Technical Characteristics and Dimensions
2.7

Electrical diagram

Fig. 2
Electrical diagram
[2] Spark plug
[3] Ionisation probe
[23] Ignition unit
[25] Servo valve (normally open)
[28] Gas valve (normally closed)
[31] Temperature limiter
[32] Flue gas safety device
[33] Diaphragm valve
[34] LED - Burner status check
[35] Switch / LED - Low water flow indicator
[41] Temperature sensor
[42] Digital display
[50] Hydrogenerator
2.8

Function

This gas heater is equipped with automatic electronic ignition
which simplifies its operation.
▶ To do so, just turn on the switch (Fig. 4).
After this procedure, automatic ignition occurs whenever a hot
water tap is opened. First, the pilot burner is lit and
approximately four seconds afterwards the main burner. The
pilot burner flame is then extinguished after a short period of
time.
This is a way of saving a great amount of energy as the pilot
8
burner only operates for the minimum necessary time to ignite
the main burner, in contrast to conventional systems which
operate permanently.
Air in the gas supply pipe when the heater is
started up may cause ignition to fail.
If this happens:
▶ Close and open the hot water tap to repeat the ignition
process until all the air has been purged.
Therm 4300 – 6 720 821 607 (2018/01)

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Therm t4300 11-2dTherm t4300 14-2dTherm t4300 18-2d

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