Ignition Electrode - Bosch GWI-N Series Training And Service Information

In order to improve the temperature stabilization at the outlet and avoid temperature overshoot, a bypass with
controlled valve is included in high output range (16 / 20 / 26 l/min)
In case the difference between the detected outlet temperature and the set temperature is higher than 3ºC, the
controlled water valve will open the cold water passage to the outlet, according to the corresponding inlet water
flow (quantity could vary according overshoot peak – voltage variation up to 24 V dc).
Pict.37 – By-pass valve

4.12 Ignition electrode

Spark generation is started immediately before opening the gas valve, and stopped when ionization is
sensed.
Pict.38 – Ignition electrode
In order to prevent harder ignition processes and be sure of conditions of gas supply and burner stability,
following situation is verified during the so called safety time period.
In each of the attempts, the system monitors the ionisation signal; this signal drives the start of normal
operation, however and, in case the ionization signal is not detected during the ignition sequence, the failure
indication EA will be displayed. In this case a non-volatile lock-out is activated, and only a manual reset can
lead the system back to normal operation. If the ionisation signal is interrupted during normal operation, this
ignition sequence is re-started.
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