7
1.2.3 Operation of the storage
water heater.
Normal operation
When there is a demand for heat a
waiting period of about 1 second
elapses before the built-in spark gene-
rator and pilot gas valve are switched
on. The ignition sparks ignite the pilot
burner and the resulting flame is
detected by the ionisation electrode.
Almost immediately after the pilot flame
is detected, sparking stops and the
main gas valve is openend. The main
burner is lit by the pilot flame. The unit
is now in operation. When the
temperature of the water in the unit
reaches the temperature that is set
with the thermostat, the thermostat
switches and disconnects the
electrical heat demand signal to the
burner controller. The gas valves are
then closed.
Ignition failure
If the flame is not established within
the safety period the automatic ignition
controller locks out. The safety period
is about 25 seconds. Lock-out is
indicated by the lamp in the RESET-
button on the control panel. The unit
has to be manually reset by pushing
the reset button. If the flame is lost
during normal run, the automatic
ignition controller repeats the start
sequence.
1.2.4 Combustion products
discharge safety device
The water heater has been fitted with
a combustion products discharge
safety device.
It is the function of the safety device to
prevent flue gases from the water
heater entering the room where the
water heater has been placed, instead
of passing through the flue to outside
atmosphere. The gas supply is
disconnected as soon as the device is
activated by hot gasses flowing over
the sensor.
After the cause of the re-entry of flue
gasses has been traced the device
can be put back into operation by
pressing its reset button.
If this failure occurs frequently, this
indicates that the flue suffers from down
draught conditions. It is recommended
that a competent person carry out the
necessary remendial action.
Important
The combustion products dis-
charge safety device should never
be put out of operation.
Re-entry of flue gasses to the buil-
ding could be harmful and cause
poisoning or death.
