A.O. Smith SGE Installation And Operation Manual page 62

9
The complete cycle is explained in the following example,
which assumes the appliance is in the basic mode ON.
Note
The same heating cycle applies to the other
operating modes.
Once the appliance starts, it will run through the
following steps:
1. The water temperature drops below the set
temperature of (for example) 65°C. The electronic
controller detects a demand and starts the heating
cycle.
- The icon is activated.
- The message HEAT DEMAND appears.
a
ON Ê
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Tset 65ÉC
HEAT DEMAND
2. Once demand is registered, the fan is started to
exhaust any gases that may be present. This phase
is called pre-purge and lasts about 15 seconds.
- The icon is activated.
- The message PRE PURGE appears.
a
ON Ê Ê
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PRE PURGE
3. During the pre-purge, the pressure switch closes.
- The icon is activated.
- The message PRESSURE SWITCH
appears.
a
ON Ê Ê Ê
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PRESSURE SWITCH
4. After some time, the pre-purge ceases and the
electronic controller reduces the fan speed to the
ignition speed. This is followed by the (pre-)glow of
the hot surface igniter.
- The icons and
- The icon is activated.
a
ON Ê Ê
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GLOW PLUG
62
Starting and running
are dimmed
5. After a number of seconds pre-glow, the gas
control is opened and ignition takes place.
- The icon is activated.
- The message IGNITION appears.
a
ON Ê Ê Ê
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IGNITION
6. After ignition, the flame is detected and the
appliance will be running. This means that actual
heating has started. The fan speed then increases
to the normal working speed, and the pressure
switch closes:
- The icon is dimmed.
- The icons and
- The message RUNNING appears.
a
ON Ê Ê Ê Ê
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RUNNING
7. When the water is up to temperature, the heat
demand drops off and the post-purge starts. This
lasts about 25 seconds.
- The icons , and
- The icon is activated.
- The message POST PURGE appears.
a
ON Ê Ê
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POST PURGE
8. Following the post-purge, the fan stops and the
pressure switch opens:
- The icons and
- The message POST PURGE vanishes.
a
ON
14:05 Thursday 65ÉC
With any subsequent heat demand, the heating cycle
will resume from step 1.
gis
are activated.
are dimmed.
are dimmed.
Instruction manual SGE