3.0 Appliance Operation
6
3.1
1.
Switched Live On:
When the switched live
switches on pump overrun occurs.
2.
Pump Overrun:
The pump is on while the fan,
spark generator and gas valve are off. If at any
stage during pump overrun the flow temperature
is less than the set point and the flow switch is
made then fan purge occurs. After 1 minute of
pump overrun anti-cycle occurs.
3.
Fan Purge:
The pump and fan are on while
the spark generator and gas valve are off. After 5
seconds ignition occurs.
4.
Ignition:
The pump, fan, spark generator and
gas valve are on. If a flame is detected then
burner on occurs. If a flame is not detected within
5 seconds and less than 5 ignition attempts have
been made then fan purge occurs. If a flame is
not detected within 5 seconds and 5 ignition
attempts have been made the ignition lockout
occurs.
5.
Burner On:
The pump, fan and gas valve are
on while the spark generator is off. Flow
temperature is controlled by varying the fan
speed (and thereby the gas rate) to achieve
optimum operation. If the flow temperature is
greater than the set point then pump overrun
occurs. If the TRVs all shut down then anti-cycle
occurs.
6.
Anti-cycle:
The pump, fan, spark generator
and gas valve are switched off. After 3 minutes
pump overrun occurs.
7.
Ignition Lockout:
The pump, fan, spark
generator and gas valve are switched off. The
boiler can only be reset by manually using the
thermostat knob.
Mains On.
Flow
temperature less
than set point and flow
switch made ?
YES
5 second
Fan Purge.
Flame Detected ?
Burner On.
Ignition
Lockout.
5 second
Ignition Period.
All TRVs
shut down ?
Flow temperature
greater than set
point ?
Ignition done and
5 attempts made ?
Ignition done
and less than 5
attempts made ?
Pump Overrun
Anti-cycle.
Pump Overrun
for 1 minute ?
YES
YES
YES
YES
YES
YES