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1.1 PRINCIPLE COMPONENTS
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A fully integrated electronic control board featuring
electronic temperature control, anti-cycle control, pump
over-run, self-diagnostic fault indicator, full air/gas
modulation.
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Radial aluminium heat exchanger.
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Electronic ignition with flame supervision
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Fan
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Condensate level sensor.
1.2 MODE OF OPERATION (at rest)
When the appliance is at rest and there are no requests for
heating or hot water, the following functions are active:
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2-stage frost-protection system – the frost-protection
system protects the appliance against the risk of frost
damage. The first stage enables activation of the pump
should the temperature of the appliance fall to 6
o
C.
Should the first stage become active, the appliance will
function on m25% power until it reaches 35
o
C.
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Anti-block function – the anti-block function enables the
pump to be energised for short periods, when the
appliance has been inactive for more than 24-hours.
1.3 MODE OF OPERATION
When there is a request for heat and/or hot water, via the
programmer/time clock and/or any external control, the
pump and fan are started, the fan speed will modulate until
the correct signal voltage is received at the control PCB.
At this point an ignition sequence is enabled.
Ignition is sensed by the electronic circuitry to ensure
flame stability at the burner. Once successful ignition has
been achieved, the electronic circuit increases the gas
rate to 75% for a period of 15 minutes. Thereafter, the
boiler’s output will either be increase to maximum or
modulate to suit the set requirement.
When the appliance reaches the desired temperature the
burner will shut down and the boiler will perform a 5-minute
anti-cycle (timer delay).
When the request for heat has been satisfied the pump and
fan may continue to operate to dissipate any residual heat
within the appliance.
NOTE
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The pump must be connected directly to the designated
terminals within the appliance controls panel.
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When power is restored to the PCB and/or the PCB is
powered for the first time, the appliance will enter a 2-
minute purge cycle whereby only the pump will run for 15-
seconds then off for 15-seconds.
1.4 SAFETY DEVICES
When the appliance is in use, safe operation is ensured by:
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Fan speed sensor and pressure differential mechanism
to ensure safe operation of the burner.
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A high limit thermostat that over-rides the temperature
control circuit to prevent or interrupt the operation of the
burner.
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Flame sensor that will shut down the burner when no
flame signal is detected.
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A sensor that interrupts the operation of the appliance if
the condense pipe becomes blocked.
SECTION 1
DESIGN PRINCIPLES AND OPERATING SEQUENCE
Fig. 2
CH
return
CH
flow
return
temperature
sensor
main heat
exchanger
flow
temperature
sensor
top
AAV
water/air
separator
drain
valve