Supplied By www.heating spares.co Tel. 0161 620 6677
23
NOTE
If the spark/sensing electrode does not sense
ignition the appliance will then go to lockout.
Ignition is sensed by the electronic circuitry to
ensure flame stability at the burner. Once suc-
cessful ignition has been achieved, the electronic
circuitry modulates the appliance output in order to
achieve the DHW set-point (the position of the
DHW temperature selector) as measured at the
secondary thermistor.
When the set-point has been reached, the appli-
ance will begin the modulation phase whereby the
fan and gas valve will continuously modulate to
maintain the set-point.
If the temperature continues to rise and exceeds
the set-point by 5 °C, the burner will shut down until
the temperature drops to set-point + 4 °C, whereby
a new ignition sequence will be enabled.
When the request for DHW has been satisfied, the
appliance fan may continue to operate to dissipate
any residual heat from within the appliance.
7.2.5.1 DHW PARAMETERS
7.2.6
HEATING MODE fig. 33
With the selector switch in the Heating & HW
position and the relevant controls (time clock,
room thermostat, etc,) are calling for heat, the
appliance will operate in the heating mode. The
valve actuator will motor to the heating position
and the pump and fan will be active. The operation
of the fan causes the air pressure switch (APS) to
deliver a signal voltage to the control PCB. A slow
ignition sequence is enabled, whereby the current
supplied to the gas valve modulating coil is pro-
gressively increased from minimum to maximum
over a period of 8-seconds. During this period the
ignition electrode sparks continuously even if the
burner has ignited.
NOTE
If the spark/sensing electrode does not sense
ignition the appliance will then go to lockout.
Ignition is sensed by the electronic circuitry to
ensure flame stability at the burner. Once suc-
cessful ignition has been achieved, the electronic
circuitry allows 75% of the full gas rate through the
appliance. After 15 minutes the gas rate is increased
to maximum (100%).
When the set-point has been reached (the position
of the heating temperature selector) as measured
at the primary thermistor, the appliance will begin
the modulation phase whereby the fan and gas
valve will continuously modulate to maintain the
set-point.
If the temperature continues to rise and exceeds
the set-point by 6 °C, the burner will shut down and
the boiler will perform a three-minute anti-cycle
(timer delay).
A new ignition sequence will be enabled when the
3-minute anti-cycle has been performed and the
temperature at the primary thermistor has dropped
6 °C below the set-point.
NOTES
The timer delay can be de-activated by the inser-
tion of a ‘jumper’ on the PCB at JP1 or by isolating
the appliance from the electrical supply for 30
seconds.
Any DHW requests will always have priority over
a heating request.
When the request for heating has been satisfied,
the appliance pump and fan may continue to
circulate to dissipate any residual heat within the
appliance.
Fig. 32
RANGE
MINIMUM
MAXIMUM
Temperature (°C)
37.5
60
DHW NTC fault
ON at 50 °C
OFF at 55 °C
Fig. 33
