Technical data
3.0 Appliance Operation – page 6
NOTE: All delay timers mentioned in 3.1 and 3.2 are
overridden by domestic hot water demand.
3.1 Central Heating Mode
1. With a demand for heating, the pump circulates water
through the primary circuit. At a flow rate of
approximately 125 I/hr the central heating flow switch
operates, initiating the ignition sequence.
2. The main burner ignites at low rate, then the gas valve
controls the gas rate to maintain the heating
temperature measured by the thermostat sensor.
3. When the flow temperature exceeds the setting
temperature, a 3 minute delay occurs before the burner
relights automatically (anti-cycling). The pump
continues to run during this period.
4. When the demand is satisfied the burner is
extinguished and the pump continues to run for a
period of 30 seconds (Pump Overrun).
3.2 Domestic Hot Water Mode
1. Priority is given to the domestic hot water supply. A
demand at a tap or shower will override any central
heating requirement.
2. The flow of water will operate the DHW flow switch
which requests the 3 way valve to change position. This
will allow the pump to circulate the primary water
through the DHW plate heat exchanger.
3. The burner will light automatically and the temperature
of the domestic hot water is controlled by the
thermostat sensor.
4. When the domestic hot water demand ceases the
burner will extinguish and the diverter valve will remain
in the domestic hot water mode, unless there is a
demand for central heating.
3.3 Frost Protection Mode
1. The frost protection mode is integral to the appliance
when left in the domestic hot water and central heating
position. If the system temperature falls below 5º C then
the boiler will fire on its minimum setting until a flow
temperature of 30º C is reached. Further protection can
be incorporated by using a system frost thermostat.
3.4 Pump Protection
1. The control system continually monitors the time since
the pump last operates. This will result in the pump
being run for 10 seconds every so often to prevent
seizure.