Operating instructions

Domestic Hot Water Mode
To be able to supply hot water, the selector switch (34 fig.
6) must be in either on ,,? or ‘1111 ,i position. This will be
confirmed by the green indicator light 0 (38 fig. 6).
The hot water temperature in the mini cylinder can be
adjusted between 40°C and 60°C using control knob (36
fig 6).
When a tap or shower is turned on and the flow of mains
water is above 2 litres per min., it will activate the DHW
flow switch 30 fig 7 and allow the 3 way valve (15 fig. 7)
to move to the DHW position. The pump can now
circulate primary water heated by the main heat
exchanger through the secondary heat exchanger.
The safety solenoid (3a fig. 7) and the first stage solenoid
(3b fig. 7) open together to allow gas to the burner. The
ignition sequence begins and a continuous high speed
spark ignites the gas. As soon as a flame is detected the
orange indicator bulb 0 (39 fig. 6) will light and the
second stage solenoid (3c fig. 7) opens to allow the full
gas rate. If a flame is not detected, after 8 seconds, the
safety solenoid and the first stage solenoids close and
shut off the gas. The red lockout indicator bulb 0 (40 fig.
6) will light.
Over 2 Vmin, the domestic hot water temperature is
controlled by the hot water control thermistor (32 fig. 7)
and the heating control thermistor (14 fig. 7), but
dependant upon to the position of the DHW temperature adjustment
knob (36 fig. 6). This system anticipates the changes of
temperature in the secondary heat exchanger and ensures accurate
temperature regulation.
When the tap is closed the burner is extinguished and the pump
runs on for 10 seconds (unless the mini cylinder thermistor is calling
for heat, in which case the burner will remain on at a low rate and
the pump will continue running until the mini cylinder thermistor is
satisfied). The boiler will now stay in the hot water mode for 30
seconds to be ready for a subsequent draw off (this can be set to 3
minutes if required. See Maintenance and Service Guide).
Priority is given to a demand for hot water. This will interrupt the
central heating for the duration of hot water delivery or recovery of
the mini cylinder.
When the boiler has been in standby in Hot Water Mode for some
time or when drawing DHW at flow rates of less than 2 Vmin the
temperature in the mini cylinder will eventually decrease and the