7
Domestic Hot Water Mode
In order to supply hot water, the main switch
23
(fig. 5) must
be in ON position
I
This will be confirmed by the green
indicator light
27
(fig. 5). Turn DHW temperature
adjustment knob
24
clock wise to establish the green DHW
indicator
32
(fig. 5).
The hot water temperature in the mini cylinder can be
adjusted between 40 and 60°C using control knob
24
(fig 5).
When a tap or shower is turned on, the flow of mains water,
above 2 litres per min., will activate the 3 way valve
17
(fig. 2) to move to the DHW position. The pump will now
circulate primary water heated by the main heat exchanger
through the secondary heat exchanger.
The first stage solenoid
a
(fig. 6) and safety solenoid
c
(fig. 6)
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
28
(fig. 5) will light and the second stage solenoid
b
(fig. 6) opens to allow the full gas rate. If a flame is not
detected, after 8 seconds, the security solenoid closes and
shuts off the gas. The red lockout indicator bulb
29
(fig. 5)
will show. Over 2 l/min, the domestic hot water temperature
is controlled by the hot water control thermistor
d
(fig. 6) and
the heating control thermistor
e
(fig. 6), but dependant upon
to the position of the DHW temperature adjustment knob
24
(fig. 5). 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 stops. (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
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 l/min the temperature in the mini cylinder will eventually
decrease and the TSS® control thermistor
f
(fig. 6) will call for
heat. Bringing the pump and burners to operate, until the
cylinder thermistoris satisfied. this is quite normal.
5
Operation
Fig.5
Fig. 6
Central Heating Mode
To be able to supply heating, the main switch
23
(fig. 5) must be in
I
position. This will be confirmed by the green indicator light
27
(fig. 5.) Turn the temperature control knob
25
clock wise to
establish the green heating indicator
33
(fig. 5).
When there is a demand for heating (either from the room
thermostat or the clock) and the boiler temperature control is
calling for heat. The pump starts allowing the ignition sequence to
begin. The first stage solenoid
a
(fig. 6) and safety solenoid
c
(fig.
6) 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
28
(fig. 5) will
light. After 45 seconds the second stage solenoid
b
(fig. 6) opens
to allow the full gas rate. If a flame is not detected, after 8 seconds,
the security solenoid closes and shuts off the gas. The red lockout
indicator bulb
29
(fig. 5) will show.
The central heating flow temperature is controlled by the central
heating control thermistor
e
(fig. 6). The boiler has been designed
to minimise cycling and will not attempt to relight for at least 3
minutes after the boiler thermostat has been satisfied (it is possible
to reduce the time to 30 s if necessary). When the room thermostat
is satisfied the burner will switch off and the pump will remain
running for a further 4 minutes before it to stops.
NB :
It is possible to override the 3 minute delay by pressing the
RESET button
30
(fig. 5).
a b c
d
e
I
reset
32
31
30
23
25
33
26
24
27
28
29
f