7
5
Fig. 7
Domestic Hot Water Mode
To be able to supply hot water, the selector switch (15 fig.
6) must be in either in
or
position. This will be
confirmed by the green indicator light
(18 fig. 6).
When the cylinder thermostat is calling for heat, it switches
the 3 way valve
g (fig. 7) to hot water position. Then the
hot water from the primary circuit is diverted through the
cylinder coil to heat DHW.
The first stage solenoid
a (fig. 7) and safety solenoid
c (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
(19 fig. 6) will light and the
second
stage solenoid
b (fig. 7) 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
(20 fig. 6) will light.
The hot water flow temperature is controlled by the primary
circuit control thermistor
e (fig. 7).
When the cylinder thermostat is satisfied, the burner is
extinguished and the pump stops.
The boiler will now stay in the hot water mode for three
minutes.
Priority will be given to a demand for reheating the
cylinder.
C
15
16
18
20
17
21
19
22
a
b c
e
Fig. 6
Central Heating Mode
To be able to supply central heating, the selector switch
(15 fig. 6) must be in
position. This will be confirmed
by the green indicator light
(18 fig. 6)
When there is a demand for heating (either from the room
thermostat or the external programmer) and the boiler
temperature control is calling for heat. The pump starts and
at a flow rate of 4 ltr/min the central heating flow switch
operates allowing the ignition sequence to begin. The first
stage solenoid
a (fig. 7) and safety solenoid c (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
(19 fig. 6) will light. After 45 seconds the second stage
solenoid
b (fig. 7) 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
(20 fig. 6) will light.
The central heating flow temperature is controlled by the
central heating control thermistor
e (fig. 7). 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 (this «TAC delay» can be set to 30 seconds if
required, see maintenance and service guide). When the
room thermostat is satisfied the burner will switch off and the
pump will remain running for a further 3 minutes.
NB
It is possible to override the TAC delay by pressing the
cylinder
coil
g
Operation
Summary of Contents for Britony System II Plus 100 Nat
Page 15: ...15 Notes...
