Operational Flow Diagram - Worcester 24SiII Installation And Servicing Instructions

17. Operational Flow Diagrams
CENTRAL HEATING FUNCTION
Pump on.
Fan ON/
CENTRAL
ignition
HEATING
sequence.
DEMAND
Burner Light
Three minute
wait
DOMESTIC HOT WATER FUNCTION
DOMESTIC
HOT WATER
Is CH
DEMAND
interrupted?
(Priority over
CH demand)
DHW temp
drops to user
set point
Primary
78°C
MAIN SWITCH
Fifteen second
minimum
burner
pressure then
ramp up
pressure over
On. next one
minute
Gas valve Off.
Burner light
off. (Pump still
On)
MAIN SWITCH
ON
Pump continue
4 seconds if
YES primary temp
above DHW
setting. Burner
to MAX.
NO
Ignition
sequence and
burner to MAX
Gas valve off.
Gas valve off.
Pump on
Room
thermostat
and/or mains
programmer
(or link) On
AND
ON facia
programmer
(if fitted) On
AND
CH control
knob On
Modulate gas
to maintain
flow
temperature
set by control
knob
(50-82°C)
Over tempera-
ture shut-
down if flow
temperature
5°C above set
value
Flow sensor
signal
(Tap open)
Modulate gas
to maintain
delivered
water
temperature
set by control
knob
(40-60°C)
Over
temperature
shut-down if
water
temperature
above 80°C
Primary
temperature
94°C
32
DEMAND Overrun
END function
(see overleaf)
Overrun
DEMAND
function
END
(see overleaf)