Operational Flow Diagrams - Worcester 24ijunior Installation And Servicing Instructions

18. Operational Flow Diagrams

CENTRAL HEATING FUNCTION
Pump on.
Fan ON/
CENTRAL
ignition
HEATING
sequence.
DEMAND
Burner Light
On.
Three minute
wait
DOMESTIC HOT WATER FUNCTION
DOMESTIC
HOT WATER
Is CH
DEMAND
interrupted?
(Priority over
CH demand)
DHW temp
drops to
<55°C
Primary
78°C
MAIN SWITCH
ON
19 second
minimum
burner
pressure then
ramp up
pressure over
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
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
(55°C)
Over
temperature
shut-down if
water
temperature
above 80°C
Primary
temperature
94°C
33
DEMAND Overrun
END function
(see overleaf)
Overrun
DEMAND
function
END
(see overleaf)