Operational Flow Diagrams - Worcester 24CDi BF Installation And Servicing Instructions

18. Operational Flow Diagrams

CENTRAL HEATING FUNCTION
MAIN SWITCH
CH light On.
Pump On.
CENTRAL
Ignition
HEATING
Sequence.
DEMAND
Burner Light
On.
Three minute
wait
DOMESTIC HOT WATER FUNCTION
MAIN SWITCH
ON
DOMESTIC HW light On.
HOT WATER Pump On.
DEMAND Ignition
(Priority over Sequence.
CH demand) Burner on
Ten second
wait
Green Light
ON On
Two minute
minimum
burner
pressure then
ramp up
pressure over
next one
minute
Gas valve Off.
(CH light still
on. Pump still
On)
Green Light
On
Four second
ramp to max.
gas pressure.
Gas valve Off.
(HW light still
on. Pump still
On)
Room
thermostat
and/or mains
programmer
(or link) On
AND
AND
Electronic
facia
programmer
(if fitted) On
AND
AND
ST13 link in
AND
AND
CH control
knob On
Modulate gas
to maintain
flow
temperature
set by control
knob
Over tempera-
ture shut-
down if flow
temperature
5°C above set
value
Flow switch
On
(Top open)
Modulate gas
to maintain
delivered
water
temperature
at value set by
control knob
Over
temperature
shut-down if
water
temperature
8°C above set
value
Burner shut-
down if
primary
temperature
94°C
(until 84°C)
27
Pump
DEMAND continue four
END minutes.
Possible
overrun
condition
DEMAND
within next
END
four minutes
(See next
section)