Operational Flow Diagrams - Worcester 35CDi Installation And Servicing Instructions

17. Operational Flow Diagrams

CENTRAL HEATING FUNCTION
MAIN SWITCH
CH light On.
Pump On.
Fan high
CENTRAL 2 second then
HEATING Low Speed.
DEMAND Ignition
Sequence.
Burner Light
on
Three minute
wait
DOMESTIC HOT WATER FUNCTION
MAIN SWITCH
ON
HW light On.
Pump On.
DOMESTIC Fan high
HOT WATER 2 Seconds
DEMAND then Low
(Priority over Speed.
CH demand) Ignition
Sequence.
Burner on
Ten second
wait
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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
Fan Speed
Change at
Approx mid
pressure
Gas valve Off.
(HW light still
on. Pump still
On)
27
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 DEMAND
temperature END
set by control
knob
Over tempera-
ture shut-
down if flow
temperature
5°C above set
value
Flow switch
On
(Tap open)
Modulate gas
to maintain
delivered
DEMAND
water
END
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
85°C
(until 74°C)
Pump
continue four
minutes.
Fan continue
fifteen
seconds
Fan continue
fifteen
seconds
Possible
overrun
condition
within next
four minutes
(See next
section)