Worcester ZWBR 7-28 HE plus

6 720 610 597 GB (01.07)
Appendix
51
10.7.2 Central heating function Fig. 61
Mains
switch
ON.
Fan min.
speed for
90 secs.
Green
light
ON.
Burner lights.
Red light ON.
Ignition spark for
5 seconds.
Fan runs to purge
gas from burner.
Repeats 5 times
before lock-out.
Room thermostat
and/or mains
programmer or
link ON
AND
Electronic facia
programmer
(if fitted) ON
AND
CH control knob
ON.
CH
demand.
Pump ON
Fan to
start speed.
Gas valve opens.
Burner
stabilises at
start speed
for 5-10 secs
Fan speed
reduces
over 15
secs.
Gas valve
closes.
Red light
OFF.
*
Minimum
heat input
for 15min.
Boiler
operates to
match
system load
and CH
control
setting.
Boiler
unused for
long
period.*
Over temperature
shut-down if water
temperature is 5°C
above set value.
Burner remains OFF
until flow temperature
is below set value.
Gas valve shuts.
Pump remains ON.
Pump and Fan
run for upto
3 mins.
CH demand
satisfied.
Yes
No
Yes
No
* NOTE: The sequence ensures that the condensate siphon is not empty
after long
OFF
periods. (More than 24 hours without a demand).
Ignition sequence
ce
6 720 610 576 - 25.1O