Bosch Worchester GREENSTAR ZWB 7-27 HE combi Installation And Servicing Instructions page 47

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