© Baxi Heating UK Ltd 2008
34
7. Control Sequence
Check
thermistors
give valid
readings
Indicate thermistor fault
Standby
Switched live - ON
On/Off switch - ON
Pump ON
Check
thermistors
read within 8C
Check
casting thermistor
< 76C
APS
Off
Indicate thermistor fault
Indicate circulation fault
Indicate APS stuck fault
Flow temp
< (setpoint -6C)
Flow temp
< 100C
Overheat Lockout
Pre-purge
10 secs.
Fault
condition
> 10 mins
APS On
Flame Off
Indicate false flame fault
Overheat
stat Off
Overheat Lockout
Ignition 5
secs.
Flame On
5 ignition
attempts made
Ignition Lockout
Overheat
stat Off
Overheat Lockout
Run
Check casting
thermistor
< 80C
Casting
temp exceeded
4 times
APS On
Flame On
Air Proving Lockout
APS Off 4
times in
15 mins
Circulation Lockout
Indicate APS fault
Safety shutdown
5 mins
Overheat
stat Off
Check
thermistors
give valid
readings
Switched
live On
On/Off switch
On
Overheat Lockout
Check
flow thermistor
> casting
thermistor
Flow
temperature
< setpoint
Post purge
5 secs
Flow
temperature
> 100C
Flow
temperature
> 100C or
overheat
stat Off
Ignition
attempt or
casting
thermistor
fault
Overheat Lockout
Pump overrun
2 mins
Indicate thermistor fault
Indicate water circulation fault
Indicate false flame fault
No
No
No
No
No
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
Burner
Off
No
No
Go to **
** from
"casting temp
exceeded
4 times"
Yes
Yes
Yes
No
No
No
Fig. 42