PFU 780 · Edition 02.12
25
4 .3 Pilot and main burner monitoring
Burner control unit PFU 780 for pilot and main burner combi-
nation of unlimited capacity.
Pilot burner: single-stage-controlled.
Main burner: modulating or stage-controlled.
The burner control unit PFU 780 has separate start-up signal
inputs for the pilot burner (terminal 10e) and the main burner
(terminal 14a). The burner control unit coordinates the program
run (the interplay) of both burners. If required, the main burner
can be started once the pilot burner has reached its operating
position. Benefit: The time for starting up the main burner can
be reduced as low as its safety time. By using two flame ampli-
fiers, the pilot and main burners can be monitored separately.
The PFU 780 can also be used on indirectly ignited surface
burners with end point monitoring.
Three different operating modes are possible:
Permanent pilot burner
t
1
2
ϑ
1
ϑ
2
88
02–04 06–08
04
06–08
04
For applications which require a high system availability or
where a continuously burning flame is necessary. The pilot
burner is ignited once and remains constantly in operation.
The main burner is controlled separately.
Intermittent pilot burner
t
1
2
ϑ
88
02–04 06–08 00 02–04 06–08 00
Pilot and main burners are controlled with one start-up signal
(terminals 10e and 14a in parallel). The main burner starts
automatically after the operating signal from the pilot burner
has been detected. Operation is terminated simultaneously
for both burners.
Interrupted pilot burner
t
1
2
ϑ
1
ϑ
2
88
02–04 06–08
02–04 06–08
The pilot burner is switched off during the main burner safety
time t
SA2
. This type of flame control is required if no distinc-
tion can be made between the flame signals of the pilot and
main burners (e.g. if both burners can be monitored with a
single UV sensor). If the start-up signal for the pilot burner is
applied continually, the pilot burner restarts immediately after
the main burner has been switched off.
Parameters