Air Valve Control Pfu; Purge; Cooling In Start-Up Position/Standby; Burner Start - Honeywell Krom Schroder PFU 780 Technical Information

Parameters
4 . 7 Air valve control PFU . .L
Parameter 30, Behaviour of the air valve during opera-
tion
Parameter 31, Behaviour of the air valve during start-up
Parameter 32, Behaviour of the air valve in the event of
a fault lock-out
The PFU..L features an adjustable air valve control. The
display shows that purging is currently being carried
P 0 A
out with . indicates that the air valve is being ac-
tivated for cooling or heating.
The PFU..L supports the following functions:

– Purge

– Cooling in start-up position/standby

– Switching of the burner between low and high burner
output during operation via the air valve
– To start up the burner as intended, external activation
of the air valve can be blocked during start-up (pre-
vents synchronisation problems between the PFU
and the central control system)
– Controlling the air valve so that it
– opens with valve V2,
– opens once the main burner has reached its operat-
ing position
– Low fire over run time t
PFU 780 · Edition 02.12l
after a normal shut-down
KN
4 . 7 .1 Purge
Parameter 42 = 0: The air valve is closed when voltage is
applied to terminal 30e.
Parameter 42 = 1: The air valve is opened when voltage
is applied to terminal 30e.
In the case of multiple burner applications, burners with
mechanical combustion air supply are used. The air for
combustion and pre-purge is supplied by a central fan
controlled by a separate logic. This logic determines the
purging time.
The PFU..L supports centrally-controlled pre-purge or
post-purge. The PFU..L is informed that purging is cur-
rently being performed by input 30e. It then opens the
air valve, regardless of the status of the other inputs
(purging has priority). The display indicates
PFU 780..K2: For purging, the safety interlock (limits)
must activate input 26e and input 30e of the PFU.
4 . 7 .2 Cooling in start-up position/standby
The air valve can be activated externally via input 10a
for cooling in the start-up position. During activation of
the air valve the display shows
ing is currently being carried out.

4 . 7 .3 Burner start

Parameters 30 and 31 determine the behaviour of the
air valve during burner start.
P 0
.
A 0
, indicating that cool-
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