PFU 780 · Edition 02.12
52
6 .7 Fault message
The fault signalling contact opens, as soon as the mains vol-
tage fails.
6 .8 Protecting the pilot burner from overload
To protect the unit against overload by frequent cycling, the
maximum number of start-ups per minute is limited for the
PFU. Excessive cycling triggers a fault message (blinking
53
).
The max. number of start-ups per minute depends on the
safety time t
SA
:
t
SA
[s]
Ignition transformer TZI
Max. start-ups/min.
3
5-15/100
6
5
5-15/100
5
10
5-15/100
4
6 .9 Installation
Installation position: any.
Installation in 19” module subracks only, see page 56 (So-
cket connectors)
Install in clean environment ensuring enclosure IP 54 or higher,
whereby no condensation is permitted.
Cable length between PFU and burner: max. 100 m.
6 .10 Wiring
The PFU is suitable for hard wiring only. Do not reverse phase
and neutral conductor. Different phases of a three-phase
current system must not be installed at the PFU. No voltage
may be connected to the valve and ignition outputs.
6 .10 .1 UVS sensor wiring
Connect the UVS sensor directly to the PFU. Operating the
sensor with incorrect polarity or voltage can lead to destruction
of the sensor.
6 .11 PFU switched off
The PFU cannot be activated when no mains voltage is applied
or when it is switched off. The fault signalling contact is only
closed when the unit is supplied with voltage and switched on.
If the unit is switched off, an immediate program abort with
switch-off of all outputs occurs (even during the safety time).
When the unit is switched on, the program run is restarted
in standby.
Project planning information