PFU 780 · Edition 02.12l
53
Project planning information
6 .7 Fault message
The fault signalling contact opens, as soon as the mains
voltage 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
57 (Socket 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.