Appendix
Notes on air pressure monitor
Note on operation
with re-circulation control elements
Interconnection of
The air pressure monitor is checked during starting to see whether it has
the air pressure monitor
dropped out. For this reason it must not be connected in series with other
switching elements which, because they are themselves opened in the rest
position, cause the FMS to incorrectly detect a drop-out air pressure
monitor signal, although the air pressure monitor may actually be making
contact (e.g. series connection with normally open contacts of the fan
protection).
Parameterisation of the
The pre-ventilation time of the re-circulation ducts, in proportion to the
re-circulation pre-ventilation time
boiler pre-ventilation time must be set as a function of the ratio of the boiler
volume to that of the re-circulation ducts and of the quantity of pre-
ventilation air.
(For details, see the latest version of the Technical Regulations on
Steam Boilers [TRD] )
On the FMS this ratio can be set by means of parameter 785
(pre-ventilation time) and 427 (re-circulation release delay).
At the same time the total pre-ventilation time (i.e. boiler pre-ventilation time
alone + boiler and flue gas duct pre-ventilation time) is entered in
parameter 427.
The content of parameter 427 is therefore always < content of
parameter 785.
Example:
Parameter 785 (total pre-ventilation time)
= 50 seconds
Parameter 427 (re-circulation delay time)
= 15 seconds
- Air control elements open. When all are open
the pre-ventilation time starts to run.
- After 15 seconds the re-circulation ducts automatically receive a release
and run open.
The pre-ventilation time is stopped.
- Once the re-circulation ducts have reached their pre-ventilation position,
the pre-ventilation time continues
- After 35 seconds (50 15 ) the pre-ventilation is terminated
S
S
and all ducts close
Interconnection of monitors
If the re-circulation pressure monitor is connected in series with the air
for the re-circulation ducts
pressure monitor, it must be reliably bridged in the starting phase
(to end of T , cf. flow chart) and in periods during which the re-circulation
1
fan is not in operation.
Alternatively, it can also be switched in parallel to the air-pressure monitor
during the startup phase. After the fan starts, it must be correctly switched
in series.
Interconnection
suggestion:
K1 are the contacts of the fan relay, which must be connected
the power contacts.
permanently to
P
P
K1
K1
re-circulation
pressure
monitor
air-pressure
monitor
+24V
FMS
72
9
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