FCU 500, FCU 505 · Edition 02.17
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Parameters
12 .4 .4 Air monitoring during controlled air flow
Parameter 32
Air control is activated by actuating the controlled air
flow input (terminal 2).
After a “no flow” state check of the purge air input (termi-
nal 47, optionally terminal 48), the FCU starts the fan.
Parameter 32 = 0: OFF; maximum capacity.
The actuator is moved to the position for maximum
capacity during controlled air flow. The air flow is not
monitored.
Parameter 32 = 1: ON; maximum capacity.
The actuator is moved to the position for maximum
capacity during controlled air flow. The air flow is moni-
tored and taken into account in the subsequent burner
start. If the air flow fails, a shut-down will be performed
in the same way as during pre-purge.
Flow monitoring only works if air monitoring has
been activated in parameter 15 or parameter 35, see
also page 81 (Low air pressure protection) and
page 89 (Air flow monitoring during pre-purge).
Parameter 32 = 2: OFF; controller enable.
The controller enable signal (terminal 56) is issued. The
position of the actuator can be changed using an exter-
nal temperature controller (controlled cooling). The air
flow is not monitored.
Controlled air flow is only possible in standby (with no
start-up signal).
12 .4 .5 Pre-purge time t
PV
Parameter 34
A burner start may only occur if it has been ensured that
the concentration of inflammable components in all
sections of the burner tile and the connected areas and
the flue gas ducts is less than 25% of the lower flam-
mability limit of the fuel gas. A pre-purge is generally
performed to ensure compliance with these require-
ments.
Parameter 34 is used to parameterize the pre-purge
time t
PV
in a range between 0 and 6500 s.
The pre-purge time t
PV
is to be set on the basis of the
relevant application standard (e.g. EN 676, EN 746-2,
NFPA 85 or NFPA 86).
If air monitoring has been activated in parameter
15 or 35, the pre-purge time t
PV
starts as soon as
the air monitor detects an adequate flow for purg-
ing, see page 81 (Low air pressure protection) and
page 89 (Air flow monitoring during pre-purge).
FCU 505 (zone FCU)
The duration of the pre-purge started by the FCU 505
is determined by the FCU 500 (furnace FCU). The
FCU 505 opens the zone’s butterfly valve for purging,
depending on the input signals at terminal 46 and ter-
minal 66.
