Bcu Switched Off; Furnace Control; Mains Switch; Note On Ec Type-Examination - Honeywell Krom Schroeder BCU 480 Manual

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6 .19 BCU switched off

In general, the BCU cannot be activated when no mains
voltage is applied or the burner control unit 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.

6 .20 Furnace control

Switch on the system to start up the furnace, then
release the burner start via the safety interlocks and
afterwards start the burner control so that the burner
control unit may monitor the burners as intended. To
shut down the furnace, first disconnect the burner
control unit from the temperature control (burner ON
signal), then disconnect the safety interlocks and finally
switch off the system.

6 .21 Mains switch

The mains switch in the unit isolates the BCU on two
poles from the mains. It does not meet the require-
ments of EN 50156-1:2004 (5.2.2 Switch disconnec-
tors) set out in chapter 5 for a device to disconnect the
power supply.
Although the mains switch cannot be used for discon-
necting from the electrical power supply in accordance
with EN 50156, it does allow the burner to be isolated
BCU 480 · Edition 03.16l
functionally from the central control system. This func-
tion is required for manual operation and, in the case of
PROFIBUS units, to switch off the unit without causing
bus errors.
Disconnection for electrical maintenance work is to be
implemented with an external switch per unit or group
only, in accordance with Standard EN 50156.

6 .22 Note on EC type-examination

Since EN 298 (1993) does not describe all functions of
the BCU, the operator is responsible for ensuring that
all parameters and functions are matched to the re-
spective application.
6 .23 SIL/PL level for thermoprocessing
equipment
Since thermoprocessing installations include different
safety functions, it is not possible to determine a single
SIL/PL level for an entire installation, but this must be
determined separately for every safety function of the
installation.
See also page 76 (Safety-specific characteristic val-
ues).
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