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T-Product · BCU 465 · 2006 April
Safety Considerations
Safety period
If the start-up signal (terminal #4)
is applied momentarily, the burner
control unit will cycle through the
start-up sequence and then shut
down the burner.
This is to avoid the introduction of
unburned fuel into the combustion
chamber.
Safety Interlock (Limits)
All system safety interlocks must be
hard-wired in series and connected
to terminal #5 of the BCU.
(Example: High gas, low gas, low air
and high temperature limits). In the
event of a loss of any system limit,
terminal #5 must be de-energized.
Low fire delay time (parameter
36)
If the gas is controlled with an air/fuel
ratio regulator cross-connected to
the burner air supply piping, this time
may be factory set up to 5 seconds
on demand.
This ensures the burner is at low fire
before switching off when operating
in an off-low-high-low-off control
system.
Caution:
It is recommendedto use
only with cross-connected air/gas
ratio regulator! When air/gas ratio
regulator are not used it is possi-
ble to have the gas valve open the
air valve closed and maintainflame
supervision. This may result in a
hazardous and explosive mixture.
Use of UVS 6, UVS 8 detectors
in continous operation
If UVS 6 or UVS 8 UV detectors are
used in applications for continous
operation. Parameter 35 should
be set to 1. This forces the BCU to
shut down once every 24 hrs to self-
check the UV detectors.
Reset limit
In order to prevent an automatic re-
set from PLCs or excessive resetting
by customers without monitoring the
burner, a reset limit of 5 resets in 15
minutes is given. After 5 resets, a
flashing
10
is shown as a warning.
The BCU must be reset directly at
the front panel of the device.
Operation of firing systems
at temperatures above
1400 °F (760 °C)
(Flame management bypass)
The burner control unit BCU 480
provides a fail-safe digital input “D1”
(terminal #6) that can be configured
in factory as a flame management
bypass (see also ”Factory Options”
and “Additional Features”). This input
offers the special “high temperature
operation” function. When the digital
input is energized the burner con-
trol unit switches to the HT mode
of operation.
If firing systems are operated at tem-
peratures above 1400 °F, they are
known as high temperature systems.
The flame must be monitored until
the furnace temperature has ex-
ceeded a level of 1400 °F (refer to
NFPA 86-2003 Edition, chapter 7–8
and 7–17). To ensure the reliability of
the system, they are often designed
without flame control. This prevents
erroneous flame signals from caus-
ing faults, for example on a UV sen-
sor that interprets the reflection of UV
radiation as a flame simulation.
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System Design Information
