Air Monitoring During Pre-Purge - Honeywell BCU 370 Technical Information

Parameters

4 .5 .3 Air monitoring during pre-purge

Parameter 04
This parameter is activated automatically if parameter
05 "Air monitoring during operation" has also been acti-
vated. The parameter determines whether the air supply
is monitored during pre-purge.
To ensure that there is actually air pressure during pre-
purge, the pressure can be monitored using the air
monitoring during pre-purge function.
Parameter 04 = 0: no air monitoring during pre-purge. A
decrease in the air pressure or a failure in air supply will
not be detected.
Parameter 04 = 1: air monitoring during pre-purge. Air
pressure switch signal to terminal DL (7). The BCU
checks whether the air monitor signal changes:
– Check of the LOW signal (no air monitoring signal)
Before pre-purge, no signal may be present. A LOW
signal must be applied to input DL. If the LOW signal
is not applied, the BCU performs a fault lock-out once
the delay time of 25 seconds has elapsed. Fault mes-
sage: 0 , "no flow" state check.
– Check of the HIGH signal (air monitoring signal acti-
vated)
Once the fan has been activated, the BCU checks
whether the air monitor switches while the actuator
moves to the Open position (start-up with pre-purge)
or during the waiting time (quick start). The signal to
input DL must be switched to HIGH. If the HIGH sig-
BCU 370 · Edition 01.19
nal is not applied, the BCU performs the set number
of further start-up attempts (parameter 07) after a
delay time of 25 seconds has elapsed. If no further
start-up attempts have been parameterized, a fault
lock-out occurs and fault message 1 , "No air supply
during start-up", is displayed.
Air pressure must be present and a HIGH signal must
be applied to input DL during the subsequent pre-
purge. If the HIGH signal is not applied, the BCU per-
forms a safety shut-down once the delay time of 25
seconds has elapsed. If no further start-up attempts
have been parameterized (parameter 07), a fault lock-
out occurs and fault message P , "No air supply during
pre-purge", is displayed.
Depending on the application standard, different air
monitoring methods are possible. Along with pressure
monitoring, other functions such as fail-safe feedback
signals from the actuator or air flow monitoring devices
may be required. Please note application standards.
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