Honeywell BCU 370 - 4.3 Behaviour During Start-up

BCU 370 · Edition 01.19 44
Parameters
4.3 Behaviour during start-up
4.3.1 Minimum burner pause time t
BP
Parameter 11
Determines the minimum burner pause time.
To stabilize the burner operation, a minimum burner
pause time t
BP
can be set independently of the central
control system.
If the start-up signal (ϑ) drops after fan start or if a
safety shut-down occurs, a restart is suppressed for the
duration of the minimum burner pause time t
BP
, which
starts to elapse after expiry of the post-purge time t
PN
(parameter 19).
4.3.2 Burner start-up attempts
Parameter 07
This defines the maximum number of possible start-up
attempts of the burner.
For burners which require several start-up attempts
due to longer pipes for example, the BCU can automati-
cally carry out several start-up attempts.
Parameter 07 = 1: one start-up attempt
If a safety shut-down takes place during start-up, e.g.
on account of a flame signal failure, a fault lock-out oc-
curs once the time t
SA
has elapsed. The display blinks
and shows the cause of the fault.
Parameter 07 = 2 – 4: 2 – 4 start-up attempts
If several start-up attempts are set at the works and if
the BCU performs a safety shut-down during start-up,
it closes the valves after the safety time t
SA
has expired
and attempts to start up again. Each start-up attempt
begins with pre-purge. Once the last programmed
start-up attempt has failed, the burner control unit per-
forms a fault lock-out, in case no flame has formed. The
display blinks and shows the cause of the fault.
In accordance with EN 7462 and EN 676 a maximum
of four start-ups are permitted in specific cases if the
safety of the installation is not impaired. Please note
application standards.
NOTE: only 1 start-up attempt is possible for units with
FM or CSA approval.