YLAE Units
When changing from fan stage 3 to fan stage 4 all the fan
motors are reconnected from star (slow speed) to delta
(full speed). Similarly when reverting from fan stage 4 to
fan stage 3 all the fan motors are reconnected from delta
(full speed) to star (slow speed). To ensure that arcing
on the contactors are cleared on switching between
states the following dwell times are set:
The transition from stage 4 to 3 requires the following
sequence based on time:
Fan Speed Inhibit
Stage 3 is the maximum fan stage when:
n
the remote fan full speed inhibit contact is closed.
n
if a fan inhibit time period is set under the
'SCHEDULE/ADVANCE DAY' key, and the time of
day is in the 'INHIBIT ON' zone.
Units without Soft Start
The strategy for compressor loading within a system is
to maximize individual compressor run time and ensure
that the same compressor does not start twice in a row.
This is achieved by rotating the lead/lag sequence of the
compressors in a system when a compressor other than
the lag most compressor in that system stops. In
achieving this objective no attempt will be made to
equalize each compressors individual total run hours
within a system.
Units with Soft Start
These units have a soft starter fitted to the last
compressor in each system. SOFT START ENABLED
must be displayed under the 'OPTIONS' key. With this
option enabled the controls ensure that the compressor
fitted with the soft starter is the last compressor to start in
the system. Compressors are always started in the
same order, No1 compressor first.
1
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14
Form 201.26.OI1(11/09)
TIME
1
2
3
STAGE 3
ON
ON
OFF
0
(Transition start)
OFF
OFF
OFF
500 ms
OFF
OFF
ON
1000 ms (Transition complete)
ON
ON
ON
STAGE 4
ON
ON
ON
TIME
1
2
3
STAGE 4
ON
ON
ON
0
(Transition start)
OFF
OFF
OFF
1000 ms (Transition complete)
ON
ON
OFF
STAGE 3
ON
ON
OFF
FAN OUTPUT
