Fridgewatch 2100 Controller Mk4
Publication 3-58
Section 3
Page 118 of 152
Issue 1.1 : 01/08
It is important that during commissioning the value of S94 is set
appropriately for the system. If too many unload pulses are generated,
the pressure will rise above the S95 value. The PID loading algorithm
that has been suppressed whilst below the Hold Limit will cause the
compressor to load again and the cycle will repeat. The system will yo-yo
in and out of limiting causing unstable control. If too few unload pulses
are generated the trip setting S97 is more likely to be reached.
S98 Estimated number of pulses to move slide valve from
minimum to maximum position (for compressors without an
LVDT or slide valve position switches)
NOTE: if an LVDT or slide valve position switches are
fitted, refer to Table 13 and Table 14, use S98 = 0 and
S99 = 0 and ignore the following paragraphs.
The Fridgewatch 2100 Controller uses setting S98 to estimate whether
sufficient successive load pulses have been issued to move the slide
valve to the maximum load position for compressors with no slide valve
position detectors fitted.
S98 should be set to the number of load pulses required to move the
slide valve from minimum to maximum position under normal operating
suction and discharge gauge conditions.
During commissioning first set S98 and S99 to high values, for example,
30. Then try different values of the Load Pulse Duration (S101 or S103
or S105 as appropriate) so that when running under normal operating
suction and discharge gauge conditions, a 'reasonable' number of pulses
are required to move the slide valve from minimum to maximum load. A
suggested value to aim for is 15 to 25 pulses. S98 is shared by all
compressors controlled by one FW2100 panel so the Load Pulse duration
timer settings must be adjusted for individual compressors so a single
value of S98 is acceptable for all the compressors.
After adjusting the pulse duration timer, the resulting counted number of
pulses to move the slide valve from minimum to maximum should be
entered into S98.
NOTE: remember during commissioning use motor
current or some other system parameter to estimate
slide valve position - DO NOT use the Min/Low/High/Max
indicators on the Fridgewatch 2100 front panel.
S99 Estimated number of pulses to move slide valve from
maximum to minimum position (for compressors without an
LVDT or slide valve position switches)
NOTE: if an LVDT or slide valve position switches are
fitted, refer to Table 13 and Table 14, use S98 = 0 and
S99 = 0 and ignore the following paragraphs.
The Fridgewatch 2100 Controller uses setting S99 to estimate whether
sufficient successive unload pulses have been issued to move the slide
valve to the minimum load position for compressors with no slide valve
position detectors fitted.
S99 should be set to the number of unload pulses required to move the
slide valve from maximum to minimum position under normal operating
suction and discharge gauge conditions.
