Version 2.02 15.05.2007
Function of VS 3000
25
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E 2007 - ECKELMANN AG | BERLINER STRASSE 161 | 65205 WIESBADEN | TELEFON +49(0)611 71 03-0 | FAX +49(0)611 71 03-133
If all NT compressor stages of the pack controller addressed are shut down and temperature t
0
of the NT sys-
tem is greater than the t
0
setpoint NT plus half neutral zone, the NT pack controller immediately loads the avail-
able compressor stage having the shortest run time. Loading takes place regardless of all capacity stages poss-
ibly being disabled by limiting of compressor starts. The LT pack controller can demand a maximum of one NT
capacity stage only when the compressors are at standstill. The demand will be ignored if one NT capacity stage
is already in operation.
If a NT capacity stage has been loaded or if a NT compressor is already running or if the actual value of system
temperature t0 is less than the setpoint plus half neutral zone, the LT demand is acknowledged as positive. If
the NT pack controller cannot load a compressor (e.g. due to HP fault of the NT circuit) or if all compressors
have been shut down (e.g. due to suction pressure fault conditions), the demand is acknowledged as negative.
The LT pack controller generates fault report NT Cascade 1 xxx or NT Cascade 2 xxx at the defined Priority 2 if
it receives negative acknowledgment or no acknowledgment
Compressor demand for NT pack controller NT Cascade 1 xxx is not cancelled until temperature tc of the LT
system has dropped to a value less than limit tc ON Comp + dt. Compressor demand for NT pack controller NT
Cascade 2 xxx is cancelled when temperature tc of the LT system drops to a value less than limit tc ON Comp.
The pack controllers do not shut down the compressor until temperature t0 drops below the setpoint less half
neutral zone and the stop delay has elapsed. This is shown diagrammatically in the following illustration:
t
NT Cascade 1
ZNR. 51203 78 130 E0
t
c
NT Cascade 2
Compressor request NT Cascade 1
Compressor request NT Cascade 2
Cancel request NT 1
Cancel request NT 2
(tc OFF COMPR. - tc ON COMPR.)
4
VS 3000 CO Cascade
2
dt =
dt
dt
dt
dt
tc OFF COMPR.
tc ON COMPR.
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