14: Neutral zone
5-20%
This parameter shows in % how much capacity must be reduced from the setting in eco low
cap to disconnect the economiser.
15: Eco high suct press
-100 to 100°C/R
With ECO operation a suction pressure value can be entered in °C/R. If the suction pressure of
the economiser is above this value, the solenoid valves connected in the economiser system
will be closed. Hysteresis is 2°C/R. In a combined ECO and HLI operation, the set value must
not be above -20°C/R.
16: Unloading (reciprocating compr.)
Normal
Total
Additional steps
VSD Normal
VSD Total
See subsection 3.4.6. Rota (VSD) for more information about the step unloading strategy for
reciprocating compressors with a different kind of coupling; with and without frequency drive.
Select Normal - in general - if the compressor is not equipped with frequency drive and Cen-
ta soft coupling and if the compressor is not equipped with total unload mechanics or with
additional step mechanics. Select Normal for TCMO compressors not equipped with frequency
drive.
Select Total for SMC compressors equipped with total unload mechanics.
When selecting Total the compressor still activates the first capacity steps during start-up -
but during operation (Man/Auto/Remote) it can run down to 0% capacity. In order to avoid
too high oil temperature in this operating mode, there is a 300 second time limit (timer no. 12
Total unload). When this timer expires, the compressor stops.
Select Additional steps for SMC/HPC and CMO/HPO compressors equipped with additional
step mechanics and with an extra solenoid valve for additional steps. SMC 112 and 116 have
two solenoid valves, one is mounted on digital output no. 9 (similar to other compressors with
Additional steps) and the other (valve B) is mounted on digital output no. 3.
Select VSD Normal for SMC and CMO compressors mounted with frequency drive (VSD) and
Centa soft coupling. This choice is made if the compressor should not be able to run totally
unloaded. Never select VSD Normal for compressors mounted with Rexnord coupling.
Select VSD Total for SMC compressors mounted with frequency drive (VSD) and Centa soft
coupling. This choice is made if the compressor should be able to run totally unloaded, i.e. be
able to run down to 0% capacity. Never select VSD Total for compressors mounted with Re-
xnord coupling.
If Normal, Total or Additional steps is chosen for cylinder unloading, Speed is only availa-
ble with Supervisor password.
If VSD Normal or VSD Total has been chosen for cylinder unloading, Step and Speed are
both available with Superuser password.
The VSD cylinder unloading VSD Total also features the ability to run totally unloaded. It
works the same way as with total unloading at fixed speed, i.e. running Total.
Set-up
Engineering manual - Unisab III 1.10
001930 en 2014.09
185/319
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