OMEGA AIR A-DRY Series, Installation And Operating Manual, Page: 24 / 65

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The lower limit at 4mA can be selected in range from -100°C to 5°C and the upper limit at
20mA can be selected in range from -60°C to 80°C. Besides, the lower limit at 4mA is always
20°C below the upper limit at 20mA. On the other hand, the maximal measuring range is
100°C. Therefore, setting of lower and upper limits is interdependent.
5.5 Switch Point
The Pressure swing type of dryers uses part of it output air to regenerate itself. The capacity
of the dryer determines amount of compressed air that is used regeneration. The amount is
set for nominal flow at nominal system pressure. In other words, it is set for the worst case.
In fixed cycle mode, dryer timing is set for the worse case. If air consumption is near the
nominal capacity of the dryer, this mode should be selected.
Amount of air for regeneration of a column can be substantial. In case the air consumption is
much less than nominal capacity of dryer, the variable cycle mode can be selected. In this
case, adsorption phase is lengthened. The duration of regeneration is the same, but it takes
place less often. This way, amount of compressed air, which is lost during regeneration, is
reduced. After the long adsorption phase is expired, the columns switch over. The switch
over take place sooner when output dew point, which must be measured, grows above the
switch point.
In the Switch Point Menu, current dew point measurement and switch point threshold are
displayed. This way, we can see if the changeover is going take place soon.
The maximal frequency of columns changeovers is in fixed mode. This frequency can’t be
increased even when the dew point is above switch point threshold permanently. If the
variable cycle is selected although there is no dew point sensor, then the dryer runs in fixed
cycle mode.
5.6 Set Switch Point
It the Set Switch Point Menu, dew point threshold is selected. Besides, fixed or variable cycle
mode is selected in this menu.
***** Dew Point *****
Set Dew Point at
>4mA: -40°C
20mA: 20°C
2 sec.
***** Dew Point *****
Set Dew Point at
4mA: > -40°C
20mA: 20°C
***** Dew Point *****
Set Dew Point at
4mA: -40°C
>20mA: 20°C
***** Dew Point *****
Set Dew Point at
4mA: -40°C
20mA: > 20°C