Dry Cooling /Condensing Adjustment; Set-Point Management - LU-VE Emeritus LU1W Manual De Usuario

4 DRY COOLING /CONDENSING ADJUSTMENT

Among the different adjustment options that the LU1W controller offers, the most significant are:
•
Set-point management (paragraph 4.1), which can be selected as:
-
fixed set-point
-
floating set-point, variable with ambient temperature
•
Type of adjustment (paragraph 4.2), which may be:
-
Proportional
-
Incremental by neutral zone
Each of these options has advantages according to the type of use intended for the exchanger.
For industrial applications, where it is necessary to maintain the output of a dry cooler or condensing temperature as
stable as possible, with minimal positive or negative deviations from the desired reference, a combination of fixed set-
point and incremental neutral zone adjustment is advisable.
For controlling a remote condenser or a dry cooler at the service of a conditioning system, on the contrary, where the
objective is to lower as much condensing pressure as possible to reduce compressor consumption, it may be useful to
combine a proportional adjustment (which already tends to reduce its condensing pressure) by decreasing the set-
point dynamics based on ambient temperature (up to a user-defined minimum).
It is necessary to highlight the fact that the variable set-point and incremental neutral zone control settings are related
to a time-trend of the ambient temperature and of the adjustment temperature respectively, rather than the
instantaneous value of those variables. As a result, for example:
•
with a proportional setting, with the adjustment temperature equal to set-point, the active resources are
always 100% (maximum ventilation or wet resources at their maximum),
•
with a neutral zone adjustment, even with regulation temperature equal to set-point, the percentage of
resource activation can range from 0% (idle fans) to 100% (maximum resource utilisation).
This is especially important when monitoring the plant.
4.1
The PR02 parameter is the adjustment set-point in the liquid cooling/condensing mode.
The set-point is always defined in temperature: in the case of the condensers, the condensing pressure acquired is
converted to temperature according to the type of refrigerant selected, parameter PH01, to be compared with the
set-point.
You can select a second set-point (winter), parameter PE09, below set-point PR02.
Parameters PR21 (upper limit) and PR22 (lower limit) allow you to limit the cooling/condensing range of set-point
values to prevent possible setting errors.
You can change the set-point in use from PR02 to PE09 via digital input DI2. This feature can be enabled via parameter
PH32; the polarity of the contact can be changed via parameter PH33 (by selecting N.O. logic → contact open = PR02,
closed contact = PE09).
The floating set-point can be selected via parameter PE01 (in cooling/condensing mode, the dynamic set-point is
active with PE01 = Condensing). With this setting, the setting uses a virtual set-point, calculated based on the trend in
the ambient temperature duration, which varies between a set-point of PR02 (summer set-point) and a minimum set-
point of PE09 (winter set-point).
The reference ambient temperature for the cooling/condensing set-point change is given by parameter PE03.
For each PE08 duration in which the ambient temperature remains below the value of parameter PE03, the set-point
decreases with an offset equal to parameter PE02. This happens until the set-point reaches the minimum value PE09.
LU1W - User Manual

Set-point management

31 REV.1.1 – 07/11/2017 - ENG