Direct Digital Controller
110
Direct Digital Controller fw 4.013 – Ed. 01/2013
Setting the water thermostating mode (Master DDC only)
This option, contained in the System installation, allows the user to define thermostating mode for hot and/or
chilled water production plants.
Thermostating may be controlled on the outlet or inlet pipes.
Instructions for setting the water thermostating mode follow:
1 - Select from the initial screen to gain access to the main menu.
2 - Select
to gain access to the System installation.
3 - Enter the installer password on the numerical keypad that appears on the display.
4 - Select
“Plants”
from the drop-down menu.
5 - Select the
symbol for two-line cooling/heating plants,
for hot water production plants,
or for chilled water production plants.
6 - Turn the knob to scroll the cursor downward until highlighting
“Base plant part”
and press the knob.
7 - Turn the knob to scroll the cursor downward until highlighting
“Cond/Heat. serv. Conf.”.
8 - Turn the knob to scroll the cursor downwards until “Wat. Thermost. Mode” is selected, and press the knob
to access the screen.
9 - For the chilled water production plant (left column on the screen),
position the cursor on and press the knob to select on the pipe
where thermostating is to be performed (outlet or inlet).
10 - For hot water production plants, in the screen’s right-hand column,
position the cursor on and press the knob to select on which pipe
thermostating is to be performed (outlet or inlet).
11 - To exit, select
.
If the DDC is the Master of two plants, repeat from 5 to 9 for the second plant
Climatic curve parameters
The option present inside the installation menu allows to define the parameters of the climatic curve that will
affect the flow temperature of the hot and/or cooled water.
The climatic curves allow to calculate the temperature of the system water depending on the external
temperature measured and the set-point temperature of the internal environment.
Depending on the type of system, in particular, the type of exchangers (radiators, fan coils, floor radiators,
etc.) and the features of the building, a specific curve must be used, selected from the family of climatic
curves. Moreover, on variation of the internal room set-point temperature, the curve effectively used will be
modified automatically.
The climatic curves used in the PDC for cooling are different from those used for heating and the methods of
selection of the specific curve to be used differ.
As far as the
cooling
is concerned, the climatic curves are a family of straight lines and the choice of curve to
use is done by specifying two points it must pass through: in detail, the temperature that the cooled water must
have at the external temperature of 25 °C (77° F) and 35 °C (95° F) must be specified; for example, in the
graphics stated in Figure 21, the curve selected implies that the machines will produce cooled water at a
temperature of 7° C (44,6° F) when the external temperature is 35°C (95° F) and 10°C (50° F) when the
external temperature is 25°C (77° F).
The curve defined in this way refers to an internal environment set-point temperature of 25 °C (77° F). If the
set-point temperature is different, the system automatically adapts the curve used.
If the slope of the curve selected is not correct, the following cases may occur, to be evaluated during the first
working period of the system:
NOTE
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