Direct Digital Controller
114 Direct Digital Controller fw 4.013 – Ed. 01/2013
8 - Turn the knob to scroll the cursor downwards until “Weather Comp parms” is highlighted, and press the
knob to access the screen.
9 - For the cooled water production system set the “Water set-point at ExtT. 25 °C (77° F)” parameter and
“Water set-point at ExtT. 35 °C (95° F) parameter and any “Offset” parameter.
10 - For the hot water production system, set the “Slope” parameter of the heating curve and any “Offset”
parameter.
11 - To exit, select
.
Maximum power limitation
This optional function allows to limit the maximum power made available by the system for the heating and
cooling services, according to the outdoor temperature.
The maximum power installed in a heating or cooling system is dimensioned for the maximum heat load
condition, which can be minimum (in heating mode) or maximum (in cooling mode) project outdoor
temperature.
Therefore, in climatic conditions that are not extreme, the power installed would be over-abundant; especially
in plants with a high number of stages or mixed type (heat pumps plus boilers), more efficient regulation can
be obtained by appropriately limiting the power available, i.e. by preventing the regulator using, also only
temporarily, an excessive number of machines.
In heating mode, the function operates by progressively reducing the number of machines that can be used on
increase of the outdoor temperature. Once activated, three parameters must be appropriately set:
• External temperature at 100% power: set the minimum rated value of the external temperature.
• External temperature at 0% power: the external temperature must be set, over which power in heating
mode is not requested.
NOTE: to prevent limiting the power excessively, it is good practice to insert a margin, setting values slightly
higher that the theoretical ones for these two parameters.
• Enabling delay: with this parameter it is possible to insert an activation delay of the power limiting
function, calculated starting from system switch-on. In this way, it is possible to allow the system to always
use all power available during the system start-up phase.
In cooling mode, the function operates in the same way, clearly with inverted logic with respect to the
variations of the outdoor temperature.
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