Direct Digital Controller
112 Direct Digital Controller fw 4.013 – Ed. 01/2013
• Indicatively, a system that uses floor radiant heat exchangers will use "low" slope values, a fan coil system
will use “medium” values and a system with radiators "high" values
• Set the Offset parameter at 0.
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:
• Internal ambient temperature higher when the external temperature is higher: in this case the slope is
insufficient, set a higher value for the slope parameter.
• Internal ambient temperature higher when the external temperature is lower: in this case the slope is
excessive, set a lower value for the slope parameter.
If, however, the slope is correct (internal environment temperature stable on variation of the external
temperature), but the internal temperature does not coincide with that set as set-point, the following cases may
occur:
• Internal ambient temperature still higher than the set point: in this case, intervention must be made on the
Offset parameter of the climatic curve, setting a negative value equal to the offset of the internal
temperature from the set-point; for example, if the set-point is 22 °C (71,6° F) and the effective internal
temperature is 26 °C (78,8° F), set the Offset parameter at a value of -4 °C (-7,2° F).
• Internal ambient temperature still lower than the set point: in this case, a positive value must be set for the
Offset parameter of the climatic curve; for example, if the set-point is 20 °C (68° F) and the effective
internal temperature is 19 °C (66,2° F)., set the Offset parameter at a value of 1 °C (1,8 ° F).
Figure 22 –GRAPHICS OF THE “HEATING CURVES”
Curve for internal environment
T = 20 °C (68° F)
External environment T
Water T
°F
212
194
176
158
140
122
104
86
68
68 50 32 14 -4 -22 °F
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