[HCRV] Heating curve

The following diagram illustrates how the flow temperature setpoint is calculated:

The heating curve determines the flow temperature setpoint [SpTFl] based on the effective outside air temperature [TOaEf]. It uses two points on the chart and the radiator exponent [ExpRad]. The coordinates of the breakpoint, the base point for outside temperature [TOaBase] and the average slope [Slpe] of the heating curve are also supplied by HCRV.

Radiator exponent

The higher the radiator exponent [ExpRad], the more the curve deviates from the straight line. The following table illustrates recommended settings for typical heat delivery systems:

Flow temperature setpoint

The flow temperature setpoint [SpTFl] is the setpoint for the automation station logic that controls the flow temperature. Corrections can be made to the flow temperature setpoint to compensate for wind and sun. Solar intensity [SrItyFil] and wind speed [WdSpdFil] are filtered to avoid unnecessary fluctuations to the flow temperature setpoint. A setpoint correction can also be made to the flow temperature at input [SpcTFl]. The minimum and maximum limits for the setpoint can be configured on the inputs [SpTFlMin] and [SpTFlMax].

Connect an outside air temperature sensor

HCRV uses the effective outside temperature [TOaEf] (a combination of filtered values) since the room temperature reacts in a delayed and attenuated manner to changes in outside temperature. The function block HRA can calculate the effective outside temperature.

Input [TOa] must be connected if wind compensation is required.

The outside air temperature high [TOaHi] is limited internally by the temperature setpoint for high outside air [TOaDsgn].

Room temperature setpoint and compensation for wind and solar radiation

Interconnect or set the room temperature setpoint [SpTR] to match the room temperature control or precontrol for room heating groups.

The room temperature increase for nominal solar radiation [DTRSrNom] is the expected room temperature increase at the design outside temperature and 20 °C room temperature if the solar radiation intensity increases from 0.0 W/m² to 1000 W/m².

Set input [DTRSrNom] to 0.0 if the input solar radiation intensity filtered [SrItyFil] is connected, but no compensation for solar influence is needed.

The room temperature decrease for nominal wind speed [DTRWdNom] is the expected room temperature decrease at the design outside and 20 °C room temperature if the wind speed increases from 0 m/s to 20 m/s.

Set input [DTRWdNom] to 0.0 if the input filtered wind speed [WdSpdFil] is connected, but no compensation for wind is needed.

[SpTRNom] is a constant with a value of 20 °C / 68 °F.