In outside temperature-dependent heating circuit control, the setpoint for the flow temperature controller (SpTFl) is calculated via the heating curve depending on the outside temperature and the present room temperature setpoint (SpTR). The flow temperature applicable for heating (TFl) is the manipulated value.

Function overview

In "Heating circuit outside temperature compensated flow temperature control" the following functions are available:

 

Control mode

Intelligent Valve can be operated in 3 operating modes (CtlMod).

The operating mode determines the interpretation of the internal setpoint.

  • Position: The local PI control determines the control valve position
  • Volume flow: The local PI control determines the volume flow of the Intelligent Valve
  • Power: The local PI control determines the power of the Intelligent Valve

 

Heating curve

The heating curve determines the flow temperature setpoint (SpTFl) based on the outside temperature (TOaEff). The curve is parameterized via four setting values:

  • Design outside temperature (TOaDsgn)
  • Outside temperature high (TOaHi)
  • Flow temperature setpoint for design outside temperature (SpTFlDs)
  • Flow temperature setpoint for high outside temperature (SpTFlHi)

Room temperature too high or too low

  • Before you make readjustments:
    If the current room temperature is too high or too low, check the room operating mode. Temporary deviations can always occur, depending on the current operating state.
    Check to find out if the room temperature varies depending on the outside temperature or if it is always too high or too low.
    Does the room temperature vary depending on the outside temperature? If so:
  1. Find out in which climatic conditions the room temperature is not right.
  1. In the Heating curve submenu, readjust the setting to the relevant situation in accordance with the below table.
  1. After the readjustment, wait 1-2 days, allowing the control to settle.
  • Another readjustment may be required

The room temperature is...

Action

...too high in cold weather.

Lower the value SpTFlDs.

...too low in cold weather..

Raise the value SpTFlDs.

...too high in mild weather..

Lower the value SpTFlHi.

...too low in mild weather..

Raise the value SpTFlHi.

 

Heating limit

When the set heating limit (HLm) is exceeded, the heating circuit pump and the supply of heat to the heating circuit are shut down. This saves heating energy at higher outside temperatures.

To achieve this, the function compares the outside temperature (TOa) and the filtered outside temperature (TOaEff) with the heating limit; the heating is suspended when the outside temperature exceeds the limit, and released again, when both temperature values fall below the limit. The heating limit depends on the selected room operating mode.

Exception: In case of an override by the scheduler, the heating will be released independently of the outside temperature, even if it has been suspended before due to a rise in the outside temperature.

 

Room operating mode scheduler

The user can select the desired room operation mode in the scheduler. Three room operating modes are available:

  • Comfort
    • The room temperature is constantly maintained at the Comfort setpoint (SpHCmf).
    • Suitable, when the room is constantly occupied.
  • Pre-Comfort
    • The room temperature is constantly maintained at the Pre-Comfort setpoint (SpHPcf).
    • Suitable, when the room is expected to be occupied shortly.
  • Economy
    • Recommended, when the room is unused for several hours, or a reduced room temperature is desired.
    • Typically the operating mode selected for nighttime.

The setpoints for the three room operating modes can be pre-set.

Heating setpoints

Room operating mode

Setting range

Defaults

Comfort

6...36 °C

21 °C

Pre-Comfort

6...36 °C

19 °C

Economy

6...36 °C

16 °C

 

Optimum start control

The purpose of the optimum start control function is to reach a temperature level of 0.25 K below the Comfort or Pre-Comfort setpoint at the time when occupancy according to the scheduler starts. To this end, the heating circuit has to be switched on at an earlier point in time.

The extent of this time shift depends mainly on the drop in the substitute room temperature, which in turn is directly based on the outside temperature. The warm-up gradient (WarmUpGrdnt) controls the rate of the room temperature increase in K/h (default: 1 K/h).

The function can be (de)activated with EnOscFnct (it is activated by default).

 

Room temperature setpoint shift for boost heating

The purpose of the room temperature setpoint shift function (SpTRShftBstH) is to achieve shorter heating up times. To this end, the room temperature setpoint is raised by an adjustable value while the boost heating is active.

  • Start:
    • Switch of room operating mode
      [Economy or Protection] → [Comfort or Pre-Comfort]
      and
    • The room temperature is more than 0.25 K below the setpoint.
  • SpTRShftBstH default: 5 K

 

Quick setback

The purpose of the quick setback function is to achieve a lower setpoint as quickly as possible when switching the room operating mode.

  • Start: Switch of room operating mode
    [Comfort or Pre-Comfort] → [Economy or Protection]
  • Stop:
    • The room temperature has reached the new setpoint.
      or
    • The room operating mode switches back to Comfort.

While the quick setback function is active, the heating circuit pump is switched off and the valve will close; this is so the room temperature can drop quickly.

Because there is no room temperature sensor, the duration of the setback is calculated based on the substitute room temperature (SbstTR), and thus dependent on the outside temperature (TOa) and the time constant of the building (TcnBldg).

The quick setback function can be (de)activated with EnQckSetbck.

 

Substitute room temperature

The substitute room temperature is calculated based on four values:

  • Pump operation (HcrPump)
  • Outside temperature (TOa)
  • Time constant of building (TcnBldg)
  • Warm-up gradient (WarmUpGrdnt)
    • Default: 1 K/h
    • Setting range: 0.1...10 K/h

Pump on: The temperature rises with the warm-up gradient towards the present heating setpoint.

Pump off: The temperature drops towards the outside temperature. Three times the time constant of the building is used as a filter.

 

Over-temperature protection

This function prevents the secondary flow from rising to an unusually high temperature. The function is always enabled and does not need to be configured.

The pump is shut down if the secondary flow temperature exceeds the present max. value (SpTFlMaxHcr) by more than 15 %. The pump is switched back on once the flow temperature drops below the present max. value again.

 

Flow frost protection

In order to protect against freezing, the flow temperature is monitored on the secondary side (TFl). Frost protection is always enabled and does not need to be configured. The flow temperature setpoint (SpTFl) is set to at least 10 °C if the flow temperature on the secondary side drops below the threshold of 5 °C.

The function stops automatically as soon as the flow temperature has increased to 7 °C. The function is active for at least 5 minutes.

 

Plant frost protection

In order to protect the secondary water pipes against freezing, the plant frost protection function can periodically (10 minutes every 6 hours) or permanently switch on the heating pump based on the outside temperature. This happens independently of the heat demand.

The functions can be (de)activated with EnPltFrPrt (it is deactivated by default).

 

Pump kick

To prevent damage to the pump in off times, it is switched on for short periods of time at regular intervals.

If the pump is switched off for more than 7 days, the kick function periodically switches the pump on for 30 seconds. This means that the selected time corresponds to the switch-off time of the pump the week before, when the first OFF period had started.

The function can be (de)activated with EnKick.

 

Pump operation

The heating circuit pump is running if the application controls to a flow temperature setpoint (SpTFl). It is switched off if one of the following functions responds:

 

Drying function

This function (DrygFnct) ensures controlled drying of the floor. It can control the flow temperature according to a temperature profile, or to a manually set value independent of weather conditions and room settings. The flow temperature max. limitation remains active.

The following setting options are available:

  • [1] Off: The drying function is deactivated. It can also be stopped at any point with this parameter.
  • [2] Constant: The configured value "Flow temperature setpoint for drying constant mode" (SpTFlDrygConM) serves as flow temperature setpoint. The function stops automatically after 22 days.
    • Default: 45 °C
    • Setting range: 20...80 °C
  • [3] Profile: The flow temperature setpoint is controlled by the stored temperature profile. The function stops automatically after 22 days.

 

Maximum volume flow limit

Intelligent Valve is an ePICV (PICV = pressure independent control valve) – i.e. it is fundamental that the maximum volume flow is independent of the current operating mode. The maximum volume flow limitation is always activated.

The setting is done via the object VflMax:

  • Default: Nominal volume flow of the specific valve type V100 = VflNomVlv
  • Setting range: 5…100 % of V100

 

Minimum volume flow limit

The pre-setting of the minimum volume flow is optional and has to be enabled as needed.

  • Default: Inactive
  • Setpoint = 0 → PrVfl = 0

However, a minimum volume flow can be set so that:

  • Setpoint = 0 → PrVfl = X

As follows:

  • Enable volume flow minimum limitation (EnVflMin)
  • Define value (VflMin)
  • Setting range: 2.5...20 % of V100 *) / max. VflMax
    (VflMin cannot be greater than VflMax!)

*)

V100 = Nominal volume flow of the specific valve (VflNomVlv)

 

Maximum power limit

In addition to functioning as an ePICV, Intelligent Valve allows the limitation of max. power to a heat exchanger or user. For this purpose, power control has to be selected.

The design power is defined via:

  • Max. volume flow (VflMax, VflMaxC)
  • Design temperatures for flow (TFlPrimDsgn, TFlPrimDsgnC) and return (TRtPrimDsgn, TRtPrimDsgnC)

Thus, the design power can be calculated as follows:

  • For heating: PwrDsgn = VflMax * (TFlPrimDsgn - TRtPrimDsgn) * c
  • For cooling: PwrDsgnC = VflMaxC* (TFlPrimDsgnC - TRtPrimDsgnC) * c

The power can be limited to the power limitation value (PwrMax,PwrMaxC ) in a range between 0 and the design power.

 

Return temperature limitation

This function controls the primary return temperature at B7 (TRtPrim) according to the set heating/cooling setpoint.

If the return temperature drops below/rises above the limitation value, the present valve control setpoint is lowered. The limitation is supplied by the PI controller; gain (GainTRtCtr) and reset time (TnTRtCtr) can be adjusted.

Defaults

Enable return temperature limitation

EnTRtLm

Inactive

Return temperature setpoint for heating

SpHTRt

40 °C

Return temperature setpoint for cooling

SpCTRt

12 °C

Gain for return temperature controller

GainTRtCtr

1% / K

Reset time for return temperature controller

TnTRtCtr

30 s

The starting conditions are based on whether the controller is operating in heating or cooling mode:

  • Heating mode (B7 < B26): TRtPrim > SpHTRt
  • Cooling mode (B7 > B26): TRtPrim < SpCTRt

The function reduces the calculated setpoint for the valve controller. An already nearly closed valve prevents the return temperature limitation from being enabled.

In order to ensure reliable temperature measurement, the function only closes to a minimum volume flow of 2.5 %.

 

Temperature difference limitation between flow and return (ΔT limitation)

ΔT limitation prevents the primary temperature difference (TFlPrim - TRtPrim) from dropping below a selected setpoint. This counteracts the "low ΔT syndrome", where an oversized valves opens as the load requirement increases. However, the heat exchanger can only transfer a limited amount of heat. This means that for little additional power (Q), the volume flow (V) has to be increased a large amount. The additional pump capacity required reduces the efficiency of the system.

Low ΔT syndrome

If the flow/return temperature difference drops too far, the present valve position is limited. The limitation is supplied by the PI controller, with gain (GainTDiffFlRtCtr) and reset time (TnTDiffFIRtCtr) being adjustable.

Defaults

Enable flow/return temperature difference limitation

EnTDiffFlRtLm

Inactive

Flow/return temperature difference limitation

SpTDiffFlRtLm

6 °C

Gain for flow/return temperature difference limitation

GainTDiffFlRtCtr

2% / K

Reset time for flow/return temp. difference limitation

TnTDiffFIRtCtr

30 s

The function lowers the present valve position. Due to the limited acting range, a nearly closed valve prevent the flow/return temperature difference limitation from being released. To ensure reliable temperature measurement, the functions only closes to a min. volume flow of 2.5 %.

 

Weighted return temperature limitation

This function controls the primary return temperature at B7 (TRtPrim) according to an appropriate "weighted" setpoint for heating and cooling.

Depending on the present volume flow (PrVfl), the function calculates the present return temperature setpoint (PrSpTRt), and if the temperature drops below/rises above the limitation value, the present valve control setpoint is raised/lowered. The limitation is supplied by the PI controller; gain (GainTRtCtr) and reset time (TnTRtCtr) can be adjusted.

Defaults

Enable weighted return temperature limitation

EnTRtLmWgd

Inactive

Design primary flow temperature

TFlPrimDsgn

55 °C

Design primary return temperature

TRtPrimDsgn

40 °C

Volume flow maximum

VflMax

100 %

Gain for return temperature controller

GainTRtCtr

1% / K

Reset time for return temperature controller

TnTRtCtr

30 s

The starting conditions are based on whether the controller is operating in heating or cooling mode:

  • Heating mode (B7 < B26): TRtPrim > PrSpTRt
  • Cooling mode (B7 > B26): TRtPrim < PrSpTRt

In heating mode, the function increases the calculated setpoint for the valve controller. In cooling mode, the function reduces the calculated setpoint.

An already nearly closed valve prevents the return temperature limitation from being enabled.

In order to ensure reliable temperature measurement, the function only closes to a minimum volume flow of 2.5 %.

 

Adapted maximum volume flow limitation

When this function is enabled (EnAdaVflMax), Intelligent Valve limits the adapted max. volume flow PrAdaVflMax.

PrAdaVflMax can take values within an upper and a lower limit:

  • Upper limit: configured value of the manual flow limitation (VflMax)
  • Lower limit: smallest possible manually set limit value V5 = 5 % of V100)

Basically, two types of application are possible:

  1. Application with VflMax = V100
    This type of application is suitable, when the design volume flow is unknown and/or changes frequently. The adapted volume flow max. limitation prevents excessive flow rates without the need to set a value for VflMax.
  2. Application with VflMax < V100
    This type of application is suitable, when the design volume flow is known and only rarely changes. Here, too, the adapted volume flow max. limitation prevents flow rates that are excessive as well as inefficient in terms of energy. Additionally, the manually set flow limitation prevents VflMax from being exceeded at all times.

In operation, the adapted volume flow max. limitation acts as a sliding maximum filter, and calculates the adapted max. limitation value from the measured volume flow values (PrVfl) of the last 4 days. Short-term increases are limited to the value. Longer-term increases (lasting more than 3 hours) lead to a gradual upward adjustment of the adapted max. limitation value (in increments of 3 % of V100 every 3 hours).

During the first 4 days of the calculation, PrAdaVflMax = VflMax applies. The calculation restarts, if:

  • ...the adapted volume flow max. limitation is set from inactive to active.
  • ...the adapted volume flow max. limitation is already active, but the manual flow limitation VflMax is set to a new value.

The following diagram illustrates the functionality of the adapted volume flow max. limitation for the application type VflMax < V100.

V =

Volume flow

t =

Days

 

Adapted maximum power limitation

When this function is enabled (EnAdaPwrMax), Intelligent Valve limits the adapted max. power PrAdaPwrMax.

PrAdaPwrMax can take values between 1 % of PwrDsgn and an upper limit, which corresponds to the configured value of the manual power limitation (PwrMax).

Basically, two types of application are possible:

  1. Application with PwrMax = PwrDsgn
    This type of application is suitable, when the max. power is unknown and/or changes frequently. The adapted power max. limitation prevents excessive power outputs without the need to set a value for PwrMax.
  2. Application with PwrMax otherwise set.
    This type of application is suitable, when the max. power is known and only rarely changes. Here, too, the adapted power max. limitation prevents power outputs that are excessive as well as inefficient in terms of energy. Additionally, the manually set power limitation prevents PwrMax from being exceeded at all times.

In operation, the adapted power max. limitation acts as a sliding maximum filter, and calculates the adapted max. limitation value from the measured power values (PrPwr) of the last 4 days. Short-term increases are limited to the value. Longer-term increases (lasting more than 3 hours) lead to a gradual upward adjustment of the adapted max. limitation value (in increments of 3 % of PwrDsgn every 3 hours).

During the first 4 days of the calculation, PrAdaPwrMax = PwrMax applies. The calculation restarts, if:

  • ...the adapted power max. limitation is set from inactive to active.
  • ...the adapted power max. limitation is already active, but the manual power limitation PwrMax is set to a new value.

The following diagram illustrates the functionality of the adapted power max. limitation for the application type PwrMax < PwrDsgn.

Pwr =

Power

t =

Days

Compensation mode

In volume flow and power control, the flow characteristic can be adapted to the behavior of the heat exchanger transfer. Three characteristics are available: linear, equal percentage, and heat exchanger optimized.

Linear

Recommended for plate heat exchangers water/water or injection circuits in precontrol circuits.

Caps the characteristic at min. volume flow min. limitation

Equal percentage, optimized in the opening range

Recommended for heating and cooling registers where the transfer characteristic is unknown

Modified characteristic with volume flow max. limitation at 60 %

Heat exchanger optimized

Recommended for heating and cooling registers where the transfer characteristic (a-value) is known.

Q = f(V) Heat exchanger characteristic

V = f(Y) Flow characteristic for Intelligent Valve

V̇ =

Volume flow V / V100

Y =

Setpoint

Q =

Heating power

With volume flow max. limitation, the characteristic adapts to the configured limitation setpoint (ex. for an equal percentage characteristic).

With volume flow min. limitation, the characteristic curve is capped below the minimum flow (ex. for a linear characteristic).

Defaults

Characteristic

CmpMod

Linear

Equal percentage (exponential)

Heat exchanger compensation

Linear

Compensation volume flow coefficient

CmpVflCoef

1…4

3

Compensation heat exchanger coefficient

CmpHxCoef

0.1…1

0.3

 

Self-test

A self-test is performed during the hydronic balancing. The self-test can be initiated and stopped via ABT Go or by pressing the SVC button.

  • During this time, the SVC LED flashes blue.

The following criteria are tested, and a corresponding report can be generated:

  • Flow sensor
  • Max. volume flow
  • Differential pressure at max. volume flow
  • Valve position at max. volume flow
  • Leakage rate

 

Forced max. volume flow

This function temporarily overrides the present setpoint. The valve supplies 10 minutes of maximum volume flow (VflMax) when the function is enabled.

  • During this time, the SVC LED flashes yellow.
  • Limitations (return temperature, flow/return temperature difference) are inactive while this function is active.
  • Self-tests are not possible while this function is active.

The function can be started as well as stopped via ABT Go or the SVC button.

 

Valve override mode

In override mode, the setpoint measured at X1 is overridden. Override mode is initiated via ABT Go with the object VovrMod.

  • During this time, the SVC LED flashes yellow.

The following options are available:

  • None
  • Fully open
  • Fully close
  • Minimum volume flow
  • Nominal volume flow
  • Maximum volume flow
  • Design power
  • Maximum power
  • Keep position

Override mode is automatically stopped after 2 hours.