# PreRinseOperationValveAnalog

## `PreRinseOperationValveAnalog` (FB)

FUNCTION\_BLOCK PreRinseOperationValveAnalog

### Short description

> Control of the start-up operation of a ventilation system\
> \
> Typical application: Preparing a ventilation system at low outdoor temperatures

### Representation

<figure><img src="/files/f51105f61e075809d5bab29d7066b58d9dddfb0a" alt=""><figcaption></figcaption></figure>

### Function description

#### General

This function block is used to control the start-up operation of a ventilation system depending on the current outside temperature *rOAT* and the current return temperature *rRnT* of the heater circuit.\
It guarantees the defined and effective preheating of the heater circuit before releasing the fans of the ventilation system (goal: prevention of frost damage to the heater circuit).

#### Control

The start-up operation (preheating and control signal ramp) starts with a rising edge (FALSE > TRUE) at the input *xRequest*,\
if the current outside temperature *rOAT* falls below the threshold **rMaxOAT** is below.\
The output *xEn* is activated (= TRUE) and is used to indicate the active start-up operation or to enable the heater pump.\
The control signal *rHeaterY* is fixed to the setpoint / parameter **rYStart** and is used to control the heater valve.

> **Value range for the setpoint / parameter rYStart**
>
> The setpoint / parameter may only take values > 0 %\
> The start-up operation ends after the minimum duration **tMinTime** (Condition: No return temperature sensor is present (*rRnT* <= -20.0 °C)).

The start-up operation ends if the current return temperature *rRnT* falls below the threshold **rMinRnT** is exceeded (Condition: A return temperature sensor is present (*rRnT* > -20.0 °C)).\
The start-up operation can be terminated at any time by the input *xRequest* (= FALSE).\
\
After the end of the start-up operation, a linearly decreasing (start value = *rHeaterY* ) **rYStart**signal ramp with the duration **tRamp** is generated on the control signal - heater valve from start-up operation. While this signal ramp is being generated and during the start-up operation the output *xRamp* is active (= TRUE).\
\
If the duration of the start-up operation exceeds the threshold **tMaxTime**, the fault message for timeout is activated (= TRUE).\
\
At the output *tET* the elapsed duration is displayed during the start-up operation.\
\
In the inactive state (*xRequest* = FALSE) the outputs assume the following states:

| *xEn* | *xRamp* | *rHeaterY* | *tET*      | *xAlarm* | Notes              |
| ----- | ------- | ---------- | ---------- | -------- | ------------------ |
| FALSE | FALSE   | 0.0 %      | Last value | FALSE    | *xRequest* = FALSE |

Legend: X = any

### CODESYS

InOut:

| Scope       | Name           | Type    | Initial      |
| ----------- | -------------- | ------- | ------------ |
| Input       | `xRequest`     | `BOOL`  |              |
| Input       | `rOAT`         | `REAL`  |              |
| Input       | `rRnT`         | `REAL`  | -22.2        |
| Output      | `xEn`          | `BOOL`  |              |
| Output      | `xRamp`        | `BOOL`  |              |
| Output      | `rHeaterY`     | `REAL`  |              |
| Output      | `tET`          | `TIME`  |              |
| Output      | `xAlarm`       | `BOOL`  |              |
| Input Const | `udiMaxTime`   | `UDINT` | 30           |
| Input Const | `rYStart`      | `WORD`  | 80           |
| Input Const | `udiRamp`      | `UDINT` | 8            |
| Input Const | `eMinTimeBase` | eTime   | eTime.Minute |
| Input Const | `udiMinTime`   | `UDINT` | 2            |
| Input Const | `rMinRnT`      | `REAL`  | 30           |
| Input Const | `rMaxOAT`      | `REAL`  | 10           |


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