# FastHeating

## `FastHeating` (FB)

FUNCTION\_BLOCK FastHeating

### Short description

> Activation of a fast heating mode (controlled variable: room temperature)\
> \
> Typical application: Activation of the fast heating mode in the operation of an air handling unit

### Representation

<figure><img src="/files/87aa23f33723b356b2245c6e67fac0c7478dba92" alt=""><figcaption></figcaption></figure>

### Function description

#### General

This function block controls the activation of the fast heating mode (*xEn* = TRUE) by comparing the room temperature *rRoomTemp* with the room setpoint temperature *rSetPtTemp* when the ventilation system is active (*xRegAHU* = TRUE).\
The fast heating mode can also be activated independently via the input *xCoolOutProtectionEn* activated.

#### Enable / disable of the fast heating mode *xEn*

| *xReqAHU* | *rRoomTemp*                          | *xCoolOutProtection* | *xEn* | Notes                                                      |
| --------- | ------------------------------------ | -------------------- | ----- | ---------------------------------------------------------- |
| FALSE     | X                                    | FALSE                | FALSE | Fast heating mode via air handling unit and input disabled |
| TRUE      | > *rSetPtTemp* + **rSwitchOffPoint** | FALSE                | FALSE | Fast heating mode disabled due to room temperature         |
| TRUE      | < *rSetPtTemp* + **rSwitchOnPoint**  | FALSE                | TRUE  | Fast heating mode enabled due to room temperature          |
| X         | X                                    | TRUE                 | TRUE  | Fast heating mode enabled via input                        |

Legend: X = any

### CODESYS

InOut:

| Scope       | Name                   | Type   | Initial |
| ----------- | ---------------------- | ------ | ------- |
| Input       | `rSetPtTemp`           | `REAL` |         |
| Input       | `rRoomTemp`            | `REAL` |         |
| Input       | `xReqAHU`              | `BOOL` |         |
| Input       | `xCoolOutProtectionEn` | `BOOL` |         |
| Output      | `xEn`                  | `BOOL` |         |
| Input Const | `rSwitchOffPoint`      | `REAL` | -1      |
| Input Const | `rSwitchOnPoint`       | `REAL` | -2.5    |


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