Start procedure

The air handling strategy starts, if the plant mode takes one of the values:


Start procedure on initial start-up to prevent frost alarm

On initial start of the air handling unit this macro prevents start-up problems and provides frost protection.


If during start-up the outside air temperature is below 6°C, defined by parameter START-01, the mixed air dampers starts on forced recirculation during the time of the parameter START-04, when the plant mode changes to "occupied period" (4) or "extended operation"(5). The supply air temperature setpoint will be raised temporarily by a value, defined by the parameter START-02, as soon as the period of forced recirculation has elapsed. Then it will be ramped down to its normal setpoint within the time defined by the parameter START-03.


Description

Default value

START-01: limit OAT to start frost protection

6 °C

START-02: supply air temperature setpoint raise

10 K

START-03: SAT control raised setpoint decrease time

600 sec

START-04: period of forced recirculation after start

600 sec


Integral function enable delay after start-up

After the air handling unit has been started, both temperature controllers for room - and supply air temperature, will be only proportional controllers during the time, defined by parameter SAT-04. After the “I-enable” delay, the integral functions will start with a value of “0”, to assure a smooth start-up.


Description

Default value

SAT-04: supply air temp. control I-time

50 sec