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Access 4.x |
Free cooling |
Free cooling is used during the summer to cool the building at night-time using cool outdoor air.
Installation of outdoor and room temperature sensors is required. Alternatively, intake air and extract air temperature sensors can be used.
In that case, the function performs temporary starts of the AHU (default: 3 min run every 60 min) for temperature sampling.
Operation will continue if measured temperatures fulfill the condition for running. Otherwise the operation will stop after 3 minutes and retry after 1 hour.
Free cooling is only activated when all conditions are fulfilled:
- The unit is stopped by the schedule.
- The unit is scheduled to run in next 72 hours.
- Less than four days have passed since the unit was last in running mode.
- The outdoor temperature during the previous running period exceeded a set limit [22] °C.
- Current outdoor temperature is within permissible limits [10] > Outdoor temperature < [18].
- Current room temperature is > [18] °C.
- Current time is between 00:00 and 07:00.
When free cooling is active, the fans run at normal speed or the set value for pressure/flow control. An offset can also be entered for the fan setpoints during free cooling.
After free cooling has been active, the heating output is blocked for [60] minutes.
Settings and configuration of Free cooling |
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Variable |
Available options & Selection |
Note |
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Activate Free cooling function |
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Configuration > Functions > Function activation |
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Free cooling |
| Yes | No | |
- |
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Activate temperature sensors |
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Configuration > Functions > Temperature control |
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Room temperature sensor |
| No | 1 | 2 | 3 | 4 | |
alternative: Extract air temperature sensor |
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Outdoor temperature sensor |
| Intake air | Outdoor | Outdoor + Intake air | |
alternative: Intake air temperature sensor |
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Configure inputs |
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Configuration > I/O allocation settings > Analog inputs > |
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Room temperature 1 |
Any available I/O |
- |
|
Outdoor temperature |
- |
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Operational settings |
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Data & Settings > Demand control > Free cooling |
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Free cooling mode |
Not active | Active |
Indication of function status |
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Running when day outdoor temperature > |
[22] oC |
Settings for run condition check |
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Stop when night outdoor temperature > |
[18] oC |
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Stop when night outdoor temperature < |
[10] oC |
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Stop when room temperature < |
[18] oC |
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Free cooling start hour |
[0] |
Free cooling is activate during period 0:00 - 7:00 |
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Free cooling stop hour |
[7] |
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Time to block heat output after free cooling |
[60] min |
Heating is blocked after free cooling for 60 min. |
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Fan-kick temperature check |
[180] s |
Only work if: Intake air is used instead of Outdoor air sensor and/or Extract air is used instead of Room temperature sensor. Fans start for 180 s every 60 min to allow sensors to measure the temperatures |
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Fan-kick interval time |
[60] min |
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Configure fan offset |
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Data & Settings > Fan control > Fan setpoints |
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Offset supply air fan when free cooling |
[0] Pa |
- |
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Offset extract air fan when free cooling |
[0] Pa |
- |
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Chapter info
Last reviewed: 11/29/2021
Access version: 4.6-0-14 (3045)