Energy Recovery - Carrier 39HXC Manual

3 - FEATURES
Air intake fan
104
Air intake fan
105
106

3.8 - Energy recovery

3.8.1 - Recovery operation
The unit has a variable speed rotary heat exchanger or a plate heat exchanger. This is used to heat fresh air in winter or cool fresh air
in summer.
Energy recovery (rotary heat exchanger started up or plate heat exchanger bypass closed) starts under the following conditions:
- If the heat recovery unit heating requirement is greater than 0% and the return air temperature is higher than the fresh air
temperature + difference P225
- If the heat recovery unit cooling requirement is greater than 0% and the return air temperature is lower than the fresh air temperature
- difference P225
- During the ventilation start-up phase
If there is a free cooling or night cooling requirement, the recovery is stopped. There are temperature hystereses to prevent inadvertent
starts/shutdowns.
The rotary heat exchanger can be forced to shut down using parameter P158 (accessible via BMS)
158
225
Heat recovery unit
requirement
3.8.2 - Heat recovery defrost
Heat recovery unit frosting is monitored as standard via the fresh air temperature, or optionally using a differential pressure sensor
(P37).
37
With preheating coil
There may be an electric heater to prevent frosting of the heat recovery unit.
If there is a pressure sensor, a 5-minute preheating cycle is activated once the pressure difference on the heat recovery unit is above
the threshold (P328).
Otherwise, monitoring is carried out via the fresh air temperature sensor. In this case a one-hour preheating cycle is activated once
the fresh air temperature drops below the threshold (P227).
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220
221
227
328
Without preheating coil
In the absence of a preheating coil or if the coil is unavailable (faulty or load shed), the heat recovery unit bypass is opened 80% (for
a cycle 10-minute cycle), or the rotary heat exchanger (for a 5-minute cycle) set to minimum speed, once the pressure difference on
the heat recovery unit is above the threshold (P328) or the fresh air temperature is below the threshold (P227).
226
Air intake ventilation control
Air extraction ventilation control
Multiplication factor value of the signal sent by the air extraction fan with pressure control in the supply air
duct
load shedding of rotary heat exchanger
Temperature difference for heat recovery unit run authorisation
Cooling > 0%
None
Heating > 0%
Free cooling Night cooling
Differential pressure sensor on the heat recovery unit
Electric pre-heater
Heat recovery unit min. flow rate pressure drop threshold
Heat recovery unit max. flow rate pressure drop threshold
Heat recovery unit frost protection temperature threshold
Heat recovery unit pressure drop calculated threshold
Gradual speed heat recovery unit min. speed
Temperature
Return < fresh air –P225
On
Off
Off
Off
Return air > fresh air + P225
Off
Off
On
Off
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