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Reco-Boxx ZXR / ZXA / Flat – Operation and maintenance instructions
[03/
2022 ]
6.5 Frost protection
HEATING
COIL
The frost protection function is always active if the heating coil has been correctly configured in the prod-
uct setup. The monitoring function uses the temperature sensor T7 for the integrated coil (IBA) or for the
external coil (EBA). The function is activated when the temperature of the coil drops below 4 C. Under
these conditions the pump output is activated and the threeway valve output will be 100% and the unit
will shut down and generate a frost alarm.
PLATE HEAT EXCHANGER (PX)
There are three strategies to protect the plate heat exchanger from freezing:
• 1 - Reduced supply air flow:
The heat exchanger is supplied with a frost protection sensor on the exhaust air (T3). If the exhaust air
temperature (T3) is >1°C and <+5°C:
• In airflow control mode and demand control, the supply air flow will modulate between 100% and
33% (AFlow)of the setpoint (AFn)
• pressure control mode, the supply air pressure will modulate between 100% and 50% (AFlow) of the
setpoint (AFn)
If the exhaust air temperature (T3) is <1°C, the supply air fans will stop until the exhaust air temperature
(T3) is >2°C for 5 minutes.
• 2 - Modulating bypass:
The modulating bypass is controlled by the exhaust temperature sensor (T3). If:
• Exhaust temperature (T3) >+1°C: bypass closed or controlled by free cooling function
• Exhaust temperature (T3) ≤ +1°C: bypass will modulate for the exhaust temperature (T3) to exceed
+1°C.
The corresponding supply air temperature will drop due to a lower airflow through the heat exchanger.
• 3 - Electrical preheating coil (accessory):
If an electrical pre-heating coil EV (KWin) is installed and configured, the pre-heating coil (KWin) will
modulate so the exhaust temperature is +1°C.
• 4 - Differential pressure measurement (Cold climate option):
For cold climate conditions (≥-20⁰C), the unit is equipped with a differential pressure sensor mounted
on the heat exchanger. The pressure sensor detects when the pressure drop, due to frost, has become
too high. In critical conditions, the supply air flow will be paused for a short time, to allow for defrost-
ing.
The frost protection strategy (down regulation supply airflow, modulating bypass or electrical pre-
heating) will still be used as a first step. The defrost function will only be active if the frost protection
strategy is not sufficient.
These Settings can be configured in ADVANCED SETUP
