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5.5 FROST PROTECTION
HEATING COIL
The frost protection function is always active if the
heating coil has been correctly configured in the product
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
PLATE HEAT EXCHANGER (PX)
There are four 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)
• In 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 (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 defrosting.
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
ROTARY HEAT EXCHANGER (RX)
In order to protect the rotary heat exchanger from
freezing, the strategy for frost protection consists of
modulating the speed of the rotating heat exchanger,
which is linked to the outdoor air temperature (sensor T1).
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temperature of the coil drops below 4°C. Under these
conditions the pump output is activated and the three-
way valve output will be 100% and the unit will shut
down and generate a frost alarm.
If the outdoor air temperature < T°AF (default -9°C): the
rotation speed of the heat exchanger is reduced to avoid
the risk of icing. To exit this anti-frost protection: T°(T1) ≥
T°AF for 5 minutes.
These Settings can be configured in ADVANCED SETUP.
Operation and maintenance instructions
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