57
ENG
µchiller +0300053EN rel. 2.2 - 14.12.2021
Functions
5.3.4 Frost prevention
The frost protection threshold on the evaporation temperature is used as the minimum evaporation temperature threshold for
frost prevention. Prevention is applied by limiting circuit capacity when the threshold is exceeded and activating on the frost
protection heater, if confi gured. For details on confi guring the frost protection heater, see the next paragraph, par 5.3.5
Notice: to ensure correct user-side frost protection, at least one probe - evaporation pressure/temperature or delivery water
temperature - must be confi gured. For further details, see par 2.12.5 Disabling frost protection and/or free cooling when no
probe is confi gured.
5.3.5 Frost protection management with two circuits
Frost protection management on Legacy models
The “Legacy” model for backward compatibility allows frost protection control only on the water temperature.
For units with a common evaporator (F003 = 0), frost protection control uses the common delivery temperature and the frost
protection alarm shuts the unit down. If the common delivery temperature probe is not confi gured, frost protection control is
disabled.
For units with two independent evaporators (F003 = 1), frost protection control is managed independently on each circuit. In
this case, the frost protection alarm only stops the corresponding circuit. It can be normal for one circuit to stop due to a frost
protection alarm while the other continues operating, when there are no additional alarm conditions.
Frost protection control uses the water outlet temperature probe on each evaporator.
If no outlet temperature probe is confi gured, frost protection control is disabled
Frost protection management on the standard model
The standard model does not manage independent evaporators (F003 = 0, not modifi able). Frost protection control can be
selected to use the evaporation pressure/temperature or water temperature.
Frost protection control on evaporation pressure/temperature is managed independently on each circuit. The frost protection
alarm only stops the corresponding circuit. Frost protection control uses the evaporation temperature (see par 5.3.1 for further
details). If frost protection control is set on the water temperature, the frost protection alarm shuts the unit down.
If no frost protection control probe is confi gured, frost protection control is disabled
The following table illustrates frost protection management on a case-by-case basis for units with two circuits. For single-circuit
units, management is practically the same, with only the diff erence that the frost protection alarm always shuts the unit down.
µChiller
Frost protection
(U082)
Device Unit status Management
Standard On water and/or
on evaporation
probe
Source
User
OFF Frost protection control is only performed on circuit 1, using the outlet
temperature probe.
When the frost protection threshold is reached, alarm signal A28 is activated.
The heater is activated, where confi gured.
Standard On water User (CH)
Source (HP WW)
ON The standard µChiller does not manage two independent evaporators, each
with its own outlet probe, but rather manages frost protection control using
the common delivery temperature probe, which can only be confi gured on
circuit 1.
Frost protection control only uses this probe.
The frost protection alarm shuts the unit down.
The frost protection heater is activated if confi gured.
Standard On evaporator
probe
User (CH)
Source (HP WW)
ON Frost protection control is performed on both circuits independently, each
with its own evaporation pressure/temperature probe. The frost protection
alarm only stops the corresponding circuit.
The heater in the circuit with the frost protection alarm is activated.
If there are no additional alarm conditions, the other circuit continues
operating normally.
Legacy On water User (CH)
Source (HP WW)
OFF Frost protection control is only performed on circuit 1.
The common delivery temperature probe is used.
The frost protection heater is activated on both circuits.
The frost protection heater and auxiliary heater are activated if confi gured.
Legacy On water User (CH)
Source (HP WW)
ON 1 - Evaporators with common water circuit (F003 = 0)
Frost protection control uses the common delivery temperature probe. The
frost protection heater and auxiliary heater are activated if confi gured.
2 - Independent evaporators (F003 = 1)
Frost protection control is managed independently using the delivery
temperature in each circuit. If there are no additional alarm conditions, the
other circuit continues operating normally. The frost protection heater and
auxiliary heater are activated if confi gured.
Tab. 5.g
Notice:
• The frost protection heater is always controlled based on its position and the unit operating mode, heating or cooling. See
par. 5.6.7
• The second frost protection heater will only be linked to the frost protection control function on the second circuit and will
never be used as the second frost protection stage.
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