Carel uChiller UCHBP00000200

70
ENG
µchiller +0300053EN rel. 2.2 - 14.12.2021
Functions
5.14 Free cooling
The free cooling (FC) function can be enabled only on chiller units. The type of free cooling is confi gured by parameter, and may
be:
• air free cooling, on air/water units equipped with air- water heat exchanger coils upstream of the condenser coils and with
modulating fan control;
• remote air free cooling (see the specifi c paragraph);
• water free cooling, on water/water units with mixing of the source water or via water- water heat exchanger upstream of the
evaporator and a 3-way modulating valve on the free cooling circuit.
User Code Description Def Min Max UOM
S U068 Free cooling: enable 0/1=no/yes 001-
S U069 Free cooling: activation diff erential 3.0 0.0 99.9 K
S U070 Free cooling: hysteresis 1.5 0.0 99.9 K
S U071 Design free cooling delta T 8.0 0.0 99.9 K
S U072 Water free cooling: valve closing threshold 5.0 -999.9 999.9°C °C
S U073 Water free cooling: valve closing diff erential 3.0 0.0 99.9 K
M U074 Free cooling type: 0=Air 1=Remote coil 2=Water 0 0 2 -
Free cooling is enabled when the outside source temperature is suffi ciently lower than the temperature of the water entering
the unit, as shown in the following fi gure:
300053_066_R01
DT
SP
FC
OFF
ON
T
emp
Key
FC Free cooling
DT Hysteresis
SP Activation diff erential
Temp User return temperature - outside source temp.
Fig. 5.u
On air/water units, the fans are controlled based on the condensing temperature as long as the circuit’s compressor is on; as
soon as the compressor stops, the free cooling fan is controlled so as to maintain the desired water temperature set point.
5.15 Types of free cooling
5.15.1 Condensing unit with common air circuit
Free cooling is enabled based on the comparison between the user return water temperature and the outside air temperature;
this directly controls switching of the three-way valve, which allows the water returning from the user terminals to fl ow through
the free cooling coil before entering the evaporator. Free cooling capacity is controlled by modulating the fan speed (with the
compressors off ); in combined operation (free cooling + mechanical cooling), fan speed is controlled so as to correctly manage
the condensing stage.
Inputs used:
To enable free cooling:
• User return temperature;
• Outside air temperature;
To manage capacity in free cooling mode:
• (according to the control probe used) Return/delivery water temp.
Outputs used:
• 0-10 V to manage the common fan between free cooling and condenser;
• Free cooling valve On-Off control.