Carel uChiller UCHBD00001230, User Manual

Page: 58 / 108

58
ENG
μc0300053EN rel. 2.2 - 14.12.2021
Functions
5.3.6 Frost protection with the unit
O
FF
When the unit switched off , μChiller provides frost protection: the water is prevented form freezing by activating a pump and/or
frost protection heater. When the water temperature in the heat exchangers reaches the frost protection set point, the selected
device is activated. The probe used is the one located on the user heat exchanger outlet and source heat exchanger inlet. The
following devices can be activated:
• heater;
• pump;
• heater and pump.
The frost protection alarm signal is shown even if the unit is off .
Considering that there is only one digital output per circuit for the heaters, the installation position of the frost protection heater
needs to be selected using parameter U088, between:
• user
• source
• user and source (one digital output for both heaters)
5.3.7 Frost protection heater confi guration
To correctly confi gure the frost protection heater, in addition to setting parameter U088, the digital output also needs to be set
as “frost protection heater”. Only one heater can be confi gured per circuit. For further details also see par. 6.6
User
C
ode Description Def Min Max U
O
M
S U053 Unit OFF: frost protection set point 4.0 -99.9 999.9 °C
S U054 Unit OFF: frost protection diff erential 2.0 0.0 99.9 K
S U075 Frost protection type - 0=Heater 1=Pump 2=Heater/pump 2 0 2 -
S U088 Frost protection heater position - 0 = User 1 = Source 2 = User/Source 0 0 2 -
The frost protection heater is also activated in the event of an frost protection alarm when the unit is ON, after the unit and/or
circuit is stopped.
5.4
C
ompressor rotation
If there is just one compressor, the temperature control request will be exactly the same as the request that the compressor
needs to satisfy. On units with two compressors, μChiller manages rotation in order to balance compressor operating hours and
starts, so as to best deliver the required capacity.
5.4.1 Type of rotation
μChiller starts and stops the compressors based on:
• FIFO rotation (First In First Out), meaning the fi rst compressor to start will also be the fi rst to stop;
• activation time: the fi rst compressor to start will be the one with the lowest number of operating hours.
If the circuit is equipped with a variable-speed (BLDC) compressor, this will always be the fi rst to start and the last to stop.
User
C
ode Description Def Min Max U
O
M
M C048 Compressor rotation type - 1=FIFO, 2=Time 1 1 2 -
5.4.2
C
apacity distribution
μChiller manages the most suitable capacity distribution between the circuits so as to increase overall unit effi ciency. The beha-
viour of capacity distribution varies based on:
• whether there are 1 or 2 circuits;
• the type of compressor(s) used: modulating (BLDC) or fi xed speed;
• the ratio between compressor capacities.
To avoid simultaneous starts or stops of several compressors, there are two fi xed minimum delays: one between starts (30 s) and
the other (10 s) between stops.
Compressor capacity distribution in steps
Below is an example of capacity distribution with two circuits in the tandem confi guration with two fi xed-speed compressors
(scroll), each with the same capacity, and FIFO rotation.