US FLOOR / FLOOR
Minichiller inverter Duo
43
24
OPERATION LIMITS
24.1 Evaporator water flow rate
The nominal water flow rate is referred to a temperature differential of
∆
T=5°C between inlet and outlet of the evaporator. The
allowed maximum flow rate is corresponding to
∆
T=3°C; higher values may cause too high pressure drops. The allowed minimum
water flow rate is the one corresponding to
∆
T=8°C (except for the model US 06 for which the maximum value of
∆
T is 6,25°C.
Insufficient water flow may in fact cause too low evaporating temperatures with the intervention of safety devices for stoping the
operation of the unit and, in some particular cases, the water can freeze in the evaporator coil causing the refrigeration circuit to
break down or causes the increasing of the condensing pressure with the shutdown risk of the appliance and the compressor
could be damaged.
We enclosed below a most accurate table showing the minimum water flow that should be ensured for the plate heat exchanger
in order to have the proper operation of unit as a function of the model (note: the water flow switch is used for preventing the
freezing sensor from failure in the case of insufficient water flow but it does not ensure the minimum flow rate required in order
the unit can work properly).
Model
US
06
09
12
16
Cooling capacity for reference [kW]
5,14
8,33
11,69
13,15
Minimum water flow rate that to ensure [m3/h]
0,71
0,90
1,26
1,41
As a first approach, and in the absence of other detection systems, the proper water flow for getting the best performance from
your unit can be found at maximum speed of the circulator, using the pressure gauges for controlling the pressure difference
between the return and the delivery water on the outside water connections of the unit and make sure that such value is equal or
less than the available head pressure indicated on the curve shown in chapter 17 for the respective models and if it’s necessary
you change the settings (for the related circulator) that are reported in the manual cod. 9120523.xx.
24.2 Chilled water production (summer operation)
The allowed minimum temperature at the evaporator’s outlet is 5°C; for very lower temperatures, the unit should undergo some
necessaries structural modifications and different setting parameters of the controller with micro-processor. In this case contact
our company for the feasibility study and evaluation of changes to be made according to your requests. The maximum
temperature that can be maintained at the outlet of the evaporator is 25°C. In any case, the maximum electrical input occurs for
the heat pump operating mode at a water outlet temperature of 55°C and with outdoor temperature of -10°C.
24.3 Hot water production (winter operation)
Once the system is working at the right temperature, the inlet hot water temperature should not to be lower than 25°C; the
lowest values that are not related to transitional or start-up stages may cause incorrect working operation to the system with the
possible breakdown of the compressor. The maximum outlet water temperature should not exceed 58°C. At this temperature, the
power consumption and the performances in terms of C.O.P. are enhanced when the outdoor temperature is higher than 5°C,
even if the unit is still able to work up to the limit of -15°C.
For higher temperatures than those pointed out, especially if have a concomitant with the reduction of the water flow rate, it may
cause abnormalities to the normal operating of the unit, or the safety devices act in critical cases. The maximum power
consumption of the heat pump alone occurs during the operation with outlet water temperature of 58°C and outdoor
temperature of -15°C.
24.4 Ambient air temperature
The units are designed and manufactured to operate, in summer operation, with the condensate control, with outdoor air
temperatures ranging between -10°C and 46°C. While operating as a heat pump, the admitted outdoor air temperatures range
changes from -15°C to 40°C depending on the water outlet temperature as indicated in the below table.
Operation limits
Water chiller mode
Ambient temperature
Minimum -10°C M46°C
Water outlet temperature
M5°C M25°C
Heat pump mode
Ambient temperature
Minimum -15°C M30°C
Water outlet temperature
M25°C M58°C/+63°C*
Heat pump mode for sanitary hot water
Ambient temperature with maximum water temp. 48°C
Minimum -15°C M40°C
Ambient temperature with maximum water temp. 55°C
Minimum -15°C M35°C
Water outlet temperature
M20°C M58°C/63°C
Herein below are reported the graphics operating limits during the air conditioning and domestic hot water production modes.
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