20
LOW-TEMPERATURE OPERATION WITH ANTIFREEZE MIXTURE
In the cooling phase, standard units can be operated with a water output temperature of
5°C
.
It is possible to cool fluids
down to a temperature of -10°C
as long as the chilled water
contains enough anti-freeze liquid to prevent freezing inside the evaporator and by using
special low-temperature versions of the unit (consult the nearest UNIFLAIR service
agent).
For low temperature function the settings of the LP pressostat and anti-freeze thermostat are changed and
special low temperature seals are used.
The table below gives the minimum recommended percentages of glycol in relation to the output temperature
of the cooled fluid; it also gives the settings for the minimum pressostat and the antifreeze safety threshold.
Minimum fluid temp. with unit in operation (1)
5 °C
3 °C
0 °C
- 3 °C
- 6 °C
- 10 °C
Percentage (by weight) of ethyl glycol (2)
0%
10%
15%
20%
25%
30%
Antifreeze safety threshold (unit stop)
4 C°
2°C
-1 °C
- 4 °C
- 7 °C
- 11 °C
Freezing
0 °C
- 4 °C
- 7 °C
- 10 °C
- 13°C
- 17 °C
NOTES
:
(1)
If it is necessary to produce liquid at less than -10°C, Uniflair Italia srl must be informed at the time of ordering.
(2)
The dimensions of the pump motors used in standard units permit a maximum glycol percentage of 30%
IMPORTANT: insulate tubes and chilled water connections carefully to avoid the formation of frost.
The percentage of glycol used must reflect the minimum external air temperature of the
installation: see section on WINTER FUNCTIONING.
Before the outside temperature
reaches the freezing point of the mixture the unit’s hydraulic circuit must be drained.
Special units with 30% glycol by weight can function at temperatures down to a minimum
temperature of -10°C, below which the hydraulic circuit must be drained to prevent freezing
.
IMPORTANT WARNING
Standard units are designed for output temperatures down to 5°C. Units with glycoled water can operate with
water output temperatures down to -10°C.
Free cooling chillers must be loaded with antifreeze.
If the optional heating cable is fitted, the electrical power supply must not be interrupted when the unit is
turned off
.
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