Page 14 - IOM / TELECOOL THN - 0104 - E
STARTING UP
CHECKING THE REFRIGERANT LEVEL
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After a few hours of operation, check whether the liquid level
indicator has a green ring: a yellow colour indicates the
presence of humidity in the circuit. In such a case the circuit
must be dehumidified by qualified personnel.
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Large quantities of bubbles should not appear through the
liquid level indicator. A constant passage of numerous
bubbles may indicate that the refrigerant level is low and
needs to be topped up. The presence of a few bubbles is
however allowed, especially in the case of high-glide ternary
mixtures such as HFC R407C
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Also check that the end-of-evaporation temperature shown
on the pressure gauge (refer to the pressure gauge scale
for the refrigerant R407C, marked with the initials D.P. - Dew
Point) is about 4 °C lower than the temperature of the water
leaving the evaporator.
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Make sure the overheating of the cooling fluid is limited to
between 5 and 8 °C: to this end:
1)
read the temperature indicated by a contact thermometer
placed on the compressor intake pipe;
2)
read the temperature indicated on the scale of a pressure
gauge likewise connected to the intake side; refer to the
pressure gauge scale for the refrigerant R407C, marked
with the initials D.P. (Dew Point).
The degree of overheating is given by the difference
between the temperatures thus determined.
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Make sure that the Sub-cooling of the cooling fluid is
limited to between 3 and 5°C: to this end:
1)
read the temperature indicated by a contact
thermometer placed on the compressor intake pipe;
2)
read the temperature indicated on the scale of a
pressure gauge connected to the liquid inlet at the
condenser outlet; refer to the pressure gauge scale
for the refrigerant R407C, marked with the initials B.P.
(Bubble Point).
The degree of Sub-cooling is given by the difference
between the temperatures thus determined.
Warning: all THN units are charged
with R407C. Any top-ups must be
made using the same type of
refrigerant. This operation is to be
considered extraordinary
maintenance work and must be
performed by qualified personnel only.
Warning: the refrigerant R407C
requires “POE” polyolester oil of the
type and viscosity indicated on the
compressor rating plate.
For no reason should oil of a different
type be introduced into the oil circuit.
Real P
compressor
outlet
Average T
(T1+T2)/2
T1 (start of condensation)
DEW POINT
T2 (end of condensation)
BUBBLE POINT
Heat content h
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The difference between the Dew Point and Bubble Point is known as “GLIDE” and this is a characteristic property of
refrigerant mixtures. If pure fluids are used, the phase change occurs at a constant T and thus the glide is equal to zero.
