Lennox INNOV DM R Series, Application Manual

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INNOV@ CENT -AGU-0912-E . 18 .
7.4 Checking the refrigerant level (DX version)
D 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.
D
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.
D 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.
D
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 condenser outlet 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 INNOV@ units are charged with dry nitrogen and you must empty them before
charging with refrigerant.
Warning: Any top-ups must be made using R407C only. 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.
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.
Average T
(T1+T2)/2
T1 (start of
condensation)
DEW POINT
T2 (end of condensation)
BUBBLE POINT
Heat content h
P
Real P
compressor
outlet
R407C