D
–EIMAC00708-16EN - 31/76
To assure oil return to the compressor also at partial load do not use suction piping in the upward direction with size
above 2” 1/4" for full load cooling capacity in the range 100-150 kW; above 2” 5/8 for full load cooling capacity in the
range 150-
200 kW, above 3” 1/8 for full load cooling capacity in the range 200-300 kW.
If necessary, use double suction riser constructions.
Make sure to install a sightglass in the liquid line as close as possible to the expansion device of the evaporator
Expansion valve
Expansion valve has to be designed accordingly to the unit cooling capac ity and pressure drops across the liquid line
and the evaporator distributor.
In the following the reference values of condensing pressure
ST Version
Design point (35°C ambient, 7°C suction) :
14 barg
Max
:
18.5 barg
Min
:
9.0 barg
LN Version
Design point (35°C ambient, 7°C suction) :
15 barg
Max
:
18.5 barg
Min
:
9.0 barg
The expansion valve may be either thermostatic or electronic. In the case of electronic expansion valve, it has to be
equipped with standalone controller and instrumentazione.
Electronic expansion valve installation is suggested when the operating range of the chiller (and in particular of ambient
temperature) is quite wide and when low saturated suction temperature are expected.
Refrigerant Chargie
Pre-charge of refrigerant may be evaluate accordingly to the following formula
Refrigerant charge [kg] =unit charge as per technical specification tables + ld * Fl + sd * Fs + Ve * 0.5
ld = value in table 14
sd = value in table 14
Fs
= total length of the field suction line (m)
Fl
= total length of the field liquid line (m)
Ve
= refrigerant volume of the field evaporator (liter)
Table 14
– Refrigerant charge for (m) of Liquid ans suction line line
Liquid
Piping
Size
ld
Suction
Piping Size
sd
1" 5/8
1.30
3" 1/8
0.076
1" 3/8
0.93
2" 5/8
0.053
1" 1/4
0.61
2" 1/4
0.035
7/8
0.36
1" 5/8
0.021
3/4
0.26
1" 3/8
0.015
The calculated refrigerant precharge has to be added befor starting the unit (running compressor may damag e the unit).
After precharge and prestart checks, the charge has to be tuned.
For fine-tuning of the refrigerant charge, the compressor must operate at full load (100%).
The charge has to be adjusted to have suction superheat and subcooling within allowable range and to have the
sightglass totally sealed. As long as the liquid-line sightglass is not sealed, add refrigerant in steps of a few kgs and wait
until the unit runs in stable conditions. The unit must have the time to stabelize which means that this charging has to be
done in a smooth way.
During charge tuning verify the oil sightglass.
Note down the superheat and subcooling for future reference.
Fill out the total refrigerant charge on the unit nameplate and on the refrigerant charge label supplie d with the product.
