Refrigerant Connections On Air Cooled Units; Choosing The Diameter Of The Discharge Tube - Trane MERCURY EDAB 1105A Technical Manual

Refrigerant connections on air cooled units

Installation guide
WARNING! The pipes must always be protected from the sun.

Choosing the diameter of the discharge tube

The discharge line must be sized in such a way that it guarantees the flow of oil, in particular when operating at partial
load, avoiding the return of the condensate refrigerant to the head of the compressor and prevent excessive vibration and
noise due to the pulsations of hot gas, vibrations of the compressor, or both.
Even if it would be preferable to have low losses of the load along the line, an oversized discharge line is necessary to
reduce the speed of the refrigerant so that it does not provoke a reduction in its speed and therefore reduce the flow of
oil. Moreover, when the machine uses more compressors for the cooling circuit, the discharge line must transport the oil
at all operating levels.
The minimum diameters needed to guarantee the flow of oil can be found in Graphics 1 -2 for the horizontal and vertical
lines respectively.
In the installation of machines which have more compressors per circuit, the vertical discharge line, sized in order to
guarantee the flow of oil at minimum load, may cause excessive loss of load when operating at its maximum level; in this
case it is possible to use pipes with a larger diameter together with an oil separator.
The loss of load along the discharge line causes an increase in the condensing temperature and therefore a decrease in the
cooling capacity of the conditioner. Please note that each percentage point of decrease in the cooling capacity corresponds
to a decrease of 1°C of the maximum operating temperature. Normally the systems are sized in such a way that the loss
of load from the discharge line does not cause a decrease in the efficiency of the machine of more than -3%.
The responsibility of establishing the refrigerant line between the condensing unit and the external unit lies
with the installer.
22 PKG-SVX19B-E4