Rivacold MH-HT, Use And Maintenance Handbook

Page: 17 / 72

MH TH Pag. 17 REV. 08 11/07
UK
Drawing. 2
Drawing. 3 Drawing. 4
5. 2 Suction line insulation
With an evaporating temperature lower than -10°C, the suction line pipes must be insulated with an
anti-condensate pipe that has a thickness of at least 13mm in order to limit its overheating.
5. 3 Oil return
All systems must be designed so as to ensure oil return to the compressor.
In the situation shown in Drawing. 3 (condensing unit placed above the evaporator), it is important
to fit siphons along the suction line every 2 m of difference in height so as to guarantee oil return to
the compressor. In any case, along horizontal stretches it is important for the suction line to have a
slope of at least 3% towards the compressor.
5. 4 Adding oil
In the majority of installations where all piping is no longer than 10 m, it is not necessary to add oil.
However, when the pipes are oversized compared to standard conditions or they are longer than
10m, a small quantity of oil must be added.
5. 5 Vacuum
For the correct operation of the refrigerating equipment and the duration of the compressor, it is
very important for the vacuum in the system to be set correctly. This will ensure that air and above
all, humidity contents are below the permitted values. The introduction of new gas types has meant
the use of new polyester-type oils that have high-level hygroscopic characteristics and which require
more attention when setting the vacuum. We would advise setting the vacuum on both sides of the
circuit. In any case, the target value is a pressure no higher than 5 Pa.
Important: in order to avoid irreparable damage to the compressor, never start it in vacuum
conditions and without the gas charge
.
During the vacuum and charge procedure, remember to energise the solenoid valve coil of the
liquid line