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© STULZ S.p.A. – all rights reserved EN/06.2016/i01
WPA ExPlOrEr OrIGINAl INSTrUCTIONS
During the compressor pause delay (see "7.2 First-Startup" at page 63) step wise open the
shut-off valves RG3-RG4 until you reach a suction pressure thr 0,5 bar (check by suc-
tion pressure gauge). If the LP switch still trips after the elapsed evaluation delay and after hav-
ing reached the calculated suction pressure (1,6 bar), you must turn the adjustment screw coun-
terclockwise to reduce the pressure hysteresis.
8.3.8 Expansion valve
The refrigerant circuit is equipped with a electronic expansion valve, which controls the super-
heating in the evaporator. The superheating is adjusted to 5 K at the factory and may not be
modified. Check the superheating set-point.
Check the superheating by the C2020 electronic controller. If the superheating should be not
below 3 K or above 7 K,, the function of the expansion valve is faulty.
Compare the suction gas temperature measured by the valve sensor, with the value of a refer-
ence sensor at the suction line. If the superheating still diverges significantly from the set-point
and you can find no deviation at the verifications, probably the control module of the valve is
defective and must be replaced.
The expansion valve can freeze, if the humidity in the refrigerant circuit is excessive. Check the
sight glass.
WArNING
Do not thaw by soldering flame, danger of explosion! Thaw with moist warm cloth. Check the
sight glass.
8.3.9 Compressor
To be checked: compressor, crankcase heater
In the compressor there is an ester oil charge, which does not
have to be renewed under normal operation conditions and holds
out for the unit's lifetime. However, it is possible that the ester oil,
as it reacts hygroscopically, has taken up humidity of the air after
repeated recharging of the refrigerant circuit due to repair works.
The interaction between ester oil and water results in the forma-
tion of acid. Owing to a hyperacidity, corrosive processes take
place inside the compressor. In this case the ester oil should be
exchanged.
The oil level can be checked by looking at the sight glass of the
compressor or in the oil balance pipe.
Oil level
Check the oil level at the oil sight glass. During unit idleness the
oil level should not be below the lower quarter (bottom line) and
not rise above the upper line during operation.
Crankcase heater
Check the crankcase heater function by measuring the ohmic resistance at the terminals of the
