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EN/06.2016/i09 © STULZ S.p.A. – all rights reserved
WSA ExplOrEr OriginAl inStructiOnS
To exchange the filter drier it is sufficient to evacuate the pipe section in which the filter drier is
installed.
Close the shut-off valve (RU1 or RU2, see “4.4 Piping diagrams” at page 25). The expansion
valve is closed when the compressors are switched off. By the service valve on the lid of the fil-
ter drier, you can evacuate the refrigerant from the section now.
Remove eight M8 screws at the front side of the filter and pull out the cartridge. Introduce a
new cartridge and refill the evacuated refrigerant.
Open the shut off valves RU1 and RU2.
Adjustment screw
Adjustment lock
HP switch with reset button
LP switch with automatic reset
8.3.6 Hp switch
To be checked: high pressure switch
When the
High pressure
limiter triggers, the compressor is
switched off without delay. Before the restart and after the elimina-
tion of the error, the HP switch must be reset by pressing the reset
button. You can change the action value only after having removed
the adjustment lock. Turning the adjustment screw counter-clock-
wise reduces the action value.
A check of the tripping function of the high pressure limiter (e.g. by
cutting down the condenser fan and forcing a high pressure) is not
possible without changing the action value, as there are, on behalf
of the C2020 electronic controller, further monitoring functions
via the high pressure sensor, which intervenes in the compressor
control (high pressure management, compressor envelope control).
A change of the action value (e.g. by reduction), however, bears
the risk that this one is not exactly readjusted after the check has
been executed. The scale on the case does not provide sufficient
accuracy.
8.3.7 lp switch
To be checked: low pressure switch, shut-off valves RU1-RU2
Check the correct function of the low pressure switch by stepwise
closing the shut-off valve RU1-RU2 on the refrigerant circuit, while
the compressors are running. Check by means of the low pres-
sure gauge in the compressor section, whether the low pressure
switch trips at 0,4 bar. When the LP switch trips, the compressor
is switched off without delay. If the pressure switch has tripped
too early (e.g. at 2,0 bar), you can reduce the threshold by turning
counter-clockwise the adjustment screw on the top side of the
pressure switch after having removed the adjustment lock.
During the compressor pause delay (see “7.2 First Startup” at page 69) stepwise open the
shut-off valves RU1-RU2 until you reach a suction pressure thr 0,5 bar (check by
suction pressure gauge). If the LP switch still trips after the elapsed evaluation delay and after
having reached the calculated suction pressure (1,6 bar), you must turn the adjustment screw
counter-clockwise to reduce the pressure hysteresis.
