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EN/06.2016/i01 © STULZ S.p.A. – all rights reserved
WPA ExPlOrEr OrIGINAl INSTrUCTIONS
6.3 refrigerant circuit
As a protection against over pressure the refrigerant circuit is equipped with a safety valve on
the pressure side of the compressor.
If attaching pipework to a relief valve, the pipes must have a sufficient diameter so as not to
cause resistance to the operation of the valve. For critical or complex installations refer to EN
378, unless it is not specified by local regulations, the internal diameter can be calculated using
the following formula:
D
5
= 1.447
x
l
D
: Minimum pipe internal diameter in centimetres
l
: Length of pipe in meters
6.4 External water circuit
The basic chilled water circuit of the chiller contains an evaporator, a differential pressure switch,
temperature sensors in the inlet and outlet, a pressure gauge and vent valves. In addition to this,
the free cooling version disposes of a motor driven 3-way control valve and another temperature
sensor in the chilled water circuit. For a detailed overview, please take a look at the circuit dia-
gram in chapter "4.5 Hydraulic diagrams" at page 30.
The frost protection sensor measures the temperature of the liquid and reports it to the control-
ler in which a threshold for an antifreeze alarm is defined. This value is adjusted on 4°C in the
factory. Below this water inlet temperature it releases a frost protection management by the
controller, which may lead to an antifreeze alarm. The adjusted value of 4°C can be modified and
has to be adapted to the local conditions (glycol content).
If the water temperature passes under 5°C or if the outside temperature is less than 2.5°C, it is
mandatory to add the following quantities of ethylene glycol (indicated as percentage of weight
of the water quantity):
Ethylenic glycol
External temp.
%
from +5 to -5°C
10
from -5 to -10°C
20
from -10 to -15°C
28
from -15 to -20°C
35
from -20 to -25°C
40
INFOrMATION
Prepare the required water/glycol mixture outside of the chilled water circuit and fill the
circuit later
