Airwell AQL 50 [41/63] Maintenance
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Airwell AQL 50 [41/63] Maintenance

Airwell AQL 50 [41/63] Maintenance
Page 40
Maintenance
7.8 Sight Glass
The sight glass is used to observe the liquid refriger-
ant flow and to find out if there is some humidity in-
side it. If there are some gas bubbles in the liquid
flow, it means that the dryer filter is clogged or that
the refrigerant charge has partially leaked out.
A coloured indicator is arranged inside the sight
glass. If you compare its colour with the chromatic
scale arranged on the external ring of the sight
glass, you may find out if there is some humidity in
the refrigerant. If the humidity content should be too
high:
h
Discharge the circuit and collect the refrigerant.
The circuit shall be then vacuum-purged and
recharged.
7.9 Thermal Expansion Valves
The refrigerating circuits of the AQL/AQH units are
equipped with a thermal expansion valve complete
with an external equaliser. This valve is calibrated at
works to ensure 5 K overheating.
Act as follows to control overheating:
Read the suction pressure by using a manometer
connected with the filling valve on the suction side.
Use the thermometric scale of the manometer to iden-
tify the Tsa saturated temperature corresponding to
the pressure you have measured.
Measure the Tse effective suction temperature by us-
ing a contact thermometer arranged on the attach-
ment at the outlet of the evaporator gas.
Overheating is calculated as follows:
S = Tse – Tsa
Or use the Menu function
Overheating can be changed by acting on the cali-
brating screw of the thermal expansion valve. Turn
this screw clockwise to increase overheating. Turn it
counterclockwise to decrease overheating.
The valve shall be calibrated again by turning the
calibrating screw by one revolution at a time and
then by operating the unit for 5 minutes. After this pe-
riod of time has elapsed, check overheating and cor-
rect it again, if required.
The thermal expansion valves of the AQH
models shall be calibrated with the utmost
care since every circuit of these units has
got one single thermal expansion valve
which is used both in cooling and in heat-
ing mode.
If the thermal expansion valve can not react to the
overheating calibration, it means that it is not operat-
ing correctly and that it shall be replaced. The ther-
mal expansion valve may be only replaced by an
Authorised Service Centre.
7.10 Refrigerant / Circulating Fluid
Exchanger
The cleanness of these exchangers on the water side
shall be checked at regular intervals. This can be ac-
complished by checking the load loss on the water
side (see Chapter 9) or by checking the difference
between the incoming and outgoing fluid tempera-
ture and by comparing these values with the evapo-
ration temperature.
The difference between the outgoing fluid tempera-
ture and the evaporation temperature shall lie be-
tween 5 and 7 K to enable the heat exchange to oc-
cur optimally. A greater difference means that the ex-
changer is not working optimally since it is dirty.
In these cases, this exchanger shall be chemically
cleaned by the personnel authorised by the manufac-
turer.
Contact an Authorised Service Centre for any other
type of operation (extraordinary maintenance, re-
placement of the whole exchanger, etc.).
Contact an Authorised Service Centre for any other
type of service (extraordinary maintenance, replace-
ment of heat exchangers, etc.).

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