Airwell MQL 15 [35/40] Maintenance
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Airwell MQL 15 [35/40] Maintenance

Airwell MQH 10T [35/40] Maintenance
Page 34
Maintenance
9.8 Thermostatic expansion valve
(Only MQL-MQH 4-8)
The circuit of the unit is equipped with a thermostatic
expansion valve, with external equalizer.
The valve is shop-calibrated for an overheating of
5°C.
Procedure to check for overheating:
– Measure the suction pressure with the pressure
gauges on the board of the unit o using a pressure
gauge connected to the service valve on the suc-
tion side.
– From the pressure gauge’s temperature scale, mea-
sure the saturated suction temperature (Tsa) which
corresponds to the pressure value.
– Using a contact pressure gauge affixed to the out-
let fitting of the gas of the evaporator, measure the
actual temperature (Tse).
Overheating calculation (S):
S = Tse - Tsa
Overheating is regulated through the thermostatic
expansion valve.
Make the adjusting screw follow a complete turn,
and operate the appliance for five minutes.
Check again and, if necessary, repeat the regula-
tion.
If the expansion valve cannot be regulated, it is prob-
ably broken, and shall be replaced. The replace-
ment must be carried out by a Service Centre.
9.9 Evaporator
Check at regular intervals that the water side of the
heat exchanger is perfectly clean. To do this, mea-
sure the pressure drop, water side (see Section 8) or
measure the temperature of the liquid leaving and
entering the heat exchanger, and compare it to the
evaporation temperature.
To obtain an effective heat exchange, the difference
between the temperature of the leaving water and
the saturated evaporating temperature must be in the
2 - 4°C range. A greater difference would indicate a
low efficiency of the heat exchanger (i.e. the heat ex-
changer is dirty).
In this case, the heat exchanger must be subjected to
chemical cleaning, an operation that shall be carried
out by authorised engineers.
For other maintenance operations (extraordinary
overhauling, replacement of the heat exchanger
etc.), contact an authorised Service Centre.
Manuale MQL-MQH 10.6.2005 12:26 Pagina 34

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