DCE80-100E
Technical Handbook
Air conditioning unit
Service
14
P.Group 10
TDCE01
04GB
The liquid refrigerant should be completely evaporated before it
is allowed to flow from the evaporator. The refrigerant is still cold
even when it has completely evaporated. The cold vapour which
flows through what remains of the evaporator continues to
absorb heat, and then becomes overheated. This means that the
temperature of the refrigerant has risen to above the point where
it evaporates without changing the pressure.
In an evaporator which operates at a suction pressure of 2 bar,
the liquid refrigerant will have a temperature of –1.1°C. When the
refrigerant is subsequently evaporated through heat absorption
in the evaporator, the temperature of the gas will rise at the evap-
orator outlet to +1.6°C. This represents a difference of 2.7°C be-
tween the evaporation temperature and the temperature at the
outlet. This is called overheating.
All expansion valves should be adjusted at the plant in such a
way that maximum evaporation with overheating is performed in
the air conditioning system.
Checking the air conditioning unit
If the unit is in continuous operation, this check should be carried
out every week from early spring to late autumn and during ex-
tended periods of high humidity during the winter.
If the unit is used very little during cold and dry winter periods, the
compressor should be run for a few minutes every week, to lubri-
cate the rubber hoses, couplings, seals and shaft seal.
1. Start the engine and start the air conditioner.
At an outdoor temperature below 0°C, the system cannot
start since the low-pressure relay breaks contact.
2. After 10 minutes of operation, check that no bubbles are
visible in the sight glass of the filter-dryer. (Bubbles should
occur only when the compressor is started and stopped.)
If there are any air bubbles, subsequent filling should be per-
formed by an authorised service mechanic.
3. Check that the condenser is not clogged. If necessary, clean
the condenser fins with compressed air.
4. Change the fresh air filter as necessary.
5. Check the V-belt tension and the compressor mounting.
6. Check that the magnetic coupling engages and disengages
satisfactorily.
7. Check that the condensate drain from the cooling element is
not clogged. Check for leakage.
8. On certain machines with air conditioning system, there are
two hoses for draining of condensate from the condensor.
The hoses can be found on the underside of the cab’s front,
see illustration.
9. Check that the hoses are hanging so that there can be no
water accumulation. A bend can create a water lock which
will prevent the drainage.
WARNING!
z If the refrigerant hose should fail or if
other refrigerant leakage should oc-
cur, switch off the air conditioner im-
mediately.
z Refrigerant is injurious to the skin and
eyes.
z Never release refrigerant in an en-
closed space. If released into a serv-
ice pit, for instance, the gas may
cause asphyxia.
z It is forbidden by law to discharge re-
frigerants into the air intentionally.
z Never carry out welding on a charged
refrigeration system or in its vicinity.
z Only authorised service mechanics
are allowed to drain off and fill refrig-
erant in the air conditioning system.
Only the prescribed refrigerant may be
used when refilling.
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