Thermostatic Expansion Valve; Evaporator - Johnson Controls CWP Manual De Instalación Y Mantenimiento

Maintenance
If you compare the colour of the indicator to the scale
on the ring of the sight glass, you can calculate the
percentage of humidity of the refrigerant. If it is ex-
cessive, replace the filter's cartridge, operate the ap-
pliance for 1 day and then check the humidity %
again. When the humidity % is within the pre-deter-
mined range, no other operations are required. If the
humidity % is still too high, replace the dehydrating
filter again, start the unit and operate it for another
day.

9.8 Thermostatic expansion valve

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
3.5-5°C to R407C. A greater difference would indi-
cate a low efficiency of the heat exchanger (i.e. the
heat exchanger is dirty).
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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.