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Table 31 List of the most common faults in the operation of the cooling system of CM and HPM sets
Failure type Cause Removal
Temperature behind the air
cooler too high
- Incorrectly adjusted thermostatic valve
- not enough medium provided to the cooler
perform appropriate adjustment
polluted lter - the dehydrator on the cooler supply (pollution) of the installation is visible on
the sight glass by changing colour of the INDICATOR
replace the lter with a new one
faulty thermostatic valve replace with a new one
air cooler oiling
remove oil from the radiator by reducing overheating
on the thermostatic valve
Too frequent switching on and
o of the cooling compressor
too little airow: dirty air lters clean or replace with new ones
frosting the cooler
cooling medium evaporation temperature too low
set the correct evaporation pressure with the
(injection) control valve
too little airow: dirty air lters clean or replace with new ones
Cooling medium leakage leaks on screwed or welded joints on ttings locate the leakage point and seal it
9. Design and installation recommendations
9.1 General recommendations
a) In case of a short distance between the unit and the air
intake or a system of ducts that creates the possibility of
spontaneous inow of cold air to the unit during standstill, it
is recommended to install an additional damper which can
be closed during standstill on the inner wall of the air intake,
b) Drain and vent valves, thermometers and pressure gauges
should be installed near the water supply systems for the wa-
ter heat exchangers,
c) For heaters, it is recommended to use a Ø15 by-pass control
valve with a manual control valve or adjustable orice, so that
the residual ow of the heating medium through the heater
can be maintained during frosty periods.
d) When the unit is operating at temperatures lower than the
freezing point of the medium in the not working exchangers,
it should be emptied of the medium. After draining the water,
the exchanger should be blown with compressed air in order
to remove the remaining freezing substances.
9.2 Recommendations for water heaters
It is recommended to use heating water of so called low
parameters 90/70ºC, in case of supplying the heaters with
water of high parameters it is necessary to use high-pressure
ttings (min. 1,6MPa) and work in counter-current.
9.3 Recommendations for the automation designer
Elaboration on typical automation systems can be found in
separate studies.
9.4 Protection of water heaters against freezing
It is recommended to use systems that protect water heaters
from falling below the freezing temperature of the medium.
9.5 Protection of electric heaters against overheating
It is recommended to use a system that controls the air ow
through the electric heater. It should be possible to switch o
the electric heater when the safety thermostat is activated and
when the air ow decreases.
9.6 Basic dependencies in operation of ventilation and air-condi-
tioning units
a) when mechanical intake and outlet ventilation is com-
bined, the operation of the intake and outlet fans is coupled
b) start and stop time of the fans, set on the frequency con-
verter, should be minimum 30s
c) If the air ow through the unit stops, the heating water
supply should be cut o by the control valve on the supply.
Only the residual ow of the medium is allowed.
d) Operation of the humidier and electric heater is only al-
lowed during air ow through the device,
e) the supply of the cooler with direct evaporation is only
allowed with air ow through the device.
f) In roof units, for external dampers, higher protection class
IP54 minimum must be used.
g) The unit’s automation system should enable the device
to be switched o in the event of the facility’s re protection
system activation.
Power supply of the heaters in the absence
of air ow may cause damage to the unit.
This applies especially to electric heaters.
Opening the supply of cooling medium to the
cooler in the absence of heat load can damage
the compressor.
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