When a thermostat in a refrigeration system detects its pre-set temperature it switches off the
compressor. If after a short period the door of the cooler is opened, the thermostat may achieve its
switch on temperature very quickly. As there still may be high pressure in the outlet side of the
compressor, an extremely high torque is required to restart the system. If the compressor is a non-
capacitor start type then this may cause the system to switch off on its thermal overload protection. If
this occurs it can take as long as 5 – 10 minutes before the thermal overload is restored. If the
compressor is a capacitor (assisted) start type then the capacitor will provide the extra current needed
to push through the existing pressures. However, the (unwanted and damaging) peak current will be
conducted through the windings of the compressor. If however the pressures in the system are
allowed to equalise then an early restart is prevented. Therefore the peak current drawn by the
compressor would be kept to a minimum value.
AUTOMATIC DEFROST MANAGEMENT
To avoid “icing-up” of the cooler, the EMS automatically performs a periodic off cycle defrost
depending upon the setting of parameters DE (defrost intervals) and DD (defrost duration). However,
if the defrost cycle occurs during a high traffic period i.e. frequent door openings of the cooler, then
the defrost cycle will automatically be terminated. This termination is based upon the temperature in
the appliance and can be adjusted by parameter Dt (defrost termination temperature). The
combination of frequent defrosts and the mode change from operational to stand-by will avoid the
cooler icing up.
Keeping the evaporator of a cooler free of ice/frost development enhances the heat exchange and
maintains the efficiency of the refrigeration system. If required a manual defrost can be performed by
pressing the defrost button for 5 seconds. If the cabinet temperature is above the termination
temperature then a manual defrost is inhibited.
VOLTAGE MANAGEMENT PROTECTION SYSTEM
Under voltage and to a lesser extent over voltage is damaging to an electric motors windings. The
EMS is programmed with a Voltage Management Protection System to avoid unnecessary damage to
the compressor when the appliance is installed in areas where the supply voltage is unstable. The line
voltage centre differs around the world and therefore the switching levels are programmable to ensure
that the EMS is suitable for worldwide use. When the system has switched off due to high voltage the
display shows the letters “SHI” (supply high) and when switched off due to low voltage the display
shows the letters “SLO” (supply low)
Please note that the EMS-55 does NOT rectify the voltage but merely monitors it and switches the
refrigeration system on and off if the supply voltage falls below or rises above, the limits programmed
in parameters HI and LO.
Below is the table with the value details for HI and LO parameters for the various voltages used
throughout the world.
110V - 120V Line voltage
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