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To 1. Temperature control machines with classcial float
The most common and known type of level monitoring is the mechanical float. The float
swims on the surface of the thermal fluid in the bath, and leads to a switching system.
Depending on the level of the thermal fluid, the electronics will either signalize an
OK
state
(with sufficient filling of the thermal fluid) or a
non OK
state
(with insufficient
filling of the thermal fluid). The float system function should be checked from time to
time. In order to do this, whilst in standby mode, push the float in the bath downwards
with a tool (e.g. screw driver). The electronics should then trigger an alarm.
To 2. Temperature control machines with electronical low-level protection (ELO)
ELO: Electronic over-temperature and low-level protection in combination
Some temperature control machines (depending on the model) possess an electronic
over-temperature and low-level protection. Instead of a mechanical float switch
temperature sensors are mounted on the surface of the heating coils to monitor the
over-temperature at a potential ignition source and to ensure that the critical
temperature at the heating coils (burn point of the thermal fluid) is controlled by the
controller (not valid for chillers, liquid level is determined by electrical capacity) via the
graphical display (60) error message will be given out.
A mechanical tool is no longer required to change the over-temperature settings. The
over-temperature switch can only be adjusted after the user has re-entered a code
displayed on the CC-Pilot´s display (60). This procedure avoids unintentional changes
being made to the setting and replaces a mechanical tool by software.
A new feature is the
Process Safety
function. This function provides further protection
for the operators and application. A classic over-temperature device unit would trip and
cause a shutdown if over-temperature cut-off temperature was reached. This could
occur under circumstances where more heat was being generated by a process
(exothermic) than the unit could remove. Switching the temperature control unit off
would remove the only possible method of cooling the application down. Consequently,
the temperature would be able to further increase, creating a risk of injury to personnel
or damage to the application, for example by over-heating a liquid into pressurised
vapour.
Using the
Process Safety
function, the controller recognises when the over-temperature
cut-off is reached, and switches the cooling on. The compressor automatic is
automatically set to
always on
. Even if the temperature continues to rise, the
refrigeration machine will increase its cooling to maximum to minimise the heating.
Please also note chapter on
Setting the
over-temperature (OT) switch
.
