tion
4
3.3 Temperature indication, control, and safety circuit
The equipment is provided with a 7 segment LCD-Display (3
½
places) with additional symbols for
indicating bath temperature and settings as well as operating states. The setpoint can be input and
additional adjustments can be made using either two or three keys.
A Pt 100 temperature probe is used for measuring the actual temperature and for control. A second Pt
100 serves as independent temperature probe for the safety circuit (overtemperature protection) which is
independent of the control function
A low-level cut-out switches off the heating on both poles in order to prevent dry operation of the heater.
The pump is switched off through the electronics. The setting of the overtemperature cut-out is adjusted
with a tool on a potentiometer and is always limited to 5°C above the operating temperature range.
All settings and fault messages are stored in the memory in case of a supply failure or when the mains
switch is set to OFF.
The tubular heater is controlled from a modified PID controller through a triac circuit specially designed
to be unaffected by supply variations and interference.
3.4 Materials
All parts which come into contact with the bath liquid are made from high-grade materials appropriate to
the operating temperature. These are rust-free stainless steel, PPS plastics and fluoride rubber.
3.5 Refrigeration system
The refrigeration system consists essentially of a hermetically sealed compressor. Heat of
condensation and motor heat are dissipated by a fan-cooled finned condenser. Fresh air is drawn in
at the front of the unit, warmed air is discharged at the back and to the sides. The ventilation
openings must not be restricted in order to ensure proper air circulation.
At working temperatures below approx. 30 °C the refrigeration system operates continuously to
remove a certain amount of heat, with the heater acting in opposition to provide automatically
controlled heating power.
The compressors are fitted with a temperature monitor which responds both to the compressor
temperature and to the motor current. In addition the cooling system is protected against excessive
pressure by a pressure monitor. The refrigeration unit is switched on either automatically or
manually through the operating menu .(
➾
Section 6.4.1.).
When the fault circuit is activated the refrigeration system is also switched off.
Cooling curves
(
➾
Section 9. Technical data)
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