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8.5.1 Operation
The bath controller automatically switches off cooling when the bath is oper
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ated above 50°C to protect the system from extreme pressures. The refrigera
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tion system is also protected by a brownout and over voltage protection device
that switches off power to the system when the line voltage is outside the safe
operating range. The display indicates “LoLinE” when this condition exists. A
time delay prevents the refrigeration from restarting for a short time after ade
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quate line voltage has been restored.
8.5.2 Important Refrigerant Information
The refrigeration system in this bath has been designed to perform at ultra-low
temperatures. As a result, aspects of the design are uncommon and the refrig
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erants are non-standard.
The system is cascaded, meaning there are two separate systems with the first
one chilling the second. This is required to reach temperatures below –40°C.
Normal refrigeration does not use a cascading technique, and many refrigera-
tion technicians are not familiar with such systems.
The first stage refrigerant is an HFC known as R-507. The second stage per-
forms the ultra-low cooling. Its refrigerant is an HFC R-508B, also known as
SUVA-95.
What this means to you:
• The cascade system is complex and its uncommon nature means that
many local refrigeration service technicians may not be able to service it.
If your bath needs survice, call GE Kaye Instruments Customer Service at
1-800-964-KAYE
•
The compressor manufacturer does not warranty their compressors when
used with non-standard refrigerants. Warranty of these compressors must
be handled through GE Kaye Instruments only. There is no other way for
you to receive parts or service on your compressor. You must receive your
parts or service from GE Kaye Instruments.
8.6 Temperature Controller
The bath temperature is controlled by a special digital temperature controller.
The controller features a 24-bit analog-to-digital converter (DAC) that gives it
remarkable accuracy and stability.
The bath temperature is monitored with a platinum resistance sensor in the con
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trol probe. The controller uses a proportional-integral-derivative (PID) algo
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rithm to determine how much heat the bath needs. The bath is heated by a
solid-state relay (SSR) controlled 500W heater.
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8 General Operation