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Introduction
Operation
Thermo Fisher Scientific
Appendix E
Air Conditioner
This section applies to the Stulz air conditioner used on Prima PRO
and Sentinel PRO instruments. The manufacturer's documentation
must be consulted along with these notes.
The air conditioner is responsible both for cooling and maintaining a
constant temperature within the instrument enclosure.
Warning! The following potential hazards are present within the air
conditioner enclosure:
The basic operation of the air conditioner is fairly conventional. The
Normal
refrigerant fluid is compressed and passed through a condenser
section where excess heat is allowed to dissipate to ambient air
resulting in a liquid. The liquid is then allowed to vaporise in an
evaporator section within the enclosure to provide cooling, before
being returned to the compressor. There are a number of points to
note about the operation of the unit.
1. Internal air circulation over the evaporator and through the
instrument enclosure is provided by a fan (mains voltage) that
operates continuously.
2. The compressor is located within the envelope of the instrument
enclosure (not externally, as is more common). For hazardous
area operation, this allows the electrical parts of the compressor
and associated wiring to be protected by the enclosure purge,
removing the need for a hazardous area rated compressor.
3. Temperature control of the instrument enclosure is not achieved
by switching the compressor on/off - in normal operation the
compressor runs continuously. Instead, a valve in the refrigerant
circuit is used to bypass the condenser section, i.e. when the
valve is energised (open) the cooling function of the unit is
turned off. As the valve can be switched relatively rapidly, very
good temperature control can be achieved (typically better than
±1˚C with a cycle time less than two minutes). Normally, a
'click' can be heard as the valve operates.
mains voltages (some exposed terminals)
fan (no guard) – may start unexpectedly
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
E-1
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