Johnson Controls Sabroe SAB 193 L, Руководство пользователя, Страница: 51 / 171

Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
008831 en 2020.10
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Technical description
4.19 Requirements for ambient temperatures and humidity
Sabroe compressor units are generally designed for indoor installation within these limits:
Humidity :
• 10-90% relative humidity (not condensing).
Temperature :
Minimum 0°C (+32F). Limiting factors:
• Avoid freezing of water charge systems during standstill
• For seamless performance, UniSAB III requires an ambient temperature above 0°C
• Be aware that some electrical panels may require a minimum temperature of +15°C.
M40°C (+104F). Limiting factors:
• Most motors have limits of m40°C, unless otherwise specified
• Centa rubber couplings are derated at higher temperatures.
Equipment for operation outside the above-mentioned temperatures is available on request.
Precautions to avoid condensing of refrigerant in undesirable places
Condensing of refrigerant outside the condenser, for example in oil separators and compressors,
is associated with a risk of damaging the equipment due to liquid hammering, reduced lubrication
and other malfunctions. In principle, condensing takes place whenever the temperature of the
equipment gets below the saturated pressure. To mitigate this risk, all Sabroe refrigeration equip-
ment is, as standard, equipped with:
• Heating element(s) in the oil reservoir on all screw compressor units
• Heating element(s) in the crankcase on all reciprocating compressors.
These heating elements are normally capable of keeping the oil temperature at least 10K above
the ambient temperature. Despite the above precautions, however, undesirable condensing is still
a risk if the ambient temperature falls significantly (10-15K) below the system condensing tem-
perature. If this happens, it should be monitored if the oil temperature stays above the saturated
temperature of the refrigerant. If it does not, these additional precautions must be taken:
• Check that standstill heating is active
• Increase timer on Oil return start-up delay to ensure boiling off condensate before oil is
returned to the compressor
• Increase the ambient (machine room) temperature
• Add insulation and, if required, heat tracing.
In any case, on systems located outdoors, or in unheated buildings where the ambient tempera-
ture may drop below 0° C [+32° F], insulation and heat tracing of the compressor lubricating oil
systems, including oil lines, oil filters, oil pumps and oil coolers, is mandatory. Freeze-up protec-
tion must also be provided for all water-cooled equipment.
For heat pumps , the risk of undesired condensing is substantially higher. Factory-built equip-
ment has a number of built-in measures to avoid this (see Technical Information TI 2016-04 and
TI 2016-05). For site-built systems, it is the obligation of the contractor to install similar and ad-
equate means to avoid undesired condensing.
Suction check valve power assistance is not necessary on check valves with linear ball bearings.