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5.3 Description Standard System Components
Coolant Circuit
The pump draws coolant from the reservoir and circulates it to the process and returns it to
the evaporator. It is in the evaporator where the heat is transferred from the coolant to the
refrigerant. Adjusting the amount of heat transferred in the evaporator controls the
temperature of the coolant being delivered to the process. There is a freezestat sensor and
flow switch (optional) in the coolant circuit to serve as safety controls. There is also a
thermocouple to sense the temperature of the coolant being delivered to process and
communicates this temperature to the microprocessor based PID temperature controller. An
adjustable bypass valve allows the chiller to operate with sufficient flow through the
evaporator even if the flow is restricted or completely shut off through the process.
NOTE: Closing the bypass valve off too far may result in a situation that could damage
components in the chiller. The main purpose of the bypass line is to avoid deadheading of the
pump and reduce the possibility of an evaporator freeze-up. See Section 7.8 for more
information on adjusting the bypass valve.
Refrigerant Circuit -Advanced Refrigeration Control Circuitry (ARCC)
The OTC Series Chillers features our “Advanced Refrigeration Capacity Control” (ARCC)
circuitry. This patented circuitry allows the unit to operate from “zero load to full load”
(without cycling the compressor) while providing excellent temperature stability. Another
benefit is the ability to operate over a very wide temperature range.
The patented refrigeration control circuitry adjusts and controls the flow of refrigerant in
response to the process load. The circuitry provides only the needed cooling capacity.
Because of this innovative circuitry, the refrigeration system compressor will operate when
the unit is on regardless of whether or not the process calls for cooling. This is normal and is
not a cause for concern. Continuous compressor operation reduces wear and tear
associated with frequent cycling which can lead to premature compressor failure.
The heat that is transferred in the evaporator from the coolant to the refrigerant is used to
change the state of the refrigerant from a liquid to a gas. After leaving the evaporator, the
refrigerant passes to the compressor.
Compressor
The OTC Series Chillers are equipped with a hermetic reciprocating or hermetic scroll
compressor, depending on model. Both the compressor and the motor are encased together
and solidly mounted in the cabinet. The compressor is unidirectional and will only pump
refrigerant when properly phased. The cool refrigerant suction gas cools the motor windings,
and there is an internal thermal overload to protect the windings from overheating. The
compressor is lubricated with oil that travels throughout the system with the refrigerant.
NOTE: The compressor on OPTI TEMP OTC Series chillers runs continuously regardless of
load on the system. This is normal and not a cause for concern.
Air Cooled Condenser
This component is only used in the air cooled chillers. The condenser is constructed of heavy
gauge copper tubing and aluminum fins for maximum heat transfer capabilities. The
condenser has been generously sized so the chiller can operate with full cooling capacities in
ambient air temperatures of up to 95°F (35°C). When the ambient air temperatures are above
95°F (35°C) the chiller will lose approximately 1% of its cooling capacity per 1°F (0.5°C)
above 95°F (35°C). The chiller should be able to operate with ambient temperatures of up to
110°F (43°C). The fan(s) draw the air flow through the condenser and blows the warm
discharge air through the chiller cabinet and out the other side. The fan(s) are designed to
draw sufficient air flow through the chiller as long as there are no obstructions. The fan(s) are
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