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Q)
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Why use a H.S.T. (high starting torque compressor)?
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A)
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In a system fitted with an expansion valve, when the compressor
stops a pressure difference is maintained across the compressor.
To overcome this pressure a higher torque compressor, normally
fitted with a capacitor, is required.
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Q)
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When can a L.S.T. (low starting torque compressor) be
used?
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A)
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If the system is fitted with a capillary tube, when the compressor
stops the pressures have time to equalise before the compressor
has to start, therefore the compressor motor has a lighter
load.
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Q)
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Where can the H.B.P. (high back pressure) compressor be
used?
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A)
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As the power absorbed by the compressor increases with a
rise in evaporator pressure, to allow the compressor to operate
at the higher evaporator pressures a larger motor is fitted.
Typical applications are Air conditioning, dairy cabinets
& water coolers. Using this type of compressor on a freezer
(L.B.P.) would cause the motor to overheat and have a reduced
life.
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Q)
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Where can the L.B.P. (low back pressure) compressor be
used?
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A)
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In applications such as freezers the evaporator operates
at a low pressure. Under these conditions the compressor power
requirement is low and therefore can operate with a smaller
motor. Using this type of compressor on say a dairy case (H.B.P.)
would overload the motor resulting in premature failure.
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