Temperzone UC8 Troubleshooting Guide
High suction line / evaporating temperature protection
Protects the compressor motor from overheating.
If the unit has a variable duty compressor (digital scroll or variable speed) then high suction pipe /
evaporating temperature protection is applied only when capacity is at 50% of nominal duty or higher.
If the unit has a fixed duty compressor this protection is always applied.
Conditions: When the evaporating temperature remains above +27.5°C (1665 kPa, 241.5 PSI)
and/or the compressor suction pipe temperature remains above +30°C for longer than
15 minutes.
Low discharge side superheat protection
Protects a unit with an electronic expansion valve (EEV) from prolonged flooding of the compressor
which otherwise might cause damage to the motor bearings or to the compression stage.
This protection does not apply to units that use accurators.
Discharge side superheat is defined as the difference between the compressor discharge pipe
temperature and the condensing temperature.
Conditions for units with fixed duty compressor:
When discharge side superheat remains below 10K for longer than 15 minutes.
Conditions for units with variable duty compressor (digital scroll and variable speed types):
At nominal duty and higher: When discharge side superheat remains below 10K for longer
than 15 minutes.
Between standard minimum and nominal duty: Minimum discharge side superheat varies
linearly with capacity from 0K at standard minimum duty to 10K at nominal duty.
At standard minimum duty and below: Protection not applied.
Standard minimum duty: 40%
Nominal duty: 100%
High discharge side superheat protection
Protects a unit from prolonged running with a lack of refrigerant or where the compressor remains
otherwise starved of refrigerant. Applied only when the unit operates in normal mode, not applied
when a unit is de-icing the outdoor coil.
Discharge side superheat is defined as the difference between the compressor discharge pipe
temperature and the condensing temperature.
Conditions: When discharge side superheat remains above 45K for longer than 30 minutes.
Freeze protection
Protects against freezing of the circulating water.
Applies to hydronic reverse cycle units when the unit is heating the room and thus cooling the water.
Also applies to chillers when the unit is cooling the water.
Conditions: When the compressor suction pipe temperature remains below 0°C for longer than 1
minute or when the evaporating temperature remains below -4°C for longer than 1
minute.
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