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Freeze Protection
One or more of the ambient freeze avoidance methods
in the table below must be used to protect the chiller
Protects to
ambient
Method
temperature
Water
Pump
Control
Down to -20°F
AND
Heaters
Varies. See Low
Evaporator
Freeze
Refrigerant Cutout,
Inhibitor
Glycol
Requirements.
Drain
Water
Below -20°F
Circuit
AC-SVX001A-EN
Notes
•
Heaters alone will provide low ambient protection down to -20°F (-29°C), but will NOT
protect the evaporator from freezing as a result of charge migration. Therefore, it is
required that water pump control be used in conjunction with heaters.
•
Heaters are factory-installed on the evaporator and water piping and will protect them from freezing
•
Install heat tape on all water piping, pumps, and other components that may be damaged if exposed
to freezing temperatures. Heat tape must be designed for low ambient temperature applications. Heat
tape selection should be based on the lowest expected ambient temperature.
•
Tracer® UC800 controller can start the pump when freezing conditions are detected. For this option the
pump must to be controlled by the Stealth unit and this function must be validated.
•
Water circuit valves need to stay open at all times.
•
Water pump control and heater combination will protect the evaporator down to any
ambient temperature provided power is available to the pump and the controller. This
option will NOT protect the evaporator in the event of a power failure to the chiller unless
backup power is supplied to the necessary components.
•
When no chiller operation is possible and the pump is already off, UC800 pump control for freeze
protection will command the pump to turn:
ON if average of the evaporator entering water temperature, the evaporator leaving water
–
temperature, and the evaporator refrigerant pool temperature is less than Low Evaporator
Refrigerant Temperature Cutout (LERTC) + 4°F for a period of time.
–
OFF again if the evaporator refrigerant pool temperature rises above the LERTC + 6°F for a period
of time.
Note: Time period referenced for ON and Off conditions above is dependent on past running
conditions and present temperatures measured.
–
ON if entering OR leaving water temperature< LWTC for 30°F-sec (17°C-sec)
–
OFF again if water temperature > LWTC for 30 min
•
Freeze protection can be accomplished by adding sufficient glycol to protect against freezing below the
lowest ambient expected.
•
Use of glycol type antifreeze reduces the cooling capacity of the unit and must be
considered in the design of the system specifications.
•
Shut off the power supply to the unit and to all heaters.
•
Purge the water circuit.
•
Blow out the evaporator to ensure no liquid is left in the evaporator.
from ambient freeze damage. See RF-PRB002*-EN for
more information.
I I n n s s t t a a l l l l a a t t i i o o n n M M e e c c h h a a n n i i c c a a l l
35
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