Installation and Maintenance Manual

Installation Mechanical
RTAE-SVX001B-EN 29
Freeze Protection
One or more of the ambient freeze avoidance methods in
Table 15 must be used to protect the Stealth chiller from
ambient freeze damage.
Table 15. RTAC freeze avoidance methods
Method
Protects to
ambient
temperature Notes
Water Pump Control
AND Heaters
Down to -20°F
• 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 Inhibitor
Varies.
See “Low
Evaporator
Refrigerant Cutout,
Glycol
Requirements,”
p. 30
• 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.
Drain Water Circuit Below -20°F
• 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.
NOTICE:
Evaporator Damage!
If insufficient concentration or no glycol is used, the
evaporator water flow must be controlled by the UC800
AND heaters must be used to avoid catastrophic
damage to the evaporator due to freezing. It is the
responsibility of the installing contractor and/or the
customer to ensure that a pump will start when called
upon by the chiller controls. Refer to RLC-PRB012-EN.
Even with water pump control, a power loss of as little
as 15 minutes under freezing conditions can damage
the evaporator. Only the proper addition of freeze
inhibitor or complete drainage of the water circuit can
ensure no evaporator damage in the event of a power
failure.