Air Cooled Products CGAM, RTAC, RTAF, ACR, ACS
If during the process of being serviced and service work is interrupted or delayed, the chiller should be hermetically sealed, evacuated and charged with 5 – 10 psi of dry nitrogen until the service can be completed.
If a chiller has not been installed, please follow the Storage Requirements as called out in the IOM.
If a chiller has been installed and the startup will be delayed, follow the Storage Requirements as called out in IOM. If water is in the water loop and has been running through the chillers heat exchanger; the main concern is a heat exchanger ambient freeze.
Freeze Avoidance for Air-Cooled Chillers
When dealing with air-cooled chillers, it is crucial to implement effective freeze avoidance strategies to prevent damage and ensure optimal performance. The appropriate method for freeze avoidance will depend on the geographical location of the jobsite. Below are three recommended options:
- Continuous Pump Operation: Keeping the pumps running ensures that the chilled water or glycol solution remains in motion, preventing it from freezing. This method is particularly effective in regions where temperatures occasionally drop below freezing but do not remain low for extended periods.
- Use of Freeze Inhibitors: Adding a freeze inhibitor, such as glycol, to the chilled water system can lower the freezing point of the solution. This method is suitable for areas with moderate freeze risk. Ensure that the concentration of the inhibitor is adequate for the expected minimum temperatures.
- System Draining: In locations where prolonged freezing temperatures are expected, or if the system will be inactive for an extended period, draining the chilled water solution from the heat exchangers is the best option. This prevents any risk of freeze damage to the system components.
Geographical Considerations
The location of the jobsite plays a significant role in determining the best freeze avoidance method. For instance, south of the Mason-Dixon Line (approximately Latitude 39 degrees, 43 minutes), freeze avoidance is generally less of a concern, especially during this time of year in the USA.
Best Practices
- Avoid Stagnation: It is essential to prevent treated or untreated water from becoming stagnant in the heat exchangers, as this can lead to severe damage. Regular circulation of the solution helps maintain system integrity.
- Monitor Ambient Conditions: If the pumps will not be running and there is a risk of ambient temperatures causing the solution to freeze, draining the system is the safest option until startup can be performed.
By following these guidelines, owners can effectively manage freeze risks and ensure the longevity and reliability of air-cooled chiller systems.
Example of Freeze Avoidance Section within the IOM
Freeze Avoidance
One or more of the ambient freeze avoidance methods in table below must be used to protect the Sintesis™ chiller from ambient freeze damage.
Table 17. RTAF freeze avoidance methods
Method Protection Range Notes Water Pump Control and Heaters Down to -4°F • Heaters alone will provide low ambient protection down to -4°F (-20°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. Water Pump Control and Heaters Down to -4°F • Heaters are factory-installed on the evaporator and water piping and will protect them from freezing. Water Pump Control and Heaters Down to -4°F • 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. Water Pump Control and Heaters Down to -4°F • Symbio™ 800 controller can start the pump when freezing conditions are detected. For this option the pump must be controlled by the Sintesis unit and this function must be validated. Water Pump Control and Heaters Down to -4°F • Water circuit valves need to stay open at all times. Water Pump Control and Heaters Down to -4°F • Water pump control and heater combination will protect the evaporator 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. Water Pump Control and Heaters Down to -4°F • When no chiller operation is possible and the pump is already off, Symbio™ 800 pump control for freeze protection will command the pump to turn: Water Pump Control and Heaters Down to -4°F ON if the respective circuit’s LERTC Integral was seen to be >0 for a period of time. The LERTC integral is increased if the Evap Refrigerant Pool Temp is below the value of the Low Evap Rfgt Temp cutout + 2°F. Water Pump Control and Heaters Down to -4°F OFF if respective Evap Rfgt Pool Temp rises 4°F above LERTC setting for 1 minute and Chiller Off LERTC Integral = 0. Water Pump Control and Heaters Down to -4°F Note: Time period referenced for ON and Off conditions above is dependent on past running conditions and present temperatures measured. Water Pump Control and Heaters Down to -4°F ON if entering OR leaving water temperature < LWTC for 30°F-sec (1.11°C-sec) Water Pump Control and Heaters Down to -4°F OFF if both entering and leaving water temps rise 2°F above the LWTC setting for 5 minutes. Freeze Inhibitor Varies. • Freeze protection can be accomplished by adding sufficient glycol to protect against freezing below the lowest ambient expected. Freeze Inhibitor Varies. Important: Be sure to apply appropriate LERTC and LWTC control setpoints based on the concentration of the freeze inhibitor or solution freeze point temperature. Note that these settings vary with unit size. See “Low Evaporator Refrigerant Cutout and Glycol Requirements,” p. 43. Freeze Inhibitor Varies. • For units with free-cooling option, glycol solution is REQUIRED. See “Free-Cooling Fluid Management,” p. 76. Freeze Inhibitor Varies. • 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 -40°F • Shut off the power supply to the unit and to all heaters. Drain Water Circuit Below -40°F • Completely drain water from evaporator and exposed water piping not otherwise protected from freezing. See “Water Treatment,” p. 28 and “Waterbox Drains and Vents,” p. 30. Drain Water Circuit Below -40°F • Blow out the evaporator to ensure no liquid is left in the evaporator and water lines.
Water Cooled Products RTWD/UD and RTHD
If in the process of being serviced and service work is interrupted, the chiller should be protected from developing internal corrosion. If the refrigerant/charge has been removed, but still hermetically sealed, evacuate the chiller and charge the chiller with 5 – 10 psi dry nitrogen.
If a chiller is in the process of being dissembled, follow the procedures as called out in RLC-SVB41*-EN & RLC-SVG003*-EN for RTWD/UD chillers or RTHD-SVB02*-EN for RTHD chillers.
For new chillers that have not been installed, please follow the Storage Requirements as called out in the IOM.
For new equipment that has been installed and the startup will be delayed, follow the Storage Procedures as called out in the IOM as well. If protective shipping coverings have been removed, they should be reinstalled until the chiller is commissioned. It is best to NOT let treated or untreated water become stagnate in the heat exchangers (severe damage may occur).
Products
- ACR (air-cooled)
- ACS (air-cooled)
- CGAM (air-cooled)
- RTAC (air-cooled)
- RTAF (air-cooled)
- RTHD (water-cooled)
- RTWD (water-cooled)
- RTUD (water-cooled)
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.