Protecting Cooling Towers from Freezing
Cooling tower operation is often required in freezing weather for either comfort air conditioning in the central core of a large building, or for industrial processes. Cooling towers need to be protected from freezing when the condenser loop is satisfied – meaning when the temperature setpoint is reached – or when the building is shut down for the evening.
Cooling towers need heat tracing to prevent critical pipes from freezing. Typical designs require a temperature between 40 and 45 degrees Fahrenheit. Typical control methods utilize an ambient-sensing t-stat, thermistor or RTD to monitor the outside air temperature, thus ensuring the Heat Trace System will energize whenever the outside air temperature falls below setpoint. Control options range from simple dedicated ambient t-stats to microprocessor-based controllers depending on the level of control/monitoring required by the application. Also, basin heaters prevent cold water basin freeze-up during winter weather and should be checked prior to the winter season.
Using Low Ambient Control in A/C Units
A low ambient control (LAC) is useful when high internal heat loads dictate operation in the cooling mode during colder outdoor temperatures. Examples of this could be in an electrical room, telecommunications building or loaded computer room applications. Extended operation of the compressor in the cooling mode when the outdoor temperature is less than 65 degrees Fahrenheit can cause the indoor coil to freeze up. The low ambient control cycles the outdoor fan motor in response to refrigerant pressure and conditions. This keeps the system pressures from reaching the condition where icing would occur. Because the outdoor fan “cycles,” it may appear to the end user that the condenser motor is defective and trigger a service call.
An example of when LAC is used is cooling a server room with an air cooled condenser and DX evap. Fan cycling, fan speed control and hot gas bypass are all means of controlling the head pressure. Basically, it artificially increases the head pressure to maintain a high enough high side pressure to keep the low pressure side from getting too low and causing a freeze up on the evaporator.
As Joey Donithan, Journeyman Service Technician for Crockett Facilities Services, commented, “Preventive maintenance is essential to eliminate unnecessary HVAC shutdowns or emergency service calls due to freezing temperatures. By planning upfront and implementing a preventive maintenance schedule for your HVAC equipment, you’ll be protecting your investment and not have to worry about burst pipes in cooling towers or costly repairs.”
Crockett Facilities Services – Helping Business Owners and Property Mangers to Keep Tenants Comfortable and Lowering Energy Usage
As a commercial HVAC and mechanical contractor, Crockett Facilities Services helps building owners, property managers and facility engineers to lower their operating expenses and energy costs through preventive HVAC maintenance. Whether you need mobile HVAC services for installations and repairs, or on-site facilities engineering services, we can augment your existing facility staff to meet your needs.
Give us a call to set up an appointment to make sure your HVAC equipment is properly maintained to operate in cold, freezing temperatures. To learn more about our HVAC Preventive Maintenance Programs and costs, please contact Crockett Facilities Services (CFSI) at 202.600.2787, sales@crockett-facilities.com or complete our online form for a free quote. We’re In This Building Together! Like us on Facebook; follow us with our weekly blogs on LinkedIn, Twitter, and Google+.